VRLA batteries are stands for Valve Regulated Lead Acid Battery .It was born in the 1970s , in some developed countries have formed a considerable scale of production , and soon formed the industrialization and mass market . While the battery is lead-acid batteries , but it is compared with the original lead-acid battery has many advantages , but users much welcome , especially those who need the battery equipment mounted together ( or a workstation ) user favor such as UPS, telecommunications equipment, mobile communications equipment, computers and motorcycles .
Because VRLA batteries are sealed and will not leak acid , and during charging and discharging is not like the old-fashioned lead-acid batteries that will be put out of the mist and corrosion of equipment , pollute the environment, so that people from the structural characteristics of the VRLA battery also known as closed ( sealed ) lead-acid batteries . In order to distinguish between the old-fashioned lead-acid battery called the opening lead-acid batteries . Because VRLA battery from a structural point of view , it is not only sealed , but there is a gas pressure inside the battery can control a valve , so the full name of VRLA lead-acid battery has become the " valve- sealed lead-acid batteries ."
People also collected accurate kinetic information about the oxidation state S + side reaction of sensitizers to study the influence on the stability of dye-sensitized solar VRLA Battery.Since the oxidation side reaction rate constant is much smaller than the regeneration rate constant Bi 8, the key parameter is that the ratio K0x / KKG < 1 between the oxidation side reaction rate constant and the regeneration rate constant can easily generate the oxidation state S + of the sensitizer, and the life of the oxidation state S + can be independently determined by the infrared absorption spectrum.Recent research data on Z - 907 showed that the formation of oxidized S + occurred in 810 min immediately after the addition of oxidant.The subsequent decay occurred during the life of 75 min, corresponding to the rate constant of side reactions in the oxidation state.X=2.2xi（r4s^1。The regeneration rate constant of the sensitizer in a typical R / IR redox medium is at least 2x105 s', so the side reaction branching ratio in the oxidation state is about 10 _ 9, which is lower than the above-mentioned limit requirement of 10 _ 8, so that a turnover of 100 million times and a dye life of 20 years can be achieved.
A large number of long-term tests have been carried out on N3 Ru complex and the unusual stability of this charge transfer sensitizer has been repeatedly confirmed.For example, a project funded by a European consortium [ 45 ] has confirmed that the stability of photogenerated current of dye-sensitized solar VRLA Battery after 2.5 solar and 10000h photoaging is equivalent to 5.6x107 turns of dye without any significant attenuation.These results confirm the above prediction based on dynamics.A more challenging task is the extended thermal stress stability test at 8085 C.Recently, in order to stabilize the interface, the dye-sensitized solar cell has successfully met the stability index designed for outdoor application of crystalline silicon solar cell for the first time by using sensitizer self-assembly combined with hydrophilic lipophilic co - adsorbent.For example, the new hydrophilic lipophilic sensitizer K - 19 showed an increased extinction coefficient due to the expansion of hydrophobic bipyridyl K co-rolling and the presence of an electron donor alkoxy group.With the increased light absorption of this new sensitizer and DPA as a co - adsorbent, a new electrolyte formulation can be formed, achieving a conversion efficiency of > 8 % for dye-sensitized solar VRLA Battery, and striking stability can be achieved through prolonged thermal stress testing and light aging treatment testing [ 9 ].
In an 80 C environment, sealed dye-sensitized solar VRLA Battery are used to extend thermal stress tests.Actual. 17 shows that the open circuit voltage w of this device has only decreased by 25mv after aging at 80 c for 1000 h.By contrast, the open circuit voltage of devices dyed with K - 19 dye alone will drop by about 70mV.DPA's stabilizing effect is attributed to the formation of a strong and compact molecular monolayer on the surface of mesoscopic TiO 2 film, thus reducing absorbed moisture and other harmful impurities.By stabilizing the open circuit voltage, the conversion efficiency can be kept at a certain level in the extended thermal stress test.Actual. 17 shows that after aging at 80 C for 1000 h, the device can still maintain the initial conversion efficiency of 98 %, no significant change in fill factor FF is observed, and the measured short-circuit current density JSC = 15.38 mA / cm2, even higher than 15.16 mA / cm2
Initial value.The reverse trend of short-circuit current density and open-circuit voltage VOE reflects the slight positive shift of straight band of mesoporous TiO _ 2 film under prolonged thermal stress, which will improve the photocharge separation efficiency of dye-sensitized solar VRLA Battery.
The surface of the dye-sensitized solar cell is covered with a 50 - thick polyvinyl acetate film provided by British Preservation Equipment as an ultraviolet cut - off filter with an upper limit of 400 cm.The sample was irradiated with 100 MW / cm2 of Suntes TCPS + Xenon lamp from Atlas at the open circuit and 60 C temperature.Actual 18 shows.The dye-sensitized solar cell samples were tested under the dual conditions of 60 C prolonged thermal stress and visible light aging treatment for 1000 h, and the conversion efficiency remained 97.7 % of the initial value, with short-circuit current density of human.From the initial value of 15.15 mA / cm2 to 15.53 mA / cm2, the open circuit voltage decreased by 16mV and the filling factor decreased by less than 3 %.This once again confirmed that the phenylethylene unit attached to the bipedal ligand has photochemical inertness to photoaging treatment.
In recent years, dye-sensitized solar VRLA Battery have attracted wide attention from the industry, and the development of commercial components has also progressed rapidly.Dyes OL in Australia, G 24 Innovation in Britain, Aisin Seiki in Japan, RWE in Germany and Solaroix in Switzerland are well-known dye-sensitized solar cell companies.Dyes OL has successfully produced large-area components for field testing, and several buildings have already installed these components.Aisin Seiki and Toyota have also started the sample production of dye-sensitized solar VRLA Battery.The red dye is n - 719, while the black dye is rul' 3, l, = 2, 2', 2 " - terpyridyl 4, 4', 4" tricarboxylicacid.The monolithic design uses carbon as the interconnect and cathode material, which can reduce costs.
At the Aichi Prefecture Expo in Japan, Toyota Dream House installed a dye-sensitized solar cell developed and produced jointly with Aisin Seiki as a glass curtain wall.
Research and development trends
Through full-color and infrared - absorbing dyes and surface modification, light collection in the 700900 nm range can be achieved, and the conversion efficiency of dye-sensitized solar VRLA Battery can reach more than 12 %. Another promising method is to use the concept of stacked VRLA Battery, and select appropriate top and bottom VRLA Battery to absorb human light in visible and infrared light bands, respectively.Our laboratory has recently studied and prepared such a laminated VRLA Battery with a conversion efficiency of 15 %
The idea of solar photovoltaic conversion using organic materials has a long history and has been a hot research direction for decades.Organic materials are usually low in cost and easy to prepare, and their properties can be adjusted by molecular design and chemical synthesis.The highly polarizable TV - conjugated system of organic molecules is the most important performance of organic solar VRLA Battery.Although the electronic structure of organic materials is different from that of typical inorganic crystal materials, the nonlocal 7T - conjugated system makes the properties of organic materials close to those of inorganic semiconductors:
Light absorption and radiation in the visible and near infrared spectral range;The change range of conductivity is wide, which can be close to the conductivity of insulator or metal.Can transport charge at macro distance.
In, Chinese - American scientist Dr. Deng Qingyun W first demonstrated an organic solar cell with a conversion efficiency of about 1 %.This organic solar cell is based on a two-layer structure of two known photoconductors: Me - PTCDI ( N, N - Dimthyl - Pery Lene - 3, 4, 9, 10 - Dicarboximide ) and ZnPC ( Zinc - Phtalociyanine ), both of which are relatively inefficient photovoltaic materials when used as single-layer structures.This is because the charge generation efficiency in organic materials is generally very low and the mobility of carriers is relatively low, with the average free path being less than the coulomb radius F2:
In the formula, the relative dielectric constant e of the organic material is smaller.
Therefore, the photoluminescence in organic materials mainly forms a bound neutral excited state, with bound energy from 0.04 eV to 1 eV [ W ], and the generation of free carriers requires a certain excess energy to achieve electron transport from the excited donor to the acceptor or lower molecular orbital at the interface.The concept of multi-layer small molecule solar VRLA Battery has been studied all the time, and the laboratory conversion efficiency record exceeds 3.5 % [ 5 ].
Since the conductive polymer was discovered in 1977 [ 6 ], its metal or semiconductor properties, easy preparation process and softness similar to ordinary plastics have attracted extensive research interest [ 7 ].First, the conductive polymer diode successfully prepared in 1987 was based on soluble P3HT ( poly ( 3 - hexythiophene ) ), sandwiched between transparent conductive oxide TCO and evaporating AI contact electrode, thus opening up the field of plastic electronic devices [ 8 ].It is expected that the conductive polymer can be used to prepare several novel electronic devices, enter the electronic application market by virtue of low-cost materials, preparation costs and flexible and light properties, and replace the existing electronic devices:
Flat panel display technology based on organic light emitting diode OLED;Integrated electronic circuit technology formed by polymer-based field effect transistor ( FET ) [ 10 ];Fully organic solar VRLA Battery [ 11 ].
The conjugate polymer and fullerene ( fullerene or buckminsterfullerene, cm ) form an interpenetrating network, and the concept of the formed bulk heterojunction solar cell belongs to a completely organic solar cell, which can also be called a plastic solar cell, and is very hopeful to realize large-scale industrialization.This chapter will focus on the rapid development of bulk heterojunction solar VRLA Battery and introduce various novel materials and advanced feature measurement techniques.
The photo-generation mechanism of bulk heterojunction solar VRLA Battery will be introduced in this section.That is, ultra-fast photo-induced charge transfer between photoexcited conjugated polymer and fullerene [ 12 ] has been observed by several optical techniques.Section 10.2 also summarizes the previous device research work.Section 10.3 discusses the operating mechanism of the most advanced bulk heterojunction solar cell, paying special attention to the optimization of nano-morphology and the improvement of spectral response.Section 10.4 uses a novel transient conductivity technique to study the carrier mobility and recombination process.First, the correlation between the chemical structure, morphology and carrier mobility of RR - MDMO - PPV is discussed.Then, the mobility of photogenerated carriers and doped induced carriers were compared. The samples were RR _ P3HT, using time-of-flight TOF technology and linearly increasing voltage and charge extraction CELIV technology.The comparison results show that TOF and CELIV, which are two different technologies in principle, can give a self-consistent conclusion of carrier mobility.Finally, photoinduced charge extraction photo - celiv technique with linearly increasing voltage can simultaneously determine the carrier mobility and lifetime of bulk heterojunction solar VRLA Battery.For bulk heterojunction solar VRLA Battery with different active layer thicknesses, some meaningful conclusions can be obtained by comparing the measured mobility and lifetime values with the corresponding volt-ampere characteristic curves.Finally, a summary is made and the future development is briefly prospected.
Photo - induced charge transfer
K - conjugated polymers have considerable semiconductor properties and excellent mechanical properties, and still retain the advantages of traditional polymers [ 7 ].Fullerene [ 13 ], or G., a new form of C, is another important functional material of bulk heterojunction solar VRLA Battery. O - fullerene is a strong electron acceptor, can carry up to 6 electrons and can form charge transport salts with several strong donors.
Put C6.and no obvious ground state interaction is observed.After the conjugated polymer donor is excited by light, the following series of reactions will begin until the charge is separated [ 14 ]:
.The various optical detection results summarized below experimentally confirm the photo-induced charge transfer between non-degenerate conjugated polymers and:
The light absorption spectrum of MeH - PPV: C60 mixture is only a simple superposition of the two components, and no ground state interaction [ U ] is observed.
In photoinduced absorption,
PIA ) results, pure MeH - PPV and MeH - PPV:.Mixed triplet - triplet absorption occurs at 1.35 eV.The triplet - triplet absorption refers to the transition from the lowest triplet state to the higher triplet state of the molecule.However, in MEH - PPV: C6.In the mixed PIA spectrum, a sharp edge of PIA at 1.1 eV and a straight curve at 1.6 - 2.0 eV [ 15 ] can also be observed.
According to photoinduced absorption detection magnetic resonance ( PIA DMR ) [ LFL, pure polymer MeH - PPV peak at 1.35 eV is attributed to triplet - triplet absorption, while MeH - PPV: CS.The triplet - triplet absorption in the mixture is completely quenched.
Since the light-induced charge transfer in the internal system of MeH - PPV is fast enough, the singlet state cannot be quenched to the triplet state, and charge transfer has already occurred, so that the absorption characteristics of MeH - PPV can be attributed to positively charged cationic groups, i.e. light doping [ 14 ].
Studies on sub - picosecond transient absorption [ 17 ] show that photo-induced charge transfer occurs within 40fs of photo - excitation, even quenching coherent vibrational excitation of conjugated polymers [ 18 ].This ultra-fast time-scale charge transfer can ensure that the quantum efficiency of photo-induced charge separation is close to 100 %.
The steady-state optical conductivity experiment shows that if the conjugated polymer is mixed with 1 % C6 (, the optical conductivity can be increased by several orders of magnitude.According to the time-resolved optical conductivity experimental data, the increased steady-state optical conductivity comes from the cumulative effect of increased charge generation and increased carrier lifetime [ 19 ].
The study of photo-induced electron spin resonance ( LESR ) has given a definite proof that photo-induced charge transfer has occurred. The energy is greater than the N band gap of the conjugated polymer and two LESR signals have been detected by photo-excitation of MeH - PPVJCGO mixture with gas.The signal of value g < 2 indicates the characteristic of go anionic group, while the signal of about 2.002 indicates the characteristic of conjugated polymer cationic group.The time-resolved LESR study also showed that the signal of charge will still be detected within hours at liquid-gas temperature, which indicates that there is a continuous optical conductivity M at low temperature.
The transient absorption TA study in NSMS time range proves that the lifetime of photogenerated carriers is long, and the kinetics of exponential relaxation means that quite a few carriers may be trapped by deeper traps [ 22 ].
The results of the above-mentioned optical detection experiment are typical ultrafast light-induced charge transfer between conjugated polymer and fullerene, and the quantum yield of charge generation is close to 100 %.Photogenerated carriers are in metastable state and have a maximum lifetime of several ms.If selective exposure is applied to the above system, a successful organic solar cell can be prepared immediately.First, the MEH - PPV layer and the evaporation CS will be spin coated.The double layer device of the layer is sandwiched between indium tin oxide ITO coated glass and A1 contact electrode [ 23 ].The planar heterojunction device shows four orders of magnitude volt-ampere characteristic rectification in the dark, short-circuit current density of several / ia / cm2 and open-circuit voltage of 0.5v, and the human light condition is 514 nm monochromatic light of about 1mw / cm2 transmitted into the ITO surface.The spectral response of the diode device shows that most of the photogenerated current is generated at the thin interface between MeH - PPV and CEO plane heterojunction.The real breakthrough comes from the interpenetrating network between the electron donor material and the electron acceptor material, extending the interface to the entire active layer, resulting in a device structure known as the bulk heterojunction [ 11 ].
Actual. 3 shows the concept and operation mechanism of bulk heterojunction.The lowest unoccupied track LUMO of the donor material transports photogenerated electrons to the lowest unoccupied track LUMO of the acceptor and is collected by the A1 negative contact electrode.The highest occupied orbital HOMO of the acceptor material transports the photogenerated holes to the highest occupied orbital HOMO of the donor and is collected by the indium tin oxide ITO positive contact electrode.
In fact, the first organic solar cell prepared by Dr. O Deng Qingyun, a chemical structure of organic materials commonly used in bulk heterojunction solar VRLA Battery, used a double-layer structure: MDMO - PPV, MEH - PPV, P3HT or PTP TB ( Poly - N - Dodecyl - 2,5 - Bis ( 2' - Thien yl ) Pyr Role - 2,1,3 - Benzothiadiazole ) is the conjugated polymer donor material of ZnPC and M PTCDO plastic solar VRLA Battery, and PCBM is often used as the acceptor material of Fuller.
In bulk heterojunction solar VRLA Battery, carriers are generated by photo-induced charge transfer.In order to achieve effective charge generation, the excimer excited by light anywhere in the mixture needs to reach the donor-acceptor interface within its lifetime.Therefore, the maximum amplitude of phase separation depends on the diffusion length of excitons.Experiments show that only a few wt % electron acceptors quench almost all excitons and emit fluorescence.
As a final step, carriers need to be extracted from the device by two contact electrodes.Glass plated with transparent ITO serves as hole contact and HOMO matching conjugated polymer serves as transparent front contact.The A1 contact electrode of the evaporated LIF serves as an electronic contact, and the LUMO matching PCBM serves as an opaque back contact.In the most advanced bulk heterojunction solar VRLA Battery, the 100nm thin hole injection layer can also smooth the ITO surface and increase the stability of the device.The internal interface film as a hole injecting human layer is usually pedot - PSS ( poly ( 3,4 - ethylenedioxybenzene ) - poly ( 4 - styrene sulfonate ).
Several solution technologies can form the active layer of bulk heterojunction solar VRLA Battery:
Spin coating [ 24 ];
Wipers [ 25 ];
Screen printing [ 26 ];
Spraying [ 27 ].
Spin coating can be easily used in academic research on a laboratory scale, and several printing techniques have realized large-sized plastic solar cell samples [ 28 ].
The main parameters that determine the solar cell conversion efficiency 7 are the open-circuit voltage Bi, the short-circuit current Lu and the filling factor FF:
In the formula, Bi is the output power of the device under illumination, and H is the human light power.
In a single-layer polymer diode, the open-circuit voltage corresponds to the work function difference between anode and cathode materials, i.e. the device can be described as a metal - insulator - metal ( MIM ) model diode 3.MDMO - PPV: The open circuit voltage VE of PCBM devices at room temperature is about 0.8V and slightly increases to about 0.9V at lower temperatures.The open circuit voltage is considered to correspond to the energy level difference between LUMO ( 4.1 eV or 4.3 eV ) of PCBM and HOMO ( 5.3 eV ) of MDMO - PPV [ 32 ].Moreover, the open-circuit voltage kx. depends only weakly on the work function of the cathode material, but appears to depend very much on the LUMO [ 33 ] of the electron acceptor.These observations show that the simple MIM model cannot explain the built-in electric field of bulk heterojunction solar VRLA Battery.In the device using Au as the cathode, an open circuit voltage of + 0.6V was observed, and the work function of Au was very close to that of ITO / PEDOT - PSS anode, so according to the simple MIM model, the built-in voltage was even close to 0V, which is obviously inconsistent with the facts.A more reasonable explanation is that the cathode work function and LUMO - induced PCBM [ 34 ] through the " Fermi level pinning" mechanism.Mihailetchi et al [ 35 ] confirmed that if materials with higher work functions such as LiF / Al and Ca than LUMO of PCBM are used as the anode, the open-circuit voltage of the bulk heterojunction solar cell is relatively insensitive, which may be due to ohmic contact with the cathode PCBM.
The work of Gadisa et al [ 36 ] verified the dependence of open circuit voltage on HOMO level in polythiophene heterojunction solar VRLA Battery.The author observed that changing the HOMO, V * of the conjugated polymer almost linearly changes with HOMO, which confirms the view that the maximum value of is also affected by the conjugated polymer HOMO.
The short-circuit current depends on the spectral sensitivity of the light-sensitive material, that is, the proportion of human light absorbed by the light-sensitive layer, and also on the charge generation efficiency and charge collection efficiency.The charge generation efficiency and charge collection efficiency of a certain material combination strongly depend on the phase separation nanotopography of light sensitive mixing, which will be discussed in section 10.3.2.
The limited photon harvesting of bulk heterojunction solar VRLA Battery can only be overcome by using novel materials, so that materials with smaller band gaps can absorb light in a longer wavelength range.The latest progress in improving light harvesting in bulk heterojunction solar VRLA Battery will be discussed in section 10.3.3.
Finally, the fill factor FF is strongly affected by the carrier mobility lifetime product.In order to improve the filling factor FF of bulk heterojunction solar VRLA Battery, a feasible way to improve carrier mobility in conjugated polymers is to use region-regular polymers, which will be discussed in Section 10.4.
Influence of Nano - topography
Nano - morphology of Bulk Heterojunction
If the solvent used to cast the active layer is simply changed, the conversion efficiency of the 1: 4 body heterojunction solar cell based on the wt % of MDMO - PPV: PCBM can be improved from about 1 % ( AM 1.5 ) to 2.5 % M ..Atomic force microscope AFM observed that toluene cast film would form relatively large particle clusters of 100200 nm, while chlorobenzene cast film would form smooth surface morphology.TEM and AFM studies [ 37 ] attributed large particle clusters to PCBM - rich phases.After increasing the concentration of PCBM, the phase separation of MDMO - PPV: PCBM mixture from chlorobenzene spin coating was studied in more detail [ 38 ].In order to observe samples in three dimensions, not only AFM and TEM, but also time-of-flight secondary mass spectrometer ( TOF - SIMS ) was used to dynamically observe the depth distribution of samples.When the concentration of PCBM is as high as 50 % 60 %, AFM and TEM experiments show a very smooth film morphology.At a higher concentration of PCBM ( > 67 % ), the film surface began to become uneven and two phases could be identified on the corresponding tem image.The darker growth with the increase of PCBM concentration is considered to be a relatively pure PCBM phase, which is similar to the reference [ 37 ].The distribution of deuterated PCBM derivative D5 - PCBM on the film thickness was studied by TOF - SIMS.The uniform distribution of D5 - PCBM can be observed under various D5 - PCBM concentrations and film thicknesses.The electrical characteristics of different MDMO - PPV: PCBM mixtures in the light and in the dark were also studied, and the enhancement of photogenerated current and conversion efficiency in the range of 50 % 70 % PCBM concentration was observed.All in all, PCBM with a concentration of about 80 % in the polymer matrix can achieve the best device performance, because nano-scale phase separation improves electron transport and reduces bimolecular recombination.
Hoppe et al recently reported the study of nano-scale morphology details of photosensitive layer by AFM and SEM [ 39 ].The SEM images of chlorobenzene casting films were compared, and the wt % ratio of MDMO - PPV: PCBM was 1: 2, 1: 4 and 1: 6, respectively, so it was considered as PCBM phase, which is similar to the reference [ 37, 38 ].However, nanospheres with small size and high brightness exist in various thin film samples under study.In the toluene casting film, the nanospheres are " thin skins" that wrap the particle clusters.In chlorobenzene casting film, nanospheres are uniformly distributed.The size of nanospheres does not seem to depend on solvent type and PCBM concentration.The authors believe that the high brightness nanospheres are MDMO - PPV phase, in which the polymer chain has a winding structure.This view is supported by annealing experiments.In the annealing experiment, the difference of different phases is improved because PCBM has the tendency of diffusion and crystallization.PCBM particle clusters were replaced by larger voids, indicating the diffusion movement of PCBM to the crystallization center.However, the nanospheres remain in the position before the annealing experiment.The photoluminescence of MDMO - PPV reappears after annealing, which strongly supports the view that small-sized nanospheres are MDMO - PPV polymers.
Actual. 7 is the AFM image of MDMO - PPV: PCB MWT % ratio of 1: 4 toluene cast film, with the MDMO - PPV concentration changing from 0.1 % to 0.3 %.Obviously, using a higher concentration of MDMO - PPV results in a larger size of phase separation due to the longer drying time required for thicker films.The effect of drying conditions on morphology and spectroscopy was observed earlier.
Double cable polymer
The above morphology study shows that although the preparation of bulk heterojunction solar VRLA Battery is very simple, proper control of process parameters is quite complicated, and many influencing factors need to be carefully studied: solvent selection, solution concentration, wt % ratio of active ingredients, etc.If the material combination is changed, it is obviously necessary to reconfigure the parameters.In order to control the morphology at the molecular level, the concept of " double cable" polymer was introduced [ 41 ].The key requirement for applying these materials to solar VRLA Battery is to avoid the ground state interaction between the donor part and the acceptor part, " double cables" cannot be short - circuited.The introduction of an insulating spacer between the " N" cable and the " P" cable enables the " double cable" polymer to meet such requirements.The insulating spacer can also improve the solubility of macro molecules, but the length of the insulating spacer should be appropriate so as not to hinder light-induced charge transfer.
Due to the low solubility of donor - acceptor dyad, " double cable" polymer was first produced by electropolymerization.Using electrochemical techniques, the bipolar properties of macro molecules can be clearly observed.The soluble " double cable" polymer has been chemically synthesized, and the preliminary work of " double cable" polymer material used as solar cell has also been published.The difficulty in achieving higher conversion efficiency at present is that the relatively low wt % concentration of fullerenes will limit charge transport and the solvability of the " double cable" polymer is still low [ 42 ].
Improve photon harvesting
The absorption spectrum of MDMO - PPV: PCBM mixture was compared with the spectral photon flux received on land at AM 1.5.The absorption spectrum of MDMO - PPV: PCBM mixture is limited to a spectral range of about < 1.8 ev [ 43 ].In order to improve the spectral response of bulk heterojunction solar VRLA Battery, a conjugate polymer with lower K - X - band gap is needed.The need to adjust the color of the emitted light from the conjugated polymer-based organic light emitting diode OLED has led to the development of several synthesis techniques to change the band gap of the conjugated polymer.At present, the correlation between molecular structure and band gap has been well understood, and a certain band gap design requirement M can be achieved.
Another polymer material PTP TB is synthesized by electron-rich N - Dodecyl - 2,5 - bis ( 2' - Thien YL ) Pyr Role and electron-poor 2,1,3 - Benzothiadiazole.Conjugated polymer PTP TB exhibits high efficiency photoluminescence and electroluminescence in the near infrared spectral range of about 800nm.When PTP TB and PCBM are mixed, photoluminescence is quenched, and light-induced absorption PIA experiments detect light-induced charges, which are typical absorption characteristics of polarons.The conversion efficiency of bulk heterojunction solar VRLA Battery based on PTP TB: PCBM mixture reached 1 %.The measured spectral photogenerated current and the corresponding photoelectric conversion efficiency 7pce under short-circuit condition are very close to the absorption of the co-working polymer.The spectral response of PTP TB: PCBM mixture is extended to a longer wavelength, which is 200 run higher than MDMO - PPV: PCBM mixture, and the covered solar spectrum has a larger photon flux.The relatively low fill factor FF is mainly due to the limited overall performance of these devices.
Another type of low band gap polymer worth studying is PTV ( poly ) [ 45 ].In the FET structure of the field effect transistor, PTV exhibits very high carrier mobility [ 46 ].On the other hand, PTV as a whole is not easy to dissolve.In order to overcome the solubility problem, Vanderzande et al. recently developed a precursor method for preparing bulk heterojunction solar VRLA Battery based on PTV 3,4 - dichloro and 3,4 - dibromo derivatives.A precursor polymer was synthesized by thionyl precursor method and converted into conjugated polymer PTV by medium heat treatment.The obtained PTV derivative has a band gap of 1.55 eV.Precursor polymers are easily soluble and can be deposited using conventional solution processing techniques.In order to prepare bulk heterojunction solar VRLA Battery.The film containing the mixture of precursor polymer and PCBM is converted at a temperature at which PCBM is still stable.The conversion efficiency of bulk heterojunction solar VRLA Battery based on PTV derivatives and PCBM prepared by this precursor method is about 0.2 %, which is mainly limited by smaller open-circuit voltage and filling factor.The research shows that optimizing the thermal conversion process is the key to further improve the performance, and the subsequent post-processing of diode production can improve the open-circuit voltage Voe and fill factor FF of the diode, which may be due to the reduction of shunt and pinhole of the sensitizing layer film.
The lower absorption coefficient of fullerenes in the visible spectrum also limits conjugated polymer / C6.The important problem of solar cell spectral response.This is because the lowest energy electron transition of C6Q is symmetry forbidden [ 47 ].Therefore, C6 is the main component currently used in bulk heterojunction solar VRLA Battery.Almost optically inactive.Wienk et al. have demonstrated the use of fullerenes with less symmetry, such as derivatives of PCBM ( 70 - PCBM ).Cy。The derivative remarkably improves the light absorption in the visible light band, can improve the short-circuit current of the bulk heterojunction solar cell, and, g.The absorption of derivatives at lower energy does not overlap with the absorption of conjugated polymer MDMO - PPV, so 70 - PCBM can be selectively excited inside the mixture.It has been clearly observed through the light-induced absorption PIA experiment that MDMO - PPV has the optical property of positive charge due to the photoexcitation of fullerene derivatives, which indicates the light-induced hole transfer from the photoexcited state of fullerene derivatives to the conjugated polymer.Such a charge generation mechanism has been envisaged before, but this is the first time it has been clearly demonstrated.The conversion efficiency of MDMO - PPV: 70 - PCBM solar VRLA Battery is about 3 %.Compared with the standard MDMO - PPV: PCBM solar cell, the open circuit voltage of the device is 7 = 0.77 V, and the filling factor FF = 55 %, which is a factor limiting the conversion efficiency.
The above results show that optimizing one parameter ( morphology or band gap ) may reduce other characteristics, such as carrier mobility or film formation characteristics.In order to improve the conversion efficiency of bulk heterojunction solar VRLA Battery, materials are required to exhibit all necessary properties.One of the important properties is to transport photogenerated carriers efficiently at macroscopic distances.The next section will summarize the experimental methods for determining carrier mobility and the synthesis process for improving carrier mobility in bulk heterojunction solar VRLA Battery.
Transport and recombination of carriers
Measurement Technology of Transient Conductivity
Assuming that the drift of photogenerated carriers anywhere in the effective layer of the solar cell is driven by the electric field strength F [ 4, the drift length of photogenerated carriers is:
The problem now is how to measure the mobility and lifetime r of carriers in bulk heterojunction solar VRLA Battery, and how the mobility p and lifetime r are related in the interpenetrating network between the donor material and the electron acceptor material.
First, we will demonstrate that improving the mobility of conjugate polymer carriers is a feasible way to improve the conversion efficiency of bulk heterojunction solar VRLA Battery.The carrier transport characteristics of the region regular polymer RR - MDMO - PPV ( 2 - Methoxy - 5 - ( 3,7 - Dimyloxyloxy ) - 1,4 - Phenylenylene ) can be compared with the region random polymer counterparts, and the relationship between molecular structure, morphology and carrier mobility will be focused on.Subsequently, in principle, different time-of-flight ( TOF ) techniques and linearly increasing voltage charge extraction CELIV techniques will be applied to RR - P3HT samples, and we will compare the two transient conductivity measurement techniques.Finally, we will demonstrate the simultaneous determination of carrier mobility / / and lifetime r in bulk heterojunction solar VRLA Battery using a novel linearly increasing voltage photo - induced charge extraction technique.
The pulse sequence, signal response, mobility calculation formula and principle diagram of sample thickness requirements of TOF, CELIV and Photo - CELIV technologies.In TOF technology, the sample with known thickness D is under the applied electric field strength F, and the transition time center of the two-dimensional surface photo-generated carriers through the sample drift can be determined by the measured signal response.Thus, the TOF mobility can be calculated as:
The surface photogenic conditions of tof technology require a large film thickness d and a large optical density, od > 10.The photo-generated current transient j can be described as a non-discrete platform with a well-developed signal curve.In this case, the transition time L is defined at the intersection of the platform and the transient tail of the photogenerated current.If the signal curve shows strong dispersion, the recorded photo-generated current transient j will not appear as a plateau, but will still decrease with time t.When the curve is discrete, the transition time g of the photogenerated current transient j will be defined at the intersection of the logarithmic photogenerated current with respect to the two linear regions of the logarithmic time curve [ 49 ].The electric field strength f = u / d is considered to be evenly distributed over the sample, and this condition needs to be met:
This experimental condition can be realized by selecting suitable sample thickness and other methods.Unlike TOF, CELIV technology can determine the mobility of a sample with a thickness of only a few hundred nm.
Because the band gap of most organic materials is relatively large and the number of equilibrium carriers is too small to be easily determined by CELIV, chemical doping is required to increase the number of carriers.However, short laser pulses may be used instead to generate photogenerated carriers, i.e., photo - celiv.Photogenerated carriers undergo recombination or are extracted to the external circuit by the built-in electric field in case of short circuit.However, the built-in electric field can be compensated by the forward bias cancellation voltage ( 1 / gal ) of DC, reaching the flat band condition, and photogenerated carriers are forced to meet and recombine.After the adjustable delay time k that determines the lifetime, the remaining carriers can be extracted at the reverse bias voltage ramp.Calculating mobility " using photo - celiv technology requires assuming that carriers are generated in vivo, which limits the thickness of the active layer to about 300400 nm and depends on the absorption coefficient of the excitation wavelength.
Carrier Transport in Conjugated Polymers
Conjugated polymers can be regarded as one-dimensional semiconductors, and their semiconductor properties are attributed to the extended k electron system formed by 0 conjugated backbone n, electrons.Although microwave conductivity technology [ 52' 53 ] confirms that the mobility of conjugated polymers on the chain can reach very high values, the macroscopic transport characteristics are often controlled by chain jumps of several orders of magnitude slower.By attaching the side chain to the conjugated backbone, the solubility and process feasibility of the conjugated polymer can be met.Naturally, the length of the insulated side chain will affect the inter-chain electron coupling and thus the mobility, because it has been confirmed that the carrier mobility of RR - PAT will decrease as the length of the side chain increases [ 54 ].Moreover, the regularity of attached side chains plays an important role in solid state morphology and order.For example, the region regular polymer RR - P3HT has solubilized side chains attached in a regular form and has a crystalline phase [ 55 ], while the region random polymer P3HT is typically amorphous.The electrical properties of the two materials are also very different.Region regular polymer RR - P3HT has the highest mobility among all conjugated polymers used in field effect transistor FET, while region random polymer P3HT has a lower mobility by 34 orders of magnitude [ 56' 571 ].
Martens et al. [ 58 ] studied the effect of side chain substitution on carrier mobility in a series of alkoxy - PPV.According to the measurement of carrier mobility by the space charge limiting current ( SCLC ), the mobility of symmetrical substituted OC10C10 - PPV is orders of magnitude higher than that of asymmetrical substituted area random OC 10CI 0 - PPV, i.e. MDMO - PPV.From the study of the dependence of mobility on temperature and electric field strength, it can be concluded that the increased chain-to-chain and inter-chain disorder is the main reason for the decrease of mobility of regional random polymer RRA - MDMO - PPV.
Based on the above discussion, we expect to increase the degree of regional regularity of conjugated polymers to be a feasible method to improve their carrier mobility.Lutsen and others " % recently synthesized soluble region regular polymer MDMO - PPV by thionyl precursor method [ M ].Using time-of-flight TOF technology, the charge transport characteristics of this region regular polymer can be compared with that of commercial region random polymer RRA - MDMO - PPV.
A series of MDMO - PPV copolymers can be synthesized by the sulfinyl precursor method by mixing two stereoisomers of the same monomer, monomer A and monomer B ..If the proportion of any stereoisomeric compound exceeds 80 %, the solubility of MDMO _ PPV copolymer will be greatly reduced because of the aggregation of conjugated chains in solution.X - ray diffraction measurements can further confirm the improved aggregation trend.The X - ray diffraction spectrum of MDMO _ PPV powder will show a clear reflection peak m at 3 when the area is regularly boosted n.The exact location of the peak is measured by small angle X - ray scattering ( SAXS ) and can give the chain repeat distance between polymer skeletons with separated side chains, which is about 28 people.
Since the device prepared for mobility measurement requires a high solubility of the material, we selected the wt % of monomer A and monomer B to be 70: 30 for polymerization, that is, 70: 30 MDMO - PPV, and compared its charge transport and photovoltaic properties with that of the regional random polymer RRA - MDMO - PPV.
The mobility values at room temperature were measured by time-of-flight TOF technique. The samples were 70: 30 MDMO - PPV and RRA - MDMO - PPV of different film thicknesses.Interestingly, the zero electric field strength mobility P ( f - * 0 ) of 70: 30 MDMO - PPV is larger only when the temperature is greater than 230 K, but it decreases rapidly due to greater energy disorder, and finally is smaller than the RRA - MDMO - PPV value when the temperature is less than 230 K ..
In fact, the intercept between the data line and the ordinate in .14 can determine the value of the former factor mobility species, while the slope of the data line is related to the width of Gaussian state density.The constants of the equation ( 10.15 ) can be calculated respectively. j, c' are shown in practice. I from the slope of the mobility vs ( < Tabt ) 2 curve, the fitting parameter c can be calculated.70: 30 MDMO - PPV is an order of magnitude higher than RRA - MDMO - PPV in the mobility of the former factor and slightly larger in the width of the higher state density.In addition, the dependence of mobility on electric field strength can be described by the fitting parameter C, which is only slightly larger than the RRA - MDMO - PPV value at 70: 30.The value of the fitting parameter c obtained is well matched with the theoretical calculation value c = 2.9x10 _ 4m1 / 2v - 1 / 2, with a difference of only 2 times.
Pre - factor mobility / z.It is mainly determined by the number of electronic coupling between adjacent transport points, which is a sensitive exponential function of the distance between points.The slight increase in energy disorder of MDMO - PPV at 70: 30 can be attributed to the lower energy states of ordered nanoclusters, which are lower than those of amorphous matrix and become deep energy traps for overall charge transport.This model is expressed as actual .15.Actual. 5 illustrates the movement of charge in the amorphous region of the film, and the energy of the transport point has experienced a statistical change environment.In fact. 5 describes the partially aligned regions of the conjugated chains, which will facilitate the interaction between the chains.These areas are considered to be " highways" that form carriers, thus increasing mobility.Since the electron wave function of the ordered region is considered to be more polarized, the degree of dipole induced interaction is considered to be higher in the ordered region of the film, thus reducing the energy of these points.Because the ordered regions in our model are embedded in the amorphous matrix, these lower energy states can be used as traps to broaden the state density distribution.Charge jumps at one end of these " expressways" ( indicated by large solid arrows in actual. 15 ) require sufficient thermal energy or an applied electric field to tilt the barrier.Therefore, at high temperature and high electric field strength, 70: 30 MDMO - PPV exhibits higher carrier mobility due to better inter-chain interaction.At low temperature and low electric field strength, charges may be trapped by lower energy states in the alignment region, so mobility is more dependent on temperature and electric field strength.
We believe that the interaction between RR - MDMO - PPV chains will increase, and the phenomenon that regional regularity will increase the aggregation trend supports this view.Recently, the study of thermal stimulated luminescence ( TSL ) further illustrates this problem [ 61 ].
Bulk heterojunction solar VRLA Battery were prepared with 70: 30 MDMO - PPV: PCBM and RRA - MDMO - PPV: PCBM, respectively, with a mixed wt % ratio of 1,4.Although the short-circuit current of the two devices is similar to the open-circuit voltage VU gen, the 70: 30 MDMO - PPV: PCBM mixture has a relatively high conversion efficiency due to a higher filling factor PT70 % of about 70 %.VRLA battery state-of-charge estimation in telecommunication power systems
【AH Anbuky, PE Pascoe - IEEE Transactions on Industrial …, 2000 - ieeexplore.ieee.org】Carbon reactions and effects on valve-regulated lead-acid (VRLA) battery cycle life in high-rate, partial state-of-charge cycling
【KR Bullock - Journal of Power Sources, 2010 - Elsevier】VRLA battery discharge reserve time estimation
【PE Pascoe, AH Anbuky - IEEE transactions on power …, 2004 - ieeexplore.ieee.org】High rate partial-state-of-charge operation of VRLA batteries
【PT Moseley - Journal of Power Sources, 2004 - Elsevier】Modeling the overcharge process of VRLA batteries
【WB Gu, GQ Wang, CY Wang - Journal of Power Sources, 2002 - Elsevier】Progress in overcoming the failure modes peculiar to VRLA batteries
【A Cooper, PT Moseley - Journal of Power Sources, 2003 - Elsevier】A VRLA battery simulation model
【PE Pascoe, AH Anbuky - Energy Conversion and Management, 2004 - Elsevier】Further demonstration of the VRLA-type UltraBattery under medium-HEV duty and development of the flooded-type UltraBattery for micro-HEV applications
【J Furukawa, T Takada, D Monma, LT Lam - Journal of Power Sources, 2010 - Elsevier】Development of ultra-battery for hybrid-electric vehicle applications
【LT Lam, R Louey - Journal of power sources, 2006 - Elsevier】Performance measurement and reliability of VRLA batteries
【DO Feder - … Energy Conference, 1995. INTELEC'95., 17th …, 1995 - ieeexplore.ieee.org】VRLA battery - WikipediaTalk:VRLA battery - WikipediaLead–acid battery - WikipediaDeep-cycle battery - WikipediaSilver calcium battery - WikipediaAutomotive battery - WikipediaList of battery types - WikipediaOpzs - WikipediaElectric battery - WikipediaAmazon.com: Amstron 12V 9Ah VRLA Battery - F2 Terminal ...Amstron 12V 7AH Agm Sla Battery 12 Volt 7A Rechargable VrlaBuy 12V Lead Acid Battery Charger For SLA AGM GEL VRLA ...Amazon.com: VMAX63 12 Volt 10Ah AGM SLA VRLA Battery ...ProPower 12v 7Ah Agm Sla Rechargable Vrla Battery - - Amazon.comUltratech UT-1270 Sealed Lead Acid - AGM - VRLA BatteryAJC 12V 24Ah Sealed Lead Acid - AGM - VRLA Battery - AJC Brand ...CooPower CP12-55 Sealed Lead Acid - AGM - VRLA BatteryAJC 12V 75Ah Sealed Lead Acid - AGM - VRLA Battery - AJC Brand ...CooPower CP12-7.0 Sealed Lead Acid - AGM - VRLA BatteryValve Regulated Lead Acid battery - Home | FacebookVrla Battery Lucy Hou | FacebookVRLA Battery | FacebookLead acid battery, vrla battery,agm battery - Local Business ...Mer Balds - Hi, how do we know if a VRLA battery is dead ...VRLA battery 12v 7ah == 151*65*94/100mm - FacebookGary Lau - we are a professional VRLA battery manufacturer ...Supply Lead Acid Battery, VRLA Battery,... - Huafu High Technology ...Valve Regulated Lead Acid Battery -... - MBF Solar Solutions ...VRLA battery lily (@lilyryan1212) | Twitter#vrlabattery hashtag on TwitterLA (@vrla) | TwitterSunlikeSolarBattery (@solar_batteries) | TwitterSilicone battery (@silicon_battery) | TwitterPeter Wu (@lituanwu) | TwitterAlice Xue (@temriibattery) | TwitterB.B. Battery on Twitter: "B.B. Battery has devoted on VRLA (Valve ...MPINarada on Twitter: "Narada the global leader in VRLA and ...