A deep-cycle battery is a lead-acid battery designed to be regularly deeply discharged using most of its capacity. In contrast, starter batteries (e.g. most automotive batteries) are designed to deliver short, high-current bursts for cranking the engine, thus frequently discharging only a small part of their capacity. While a deep-cycle battery can be used as a starting battery, the lower "cranking current" implies that an oversized battery may be required.
EBIC is a semiconductor analysis technology based on scanning electron microscope SEM, which relies on electron-hole pairs generated in the semiconductor by microscopic electron beams and can be used to analyze buried junction regions, defects or minority carrier characteristics of the semiconductor.
The conversion efficiency of Cu - In - Ga thin film solar DEEP CYCLE BATTERY depends on the characteristics and band gap of the absorbing layer material, and the laboratory conversion efficiency record has increased from 10 % to 20 %.The front contact of small area DEEP CYCLE BATTERY has grid lines, light loss and contact electrode loss are small, but there are no grid line components.or a DEEP CYCLE BATTERY [ 57 ] with a thinner absorption layer, these losses need to be considered.The collection of photogenerated current is close to ideal and the open circuit voltage is ￥?and fill factor ff.The Cu ( In, Ga ) S2 solar cell with band gap of 1.53 eV has a single-layer antireflection film, and the maximum external quantum efficiency EQE is close to 1.The external quantum efficiency EQE curve of short wavelength and long wavelength is limited by the band gap of ZnO window layer and Cu ( In, Ga ) S2 absorption layer, respectively.Due to the large recombination rate of holes in the N - type CdS buffer layer, holes cannot be collected effectively, and the external quantum efficiency EQE with photon energy greater than the CdS band gap is reduced % \ The larger shielding current causes loss of open circuit voltage and filling factor, and makes the diode ideal factor greater than 1.However, the shielding current of the CIGSE DEEP CYCLE BATTERY with high conversion efficiency depends on the in vivo recombination of the space charge region of the absorption layer.The diode ideal factor of 12 and its temperature characteristics are consistent with the composite analysis model described by exponential decay state density m ].Through the optical spectrum and admittance spectrum, the defect distribution of this tail state can be observed [ 65' 66 ].The typical Ulbach energy is 50 Loom eV.
The tail state is a wider defect distribution, and some narrower defect distributions are 250 - 300 mev & [ 67 ] above the valence band.This defect distribution in the band gap has been observed by different observation methods in samples obtained by different preparation methods ( even in single crystal samples ) [ 25 ].Even if the ratio of Ga 8 in + Ga ) changes, the defect distribution in the band gap will still maintain a certain relative energy level distance from the valence band in the whole CIGSE.However, the defect density is related to the content of Ga, reaching the minimum defect density at Ga / ( In + Ga ) 0.30.The loss of open circuit voltage is related to the defect density that determines trap recombination ⑽.Radiation from energetic particles can increase the defect density, while annealing at a suitable temperature after preparation can reduce the defect density.Other studies show that there is a deeper defect energy level " clipping" at 0.8 eV above the top of the valence band.This defect energy level is close to the center of the band gap of the Ga - rich material and becomes the effective recombination center of the wide band gap CIGSE absorption layer.Production, in the best performance narrow-band gap DEEP CYCLE BATTERY, reverse saturation current is completely thermally activated, the activation energy corresponds to the band gap of the absorption layer, and the diode ideal factor is slightly dependent on the temperature' open circuit voltage is also a function of temperature, satisfying the low conversion efficiency, and the cell is more affected by the tunneling effect.After observing different low conversion efficiency DEEP CYCLE BATTERY samples in different temperature ranges, it is found that the diode ideal factor is more temperature dependent.If the influence of tunneling effect is not too great, the mechanism of shielding current can be explained as trap recombination in the space charge region of the absorption layer with the help of tunneling effect [ 71 ].In this case, the activation energy of the reverse saturation current still corresponds to the band gap, and the ideal diode factor depends on the temperature.According to the measurement results [ 72 ], this model can be applied to devices with greater tunnel effect.
Although better in vivo properties can be inferred from the collection of photogenerated current, the open-circuit voltage \. of wide-band gap Cu ( in, ga ) S2 DEEP CYCLE BATTERY is lower than expected.The analysis of carrier transport shows that the main shielding current mechanism changes with illumination.Under ideal boundary conditions, the interface barrier decreases under illumination, and the tunnel effect has little effect on interface recombination.In the dark, the tunnel effect has a great influence on the recombination of space charge regions.Although this composite mechanism with light change is now observed in Cu ( in, ga ) S2 DEEP CYCLE BATTERY [ 74 ], barrier reduction and tunnel current of 1: 75' 76 were also observed later in wide band gap cgse DEEP CYCLE BATTERY.The development status of Cu - In - Ga thin-film solar DEEP CYCLE BATTERY is shown in Practice .1.See [ 89 ] for more information on devices without CD buffer layers.
The research on copper indium gallium selenium DEEP CYCLE BATTERY with high conversion efficiency shows that if the defect density in vivo is further reduced, the conversion efficiency may exceed 20 %.However, it is also believed that due to the existence of the tail state, the best device performance has been achieved [ 77' 78 ].By observing photoluminescence, the tail state may contribute to carrier separation and collection of photogenerated current, but it has a great effect on shielding current and affects DEEP CYCLE BATTERY performance.On the other hand, even if the narrow band gap single junction DEEP CYCLE BATTERY has approached the limit of conversion efficiency, the stacked DEEP CYCLE BATTERY with wider band gap still has great potential to improve conversion efficiency ( see section 6.6.7 ).
Commercialization of Cu - Ga - Se Thin Film Solar Cells
Although the copper indium gallium selenium thin film solar cell module with high conversion efficiency was demonstrated several years ago and the early proof of concept [ 9 ] was achieved, the commercialization is still in the initial test line stage for a long time.Therefore, Cu - In - Ga - Se thin film solar DEEP CYCLE BATTERY are still not the mainstream products in the solar cell market.However, some industrial laboratories are carrying out relevant research and development directly, while more and more companies around the world are continuously developing commercial products of copper, indium, gallium and selenium thin film solar DEEP CYCLE BATTERY for power generation market and niche market.In 1998, Germany's Siemenssoularindustries announced the production of the first commercial copper indium gallium thin-film solar cell module with rated power of 5W and 10W. The test line is located in Camarillo, California, U.S. ( Currently, Germany's Avancisgmbh has taken over the Siemenssoularindustries copper indium gallium selenium thin-film solar cell business, while Camarillo's production line is run by Dutch Shell Solar ).At present, the major manufacturers of copper langga selenium thin film solar DEEP CYCLE BATTERY are shell solar and Germany wurth solar.Shell Solar upgraded the capacity and component size of Camarillo production line.Shell Solar's current full-size components have a power rating of 40W, while Wurth Solar's full-size components have a power rating of 80W and a size of 60cmx 120 cm.Shell Solar and Wurth Solar have published the yield data and conversion efficiency distribution of the production line, clearly demonstrating the feasibility of large-scale production of copper indium gallium selenium thin film solar DEEP CYCLE BATTERY.Wurth Solar has announced that a new plant with an annual capacity of 15 MWp / a will start operation in 2007 [ 91 ].
However, the commercialization of Cu - In - Ga - Se thin film solar DEEP CYCLE BATTERY from laboratory to mass production is more difficult than expected. The main obstacle is M:
Equipment on a commercial scale;
Quality control and in-situ monitoring;Uniformity;
The open circuit voltage is low;
Some process steps of Cu - In - Ga - Se thin-film solar DEEP CYCLE BATTERY require custom-made large-area deposition equipment, which is based on past experience in manufacturing laboratory-scale equipment, so commercial-scale equipment is costly and error - prone.As the number of installations increases, equipment manufacturers will gain more experience.The rapid commercialization of other thin film technologies is also very beneficial to increase equipment manufacturing experience.Manufacturers of glass can use the experience of large-area glass coating to produce glass substrates coated with diffusion barrier layers and Mo back electrodes.The sputtering coating machine for transparent conductive oxide TCO is similar to the equipment for preparing TCO for liquid crystal flat panel displays.Equipment manufacturers are actively participating in the preparation of the pilot line and expect to launch turnkey project with mature process and product parameters in the near future.
The basic research of Cu - In - Ga - Se thin-film solar DEEP CYCLE BATTERY has always ignored the GO - NO - GOTEST standard and the quality control method of in-situ monitoring after the process steps.However, with more and more laboratory research turning to mass production, quality control has made considerable progress in recent years.Raman spectroscopy [ 93 ] and photoluminescence luminescence decay [ 94 ] can detect the quality of the absorption layer.X - ray fluorescence ( x - ray 11110 561 6 ) [ 95 ] can measure the stoichiometric ratio of group vi elements to metal elements.Laser light scattering and substrate temperature monitoring have been discussed in section 6.3.1.
Uniformity and open circuit voltage va have been better improved in actual production.The copper indium gallium selenium thin film solar cell module has high conversion efficiency ( see actual .2 ).
The RTP process of rapid heat treatment has optimized the production rate of the process.Increasing the width of deposition can also increase the production rate of evaporation technology.Reducing the film thickness [ 96 ], optimizing the pattern scribing, removing the buffer layer [ 86 ] in the component structure and high-speed reactive TCO sputtering can further improve the production rate of large-scale production of copper indium gallium selenium thin film solar DEEP CYCLE BATTERY.
The increase of production scale of copper indium gallium selenium thin film solar cell increases the installation amount.However, more installation requires high stability of components.
The outdoor test proves that the component has good stability and the long-term stability has also been evaluated.In the accelerated aging test certified by IEC 61646, the wet heat test is a major challenge to the stability of copper indium gallium selenium thin film solar DEEP CYCLE BATTERY [ LEHL 2 ].However, the obvious degradation phenomenon in the stress testing process is temporary, and the conversion efficiency can be restored after several days of light aging treatment.The exact cause of degradation is still under study, but the empirically optimized components have been certified [ 6' 993 ].
In a word, many technical problems have been solved, but there are still some financial risks in the commercialization of copper indium gallium selenium thin film solar DEEP CYCLE BATTERY.Because of the lack of manufacturing experience of the relevant deposition equipment, the turnkey project cannot be realized yet, and the technology can only be developed step by step.Compared with the traditional crystalline silicon solar cell which has been put into mass production, the copper indium gallium selenium thin film solar cell needs to continue for a longer period of time in order to expand the production scale and thus reduce the production cost.Copper, indium, gallium and selenium thin-film solar DEEP CYCLE BATTERY are different from crystalline silicon solar DEEP CYCLE BATTERY in some inherent characteristics, which make them innovative products that meet the niche market and have higher market prices, which can bring rapid return on investment for small start-up companies. However, the medium and long-term profits still need to expand production scale, reduce costs and open up the electricity market.
Early cost analysis [ 1 3 ] predicted the production cost of 0.6 / WP for the copper indium gallium selenide thin film solar cell production line with an annual capacity of 60 MWp / a, while the production cost of 500 MWp / a for the cost-effective polysilicon technology to achieve similar production cost [ 1 4' 1 < ] 5 \ other cost analysis compared the direct component production cost of various solar DEEP CYCLE BATTERY such as monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride and copper indium gallium selenide, and estimated that the production cost of 10 MWp / a copper indium gallium selenide thin film solar cell production line can reach $ 2.25 / WPThe cost analysis is based on the average module conversion efficiency of 9 % and the yield of 65 % for copper indium gallium selenium thin film solar DEEP CYCLE BATTERY, while the conversion efficiency and yield of the test line are obviously higher today.According to the first generation on-line process estimation, a 100 MWP / A production line with optimized conversion efficiency and yield can reduce the production cost to $ 1 / WP, which is 15 % lower than polysilicon technology.The latest cost analysis shows that the CUI NSA test line of 5 MWP / A can realize the cost of 1.5 / WP and the performance of 6.5.2 components. We already know that the copper indium gallium selenium thin film solar cell has high conversion efficiency development potential.Since the non-uniformity of monolithic integration and large-area fabrication does not cause excessive losses, small components and full-size components can also have higher conversion efficiency ( see actual .2 ).
For large-scale production, the distribution of conversion efficiency ( or output power ) is more important than that of monolithic components.WiirthSolar of Germany reported the output power of a batch of 306 60 cmx 120 cm assemblies 79.9 2.2 WP, indicating that a narrow output power distribution curve can be achieved.In 2004, the yield of Wurth Solar was > 80 %, and the average component conversion efficiency was slightly higher than 11 % [ 109 ].According to a report by Dutch Shell Solar in 2002 [ 11 ], nearly 16000 pieces of modules laminated in Camarillo by 1x4 have an average conversion efficiency of 10.9 %.
The rated power output is the most important performance parameter for solar cell applications.The components not only need to be applied under standard test conditions STC for testing rated power, but also need to show good performance under actual operating conditions.Under practical operating conditions such as low light intensity, nonstandard spectral distribution, local shading and high temperature environment, the copper indium gallium selenium thin film solar cell shows high output power and KWH / KWP performance ratio.The optimized shunt resistance improves the performance under low light intensity, the narrower interconnection area reduces the influence of local shadows, and the wider band gap limits the loss of component temperature increase [ 1 degree ].Therefore, the KWH / KWP performance ratio of copper indium gallium selenide thin film solar DEEP CYCLE BATTERY is better than that of crystalline silicon solar DEEP CYCLE BATTERY [ 99,109,in ].
The sustainability of copper indium gallium selenium thin film solar DEEP CYCLE BATTERY has many aspects.Although not all the issues have been clarified, the relevant data are ideal.Due to high conversion efficiency, good KWH / KWP performance ratio, long service life, low consumption of raw materials and low thermal budget, copper indium gallium selenium thin film solar DEEP CYCLE BATTERY have good energy balance o many studies [ 112 ] have described the sustainability of their large-scale production.Like many large-scale industrial production, the commercial production of copper, indium, gallium and selenium thin-film solar DEEP CYCLE BATTERY may also have problems related to waste recovery, energy consumption and shortage of raw materials.Sustainability forces waste to be recycled before the end of production and components to be recycled before the end of their useful lives.According to the European law on electronic products, manufacturers should also take back the component ⑽ under certain circumstances.
Supply and recycling of raw materials
Thin film solar cell technology can use raw materials very effectively.The traditional crystalline silicon solar cell module requires 0.51 kg / m2 of semiconductor grade silicon, while the raw material consumption per m2 of CISE cell module is: mo 720 g, cul.54g, in39g, se 720 g, znl3g ( depending on the module structure and yield [ | 14 ] ).This means that the consumption of raw materials is only equivalent to the metallized grid lines of crystalline silicon solar DEEP CYCLE BATTERY.
Whether the shortage of In will become the bottleneck of the development of Cu - In - Ga - Se thin film solar DEEP CYCLE BATTERY has become a controversial topic.2003.In is mainly used in coating ( 65 % ), electronic components ( 10 % ), solders and alloys ( 15 % ) [ 115 ].In - based coating is applied to the production of ITO transparent contact electrodes for flat panel displays.The annual production of in worldwide is 300 t, mainly from zinc ore, and 300 t in can produce about 15 GWP / a copper indium gallium selenium thin film solar cell module.On the other hand, in reserves in the earth's crust are three times that of ag, while ag's annual output is 20000 t and its reserves are 57000 t [ 115 ].These figures mean that the supply of In cannot be a limiting factor in the commercialization of Cu - In - Ga - Se thin film solar DEEP CYCLE BATTERY.In addition, the research shows that thinner absorption layer is a feasible technical direction [ 116 ], and no - in absorption layer is also under development ( see section 6.6.3 ). moreover, the flat panel display industry may replace ITO with cheaper ZnO, and in recovery will supplement in supply, which will reduce the risk of in supply shortage.In the past 30 years, the price of in has fluctuated between < $ 100 / kg and > $ 500 / kg, while the market price of $ 500 / kg means in accounts for only 2 % of the production cost of components.
The waste produced by the dry process is mainly the residual material deposited on the side wall of the cavity, baffle or substrate carrier, etc.The total amount of waste in the small-scale test line is small and the recovery cost is high. It is hoped that the waste recovery cost can be reduced in the large-scale production.The remaining sputtering target produced will be recovered by the supplier.More research has focused on the recovery of waste materials from buffer chemical water bath deposition CBD [ 117, 118 ]. The main method is to remove reaction products from the solution at the production site, adjust the concentration of the solution, and then re-apply the solution to CBD.
After successful testing, the final product of disassembly and recovery of defective products or semi-finished products can be applied to end - of - life products.Add G to 250' C to the components to be disassembled, soften the EVA packaging film, and then remove the cover glass.After that, the window layer and buffer layer are removed by etching with weak acid solution.Then scrape off the absorbent layer from the back contact, and finally dissolve the back contact in HN03'. The test shows that this assembly can be disassembled layer by layer with little cross contamination.It has been confirmed that the substrate glass can be reused in the new assembly, and it is hoped that relatively clean materials such as the absorption layer powder can also be directly used in the subsequent preparation process' 18.104.22.168 Energy Recovery Period'
A manufacturer producing both copper indium gallium selenide thin-film solar DEEP CYCLE BATTERY and crystalline silicon solar DEEP CYCLE BATTERY gave a comparative study of the energy recovery period [ 12 ] and believed that the energy recovery period EPBT of copper indium gallium selenide thin-film solar DEEP CYCLE BATTERY was 1.8 years, while that of crystalline silicon solar DEEP CYCLE BATTERY was 3.3 years.It is worth noting that the aluminum frame accounts for a large proportion of the energy value of copper indium gallium hitting the thin film solar cell module material.However, this study is based on the first generation of copper indium gallium smashing thin-film solar cell technology, and the energy recovery period EPBT will be lower in the future.
Development of Cu - Ga - Se Thin Film Solar Cells
Copper indium gallium smashing thin-film solar DEEP CYCLE BATTERY is still the focus of international research and development of thin-film solar cell technology.The results of basic theoretical research and preparation technology development will further enhance the market potential, module performance and sustainability of copper indium gallium selenium thin film solar DEEP CYCLE BATTERY, and make the next generation of solar DEEP CYCLE BATTERY realize maximum economic and social benefits in large-scale production.We will summarize the relevant research and development directions in the following paragraphs.
Flexible solar cell
If the rigid glass substrate is replaced by a light-weight flexible substrate, the copper indium gallium selenium thin film solar cell can be made into a flexible solar cell [ 26 ], which will open up a new market segment O in addition.Flexible solar DEEP CYCLE BATTERY can be prepared by roll-to-roll process, which will effectively reduce the production cost [ 1 8 ].The flexible substrate may be a plastic sheet or a metal sheet.Copper - indium - gallium - selenium flexible solar cell has light weight, good radiation resistance and high conversion efficiency ( compared with other thin film solar cell technologies ). It is very suitable for space photovoltaic applications. The substrate temperature of copper - indium - gallium - smashed thin film solar cell is too high for ordinary plastic sheets, which will cause shrinkage, curling, gasification and hardening problems. Reducing the substrate temperature will reduce the conversion efficiency.Polyimide achieved the conversion efficiency record of < 15 % for copper indium gallium selenium flexible solar cell on plastic sheet substrate [ 83 ].
On the other hand, as a flexible substrate, the metal foil needs to avoid pinhole defects.Change the interconnection mode of monolithic integration to ensure conductivity.Metal elements in the metal sheet substrate will diffuse into the absorption layer, forming pinhole defects and changing material properties.The diffusion barrier layer being researched and developed can play the role of substrate isolation and improve the performance of the device.The copper, indium, grain and selenium flexible solar DEEP CYCLE BATTERY on thin metal substrates often adopt tile-like integration instead of monolithic integration.
Since soda-lime glass is no longer used as a rigid substrate, various flexible substrates need sodium doping, such as precursor film, co-evaporation or diffusion after the absorption layer is prepared.
cadmium - free buffer layer
Although the very thin CdS buffer layer will not cause substantial pollution to the environment, CD is still a theoretical toxic substance, and the cadmium-free buffer layer will make the copper indium gallium selenium thin film solar cell module more acceptable to the market and can further reduce the cost ( avoiding expensive safety measures ).According to EU regulation [ 122 ], since July 2006, the electrical and electronic equipment sold will not contain several heavy metals such as CD.Although solar cell modules are not yet covered by relevant laws and regulations [ 113 ], cadmium-free buffer layer is still the focus of current research and development.We will selectively introduce several kinds of buffer layer technologies that can replace CD.More information can be found in the commentary [ 89 ].
Wet chemical process
As a wet chemical process, the buffer layer prepared by chemical water bath deposition of CBD is not limited to CDs, but also sulfide, oxide, hydroxide and mixtures thereof of in or Zn can be used.These cadmium-free buffer layers can even achieve a conversion efficiency similar to that of standard devices [ 84 ].Because the deposition parameters are sensitive and the requirements for the absorption layer are high, the reproducibility of the performance of the cadmium-free buffer layer device is not high.After photoaging treatment, the performance of cadmium-free DEEP CYCLE BATTERY will be significantly improved, showing metastable effect [ 123 ].At present, the impact of cadmium-free buffer layer prepared by CBD on long-term stability is not clear.At present, only one test line uses Zn - based buffer layer ( see actual .2 ).
Ionization Layer Gas Reaction ( IL GAR ) is another new wet chemical process, mainly applied to cadmium-free buffer layer [ 124 ].The results show that ZnO deposited by IL GAR not only has the function of cadmium-free buffer layer, but also has the function of undoped window layer ( usually prepared by sputtering ) [ 125 ].
Although wet chemical process is the lowest cost deposition technology, in typical process, only the buffer layer is deposited using wet chemical process, which is not conducive to on-line operation.Since the deposition systems are not connected to each other and the scribing is also carried out in the air, independent wet chemical processes are not a big problem in the test line, but may cause inconvenience in future large-scale production.Therefore, people began to consider the feasibility of dry process, especially MOCVD CW and atomic layer chemical vapor deposition ( A LCVD ) [ 127 ].MOCVD deposited devices have good conversion efficiency, but so far only small samples have been deposited.Atomic layer chemical vapor deposition ( ALCVD ) A LCVD can produce 30 cm x 30cm DEEP CYCLE BATTERY of medium size, but the process is slow. Only by depositing many substrates at the same time can a certain cost benefit be realized and can not meet the requirements of on-line operation.
If the absorption layer is prepared by evaporation, the buffer layer is also prepared by evaporation and is particularly suitable for in-line mass production [ 128 ].After the absorption layer is deposited, the buffer layer can be evaporated in situ without leaving the vacuum environment, and the conversion efficiency of nearly 15 % has now been achieved [ 8.
Compared with chemical water bath deposition of CBD, evaporation, MOCVD and A LCVD are all " soft" deposits, which is a unique advantage.If sputtering can also prepare cadmium-free buffer layer, it will be a good technical route.Sputtering is not soft deposition. It is presumed that one of the main functions of the buffer layer is to protect the surface of the absorbing layer and avoid the damage of sputtering to the surface of the absorbing layer when depositing the window layer.Some experimental results also support this view. When the buffer layer is ignored and the transparent conductive oxide TCO is directly sputtered on the absorption layer, the device performance is poor.The surface of the absorbing layer can be stabilized during the sputtering process of the window layer by preparing a thin film on the absorbing layer with a certain chemical treatment with electrolyte [ 129 ].Without chemical treatment, sputtering in, s buffer layer can also achieve a conversion efficiency of > 12 %.
Another novel technique of non - blessing buffer layer is to consider changing the structure of heterojunction and modifying the window layer so that buffer layer is no longer needed.Since the band structure of the CIGSE / TCO heterojunction will cause poor device performance, experiments show that ( Zn, Mg ) O can be used instead of undoped ZnO as the layer contacting the absorption layer in the two-layer TCO film to optimize matching.Kelvin force microscope KPFM's measurement of the cross-sectional work function of solar DEEP CYCLE BATTERY supports such a theoretical model … 1.The concept of DEEP CYCLE BATTERY conversion efficiency of 12.5 % proves the feasibility of the ( Zn, Mg ) O structure [ 1 gas needs further research and development to achieve long-term stability of device performance and reproducibility in the test line.The ( Zn, Mg ) O alloy can be deposited by sputtering with a single mixed boot material, and its conductivity is close to the standard undoped ZnO.Therefore, sputtering ( Zn, Mg ) O can directly replace CBD and be conveniently integrated into the existing test line process to prepare standard components.
Indium - free absorption layer
Some people think that the shortage of In will restrict the large-scale production of Cu - In - Ga - Se thin-film solar DEEP CYCLE BATTERY ( see 22.214.171.124 Festival ), which leads to the study of indium - free absorption layer.The Cu 2 ZnSn ( S, Se ) UT compound with the crystal structure of zinc yellow tin ore can be obtained by replacing half of the in atom of chalcopyrite crystal structure with Zn atom and the other half of the in atom with Sn atom.The mature process for preparing chalcopyrite structure can also prepare Cu 2 ZnSn ( S, Se ) 4T 132' 133, and can form heterojunctions with conventional Mo back contact and CdS buffer layer.However, the binary phase Cu. se problem of zinc yellow tin ore crystal structure is more serious than chalcopyrite structure, so far only 5 % conversion efficiency has been achieved, and no indium absorption layer needs further research and development.6.6.4 Novel Back Contact Mo is the most widely used back contact material in the current structure and preparation method of copper indium gallium impact thin film solar DEEP CYCLE BATTERY.However, Mo's decay candle [ 135 ] will cause degradation of components in accelerated aging tests.If Mo alloy is used instead of pure Mo, the stability of the assembly can be increased.Another disadvantage of Mo is poor light reflection, which is not conducive to further reducing the thickness of the absorption layer.Whether it can maintain stability under the conditions of absorbing layer deposition limits the choice of other metal materials.W can achieve good ohmic contact but poor light reflection.Ta and Nb have better light reflection and show better contact electrode characteristics [ 136 ].The metal contact coated with transparent conductive oxide TCO is another feasible design with good stability, electrical properties and optical properties.Double - sided configuration also requires a good TCO / CIGSE ohmic contact.
Double - sided configuration and upper-layer configuration
The double-sided configuration replaces opaque metal back contact with transparent conductive oxide TCCP 373 and has unique application advantages.At the present stage of development, the conversion efficiency of light transmission into back-to-back contact is low.The generation of photogenerated carriers is far away from the space charge region where the electric field is strongest and close to the back contact where the blue light response is poor and passivation is not ideal.Therefore, the double-sided configuration needs to further optimize the thickness of the absorption layer, diffusion length and passivation of the contact electrode.
In the traditional substrate configuration, opaque back contact is deposited on the glass substrate and encapsulated with another piece of glass to become a transparent front surface to receive incident light.In principle, it is also possible to start deposition on transparent front contacts to form an upper layer configuration, with light entering the DEEP CYCLE BATTERY only from the front surface.Because the area of TiO _ 2 / CIGSE interface is very large, a smaller interface recombination speed is required, but now it is found that heterojunctions or buffer layers are beneficial to achieve better interface characteristics [ 143 ].
Non - vacuum process
The non-vacuum process under research and development can reduce the upfront investment required for some process steps, thus reducing the entry threshold and financial risk for large-scale production of copper indium gallium selenium thin film solar DEEP CYCLE BATTERY, but it may not be able to reduce the overall production cost.Due to the mixed use of vacuum equipment and non-vacuum equipment, the corresponding infrastructure requirements are higher, the wet chemical process produces more waste, and the operation cost will even be higher.Mo back contact cannot be prepared by a non-vacuum process. Chemical water bath deposition CBD and MOCVD for preparing buffer layer and window layer respectively are non-vacuum processes. Metallized glass may be purchased directly from glass manufacturers without on-site preparation.The non-vacuum process of the absorption layer is usually based on the process ( see 126.96.36.199 Section ), which requires the precursor layer deposited at room temperature to anneal at high temperature and undergo a certain chemical reaction.In the second step of the process, selenization is already a relatively mature non-vacuum process in the environment where H2Se and inert carrier gas are mixed.The copper, indium, gallium and selenium thin-film solar cell prepared in the early stage will use the metal precursor of the absorption layer deposited by electroplating [ 1453 ], and now the research and development has made new progress [ 146 ], realizing medium laboratory conversion efficiency.The non-vacuum process based on the electroplating of metal / Se precursors has been participated by some enterprises, achieving a conversion efficiency of 10 % for small-area batteries [ 147 ].Other research groups have achieved higher conversion efficiency with Se - containing precursors, but the precursors still need to be pre-treated with traditional evaporation techniques [ 148 ].
In addition to electroplating, the non-vacuum process can also use ink or slurry for spraying or spraying, printing, dip coating or scraping to prepare the absorption layer.In one process [ 149 ], metal is dissolved in acid and hydroxide nanoparticles are precipitated from the solution.After dewatering the nanoparticles, fine powders of mixed oxides are obtained.Then, the fine powder is diffused into the aqueous solution to form an ink in a colloidal state.In such a non-vacuum process, the relative concentrations of various nanoparticles can be conveniently adjusted to accurately control the composition of the film.Oxide nanoparticles as precursors also require an additional reduction reaction and then selenization in a diluted H2 atmosphere.The precursor film can also be prepared into porous nanostructures [ 15 ].In principle, precursor nanoparticles can be made to contain Se or S by sintering without chemical reaction, but the device performance of this non-vacuum process is not ideal.
Wide band gap DEEP CYCLE BATTERY and laminated DEEP CYCLE BATTERY
Wideband gap batteries can not only produce better performance single junction batteries, but also form $ batteries for stacked batteries.If the band gap of a single junction DEEP CYCLE BATTERY is increased to about 1.4 eV, the conversion efficiency will approach the theoretical maximum of the band gap / conversion efficiency relationship [ 1 ( 1 ) ].Since the current density of the wide band gap DEEP CYCLE BATTERY is reduced, the transparent conductive oxide TCO can be allowed to have a higher resistance.Moreover, since the maximum wavelength absorbed by the wide band gap DEEP CYCLE BATTERY is smaller than the wavelength at which free carrier recombination occurs in TCO, the doping concentration of TCO can be increased within a certain range.Therefore, the reduction of TCO thickness can reduce the cost' compared with narrow-band gap batteries, the performance loss of wide-band gap batteries at high temperature is smaller, and the KWH / KWP performance ratio of annual power output is better ( especially in hot weather ).The theoretical conversion efficiency limit of stacked DEEP CYCLE BATTERY is even higher than that of crystalline silicon solar DEEP CYCLE BATTERY.U.S. National Renewable Energy Laboratory NREL CIGSE Narrow Band Gap Battery ( EGL. 1EV ) can achieve a high conversion efficiency of 19.5 % and is an ideal bottom DEEP CYCLE BATTERY, while the more appropriate top DEEP CYCLE BATTERY band gap should be 1.7 eV [ 15A, the front contact and back contact of the top DEEP CYCLE BATTERY should be transparent.
Ideally, the top cell can be deposited directly on the bottom cell to form a monolithic stacked cell.
Up to now, there is no broadband gap DEEP CYCLE BATTERY with high conversion efficiency, which has some historical reasons.On the other hand, there are significant differences between the theoretical calculation prediction [ 153 ] and the experimental data confirmation for various parameters that determine the DEEP CYCLE BATTERY conversion efficiency, and it is still difficult to judge how to recognize and solve such differences.As the focus of international basic research, these problems of wide band gap DEEP CYCLE BATTERY and laminated DEEP CYCLE BATTERY may be solved in the near future.Related literature describes samples of monolithic stacked DEEP CYCLE BATTERY [ 155 ] and mechanically stacked stacked stacked DEEP CYCLE BATTERY [ 15 ].In order to improve the conversion efficiency of Cu - In - Ga solar stack DEEP CYCLE BATTERY, amorphous silicon or CdT W15 has been proposed as the top cell.
An introduction to
The development of cadmium telluride thin-film solar DEEP CYCLE BATTERY has gone through a long process. In 1972 Bonnet and Rabin Horst attracted CDS / CdTe solar DEEP CYCLE BATTERY W with a conversion efficiency of 6 %, while in 2002 NREL researchers in the US National Renewable Energy Laboratory achieved a laboratory conversion efficiency record M of 16.5 %.In the past 30 years, our understanding of the physical nature and operation principle of cadmium telluride thin film solar DEEP CYCLE BATTERY has been increasing, and we have also accumulated more experience in their deposition methods and preparation processes.At present, there are two famous manufacturers of cadmium telluride thin-film solar DEEP CYCLE BATTERY in the world, Germany's ANTECSOLERGFW and America's First Solar 0, often have comments on the research progress of cadmium telluride thin-film solar DEEP CYCLE BATTERY [ 7 - 11 ], and some people have recently summarized the development history of cadmium telluride thin-film solar DEEP CYCLE BATTERY [ 12 ].In this chapter, we will introduce the process and characteristics of cadmium telluride thin film solar DEEP CYCLE BATTERY, and focus on the discussion from the perspective of physical characteristics and numerical modeling.
At present, crystalline silicon solar DEEP CYCLE BATTERY are still the leading technology in photovoltaic industry.If high performance is considered, no other technology can replace monocrystalline silicon or polycrystalline silicon solar cell components.However, in order to make photovoltaic power generation an important form of energy in various countries, solar DEEP CYCLE BATTERY need to greatly increase production and greatly reduce costs.Considering material utilization, mass production and component integration, thin-film solar DEEP CYCLE BATTERY have fundamental advantages over crystalline silicon solar DEEP CYCLE BATTERY, which have been the driving force for research and development of thin-film solar DEEP CYCLE BATTERY since the 1960s.Of all the studied thin film solar cell materials and processes, three materials stand out to the level of technical maturity and have already started commercial production:
Cadmium hoofed thin film solar cell:
Copper indium gallium selenium thin film solar cell:
Silicon - based thin film solar DEEP CYCLE BATTERY based on a - si: h, MC - si, a - sige: h, a - sic: h
Other DEEP CYCLE BATTERY materials and technologies have also developed rapidly, especially crystalline silicon thin film solar DEEP CYCLE BATTERY and various nanostructured solar DEEP CYCLE BATTERY, such as dye-sensitized solar DEEP CYCLE BATTERY and organic solar DEEP CYCLE BATTERY.
CdTe materials are particularly suitable for preparing thin film solar DEEP CYCLE BATTERY [ 1, 13 ], with a direct band gap of 1.45 eV and within the optimum band gap range of 1.2 - 1.5 eV for photovoltaic conversion [ W - 18 ].Crystal silicon and CUI NSE2 are at the lower end of the optimal band gap range.Cu ( in, ga ) se2, CdTe, Cui nsz and GaAs have the best band gap?Cug ase 2 and A _ Si: H are at the upper end of the optimum band gap range.Since the absorption coefficient of CdTe is higher than A - Si: H, and the CdTe' several - thick' than crystalline silicon is enough to absorb all human sunlight, the minority carrier diffusion length of the order of magnitude is enough to allow almost all photo-generated carriers to be collected by the contact electrode, which can greatly reduce the requirement on material quality, and the CdTe polycrystalline layer of the order of magnitude grain size can meet the design requirements.Even without passivation process steps, the grain boundary electrical activity of other N - VI polycrystalline layers such as CdTe and Cu ( In, Ga ) Se2 is low, which is a good physical property.
CdTe is the only stable CD - Te compound in the CD - Te phase diagram, and the superior property of solid-liquid co-component melting O allows a variety of deposition techniques to prepare CdTe thin films of near stoichiometric device quality.On the other hand, CdTe, unlike Cu ( In, Ga ) Se2 or A - SiGe: H, A - SiC: H, can design the band gap distribution in the device.The high energy of CD - Te and CD - S chemical bonds, the extremely low solubility of CdTe and CdS compounds in water and the low air pressure of these components are all advantages in environmental protection.
Other material properties will reduce the advantages of cadmium telluride thin film solar DEEP CYCLE BATTERY.CdTe as a binary compound has many inherent defects, which makes it difficult to accurately control the doping concentration.Inherent defects and foreign elements can stimulate the self-compensation reaction, which increases the difficulty of doping CdTe impurities.The problem of inherent defects in CdTe is much more serious than that of Cu ( In, Ga ) Se2.It is difficult to realize high-concentration P - type doping in CdTe thin films, which is an obvious disadvantage of the material.Activation treatment and novel contact electrode design are potential methods to solve the inherent defects of CdTe, and have become the main research topic of CdTe thin film solar DEEP CYCLE BATTERY.
This chapter will introduce cadmium telluride thin film solar DEEP CYCLE BATTERY from several aspects:
Preparation process of batteries and components:
Physical properties and numerical modeling.
Broken' 4 still
Because the deposition temperature or annealing temperature is relatively high ( > 400 c ) in most cadmium telluride thin film solar cell technologies, the interaction between the CdTe absorbing layer and other cell materials ( substrate, window layer, buffer layer and contact electrode ) is inevitable.There are two kinds of so-called material properties:
The measured material properties in a separate CdTe layer on an inert substrate may not be suitable for describing CdS / CdTe solar DEEP CYCLE BATTERY;It is difficult to measure the properties of CdTe materials in a complete DEEP CYCLE BATTERY. Other layers will affect the standard methods of measuring properties and even make them completely ineffective.
We will discuss several characteristics of cadmium telluride thin film solar cell materials.For the above reasons, the relevant values can only reach the accuracy of the order of magnitude.
The direct bandgap transition has a direct bandgap field of 1.487 eV.DEEP-CYCLE BATTERIES
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