Thin-film Modules Research Articles

Impact of Shunt Resistance on the Performance of Curved Thin-Film Photovoltaic Modules With Series-Connected Solar Cells

Curved photovoltaics (PV) is gaining widespread application in modern energy-efficient infrastructure, wearable electronics, and vehicles. Due to the different orientations of the solar cells in curved PV modules, current mismatch between solar cells is more prevalent in curved PV than conventional flat PV. In this article, we investigated the effect of shunt resistances, which can mitigate current mismatches in series-connected solar cells, on the performance of curved thin-film PV modules. A flexible 85 × 80 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Cu(In,Ga)Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mini-module composed of 17 series-connected solar cells on a curved surface was characterized experimentally and theoretically. We found that the short-circuit current of the curved PV module is affected by all the solar cells connected in series and is not simply determined by the current-limiting solar cell. The current-voltage characteristics of a curved PV module are well described by a simple model that includes low shunt resistance. The power generated from normal irradiance decreases with shunt resistance; however, the power for tilted illumination is higher than that of a module without shunt resistance. This indicates that the low shunt resistance can suppress the power loss due to current mismatch. In addition, curved PV modules cause self-shading under highly tilted illumination but curved PV modules with low shunt resistances provide power even when some solar cells are not illuminated. Furthermore, sudden current mismatches in solar cells, which generate detrimentally high reverse biases can be eliminated by the shunt resistance. This confirms the protective effect of the shunt resistance to enhance the durability of curved PV modules.

Life Cycle Analysis of Thin-Film Photovoltaic Thermal Systems for Different Tropical Regions

Different energy solutions are required to satisfy the energy demand of the world’s ever-growing population. Photovoltaic Thermal systems (PVT) could propose resolutions to tackle real-time issues regarding power generation. Life Cycle Analysis (LCA) is performed to compare the environmental impact and measure the energy across different PVT modules consisting of a-Si, CdTe, and CIS thin-film solar cells. The authors performed LCA to calculate the energy payback time (EPBT) and life-cycle CO2 emissions of residential rooftop and open-field PVT systems. The primary energy needed to produce thin-film PVT modules of 1 m2 cell area was considered in the present life cycle analysis studies operated using water as the working fluid. The annual net electrical energy savings at various Indian weather conditions, such as New Delhi, Jodhpur, and Ladakh, have been calculated. For the thin-film PVT systems, the calculated values of annual energy yield for three locations with average solar radiation levels and peak sun hours in the range of 600–1000 W/m2 and 6–8 h were reported. Results show that the CO2 emissions for rooftop installation of CdTe and CIS are around 200 and 156 kg/annually, which is lower than the open field installation of the same, where CO2 emissions were found to be 295 and 250 kg/year.

CURRENT STATE OF SOLAR PHOTOVOLTAIC PANELS WASTE MANAGEMENT OPERATIONS IN UKRAINE

The paper analyzes the steady trend of solar energy development, which is accompanied by the formation and accumulation of solar panel waste. This process requires the application of accomplished waste management and the development of waste disposal technologies. It was determined that the problem of waste solar photovoltaic panels becomes more urgent due to the military actions taking place on the territory of Ukraine. The general characteristics of waste for different types of panels are given. The heterogeneity of the materials of photovoltaic panels leads to an ambiguous classification and involves a combination of safe and dangerous components. It has been determined that photovoltaic panel waste can be divided into two hazard classes: hazardous waste and non-hazardous waste. The key points of solar panel waste management operations are characterized in accordance with the Law of Ukraine “On Waste Management” and EU Legislation. The main points of disposal of unusable photovoltaic panels with recovery of valuable raw materials are described. It is noted that there are significant differences in the material composition of crystalline silicon panels and thin film modules. It is noted that two processing types of PV modules are currently distinguished – coarse and fine, and the most effective steps in the preparatory stage of disposal are also determined. In general, PV panel waste disposal operations combine mechanical and chemical material extraction processes. The imperfection of the legislative and regulatory framework in the field of waste management, the increase in the ecological danger of the generation and accumulation of waste, the imperfection of the information base and waste monitoring, the insufficient development of the processes of organizing the processes of collection, accumulation and transfer of waste for disposal, the insufficiency of proposals for methods of processing and disposal of solar panels waste as a valuable resource of secondary raw materials are notable as the main problems in the field of waste management of photovoltaic panels in Ukraine. One of the main tasks for development is to increase the share of waste materials that are currently not disposed of, but can be used as secondary raw materials.

Physics-based electrical modelling of CIGS thin-film photovoltaic modules for system-level energy yield simulations

Copper indium gallium selenide (CIGS) is a commercialized, high-efficiency thin-film photovoltaic (PV) technology. The state-of-the-art energy yield models for this technology have a significant normalized root mean square error (nRMSE) on power estimation: De Soto model—26.7%; PVsyst model—12%. In this work, we propose a physics-based electrical model for CIGS technology which can be used for system-level energy yield simulations by people across the PV value chain. The model was developed by considering models of significant electrical current pathways from literature and adapting it for the system-level simulation. We improved it further by incorporating temperature and irradiance dependence of parameters through characterisation at various operating conditions. We also devised a module level, non-destructive characterization strategy based on readily available measurement equipment to obtain the model parameters. The model was validated using the measurements from multiple commercial modules and has a significantly lower power estimation nRMSE of 1.2%.

Flexible fabric-based GaAs thin-film solar cell for wearable energy harvesting applications

GaAs photovoltaic (PV) cells have been extensively studied for flexible energy harvesting devices due to their merits such as thin-film feasibility, flexibility, and high-efficiency. However, GaAs-based thin-film PV cells have a limitation for the applications in wearable platform since they are not compatible with fabric carrier. To handle this problem, we report thin-film transfer technique that involves a sacrificial layer with a double-layer structure, an Au–Au bonding technique, a Cr/Au bilayer to induce metal stress, and an etchant for fast epitaxial lift-off (ELO). In addition, a polyimide layer attached underneath the fabric substrate not only protects the fragile epi layer but also accelerates the lateral etching via spontaneous bending. The application of these techniques enables the successful transfer of GaAs thin-film PV epi structures onto fabric platform without degrading crystal quality. Fabric-based GaAs PV cells are fabricated via the standard PV cell fabrication process. The platform expansion of GaAs thin-film techniques has great potential for large-scale commercialization. • III-V epi-layers onto fabric substrate can be realized without degrading crystal quality. • The GaAs solar cells are directly integrated with fabric platform. • High efficiencies over 17.49% can be achieved on fabric platform. • Fabric-based GaAs solar cells present the stable output power with high flexibility.

Impacts on insulation resistance of thin film modules: A case study of a flooding of a photovoltaic power plant in Thailand.

Effects of high humid weather conditions on photovoltaic (PV) modules were examined in this study, particularly insulation resistance. Three types of tests were conducted which include leakage voltage test, leakage current test, and wet leakage current test. Due to the usual field constraints in the study of insulation resistance, which limited measurements of leakage current, assurance was made that representative sampling were conducted. The study found a high number of modules with low insulation resistance and high leakage voltage values, which can interrupt the PV plant operation. High leakage voltage creates safety hazards issues. About two third of the samples, which showed deep moisture ingress in the modules, could not pass the minimum criterion of IEC 61646 standard for wet insulation resistance testing. The leakage current results showed the same trend as of leakage voltage, proving that leakage voltage test, which is quite easy and economical, can be used to detect such type of problems in field tests. Prolonged humidity conditions of the PV power plant particularly from natural disaster, should be avoided. Efficient drainage system should be supported in and around installations and all other moisture sources should be regularly removed from the plant area to keep proper operation and minimize losses in energy production.

Electrical parameters behaviour evaluation of Copper Indium Gallium Diselenide thin-film photovoltaic modules

ABSTRACT This paper aims to study the metastability as well as the degradation of Copper Indium Gallium Diselenide (CIGS) thin-film photovoltaic modules. Potential-induced degradation (PID) test has been carried out on a CIGS thin-film module inside a climatic chamber with a high temperature (85°C), and relative humidity (85%). A negative voltage of −1000 V was applied to the active cell circuit with different configurations. Results showed that the GIGS thin-film module experienced drastically degradation, mostly for front and back contact configurations because of the large area of applying the negative voltage. The I-V curve showed losses in electrical parameters of the degraded module mainly in the maximum power and the fill factor (FF). Different changes in performance have been observed in the first hour of the test confirming that the tested modules exhibited metastability with the light soaking (LS) effect by improvement in open-circuit voltage (Voc) and FF. A recovery process has been performed on degraded modules by applying positive voltage of +1000 V, the losses in electrical parameters have been partially recovered to the initial value, this process confirms the effect of a high voltage on modules in PV system.

Enhanced Performance of Ternary CuGaSe 2 Thin‐Film Photovoltaic Solar Cells and Photoelectrochemical Water Splitting Hydrogen Evolution with Modified p–n Heterointerfaces (Adv. Mater. Interfaces 25/2022)

Efficient Photovoltaic Solar Cell and Hydrogen Evolution Using CuGaSe2-based Photoabsorber Layers In article number 2201266, Shogo Ishizuka, Riku Okamoto, Shigeru Ikeda, and co-workers develop an interface modification technique using Cu-deficient phases, alkali-metal doping, and an n-type buffer material for enhancing performance of CuGaSe2 thin-film photovoltaic solar cells and photoelectrochemical water splitting hydrogen evolution.

Irradiation-dependent topology optimization of metallization grid patterns and variation of contact layer thickness used for latitude-based yield gain of thin-film solar modules

We show that the concept of topology optimization for metallization grid patterns of thin-film solar devices can be applied to monolithically integrated solar cells. Different irradiation intensities favor different topological grid designs as well as a different thickness of the transparent conductive oxide (TCO) layer. For standard laboratory efficiency determination, an irradiation power of 1000,mathrm {W/m}^2 is generally applied. However, this power rarely occurs for real-world solar modules operating at mid-latitude locations. Therefore, contact layer thicknesses and also lateral grid patterns should be optimized for lower irradiation intensities. This results in material production savings for the grid and TCO layer of up to 50 % and simultaneously a significant gain in yield of over 1,% for regions with a low annual mean irradiation.Graphical

Significant improvement of conversion efficiency by passivation of low-angle grain boundaries in flexible low-cost single-crystal-like GaAs thin-film solar cells directly deposited on metal tape

We develop an easily implementable yet effective process to achieve high power conversion efficiency in newly-developed flexible single-crystal-like GaAs thin-film photovoltaic solar cells on cheap metal tape. We study various techniques on the fabricated devices to passivate the defect states associated with dangling bonds at low-angle grain boundaries (LA-GBs) existing in the single-crystal-like GaAs material. We report that sulfur by trioctylphosphine sulfide (TOP:S) solution treatment can partially but effectively passivate the defect states at the LA-GBs to increase all the solar cell performance parameters of open-circuit voltage VOC (33.2%), short-circuit current JSC (19.5%), and fill factor FF (25.8%), resulting in the improvement of the power conversion efficiency more than double. The material and device characterizations and numerical modeling are performed to propose a mechanism, also suggesting that the power conversion efficiency higher than 20%, which is an important target milestone in emerging solar cell technologies, can be achieved. This work presents the first effective passivation of the bulk defects in GaAs at the device level and can also offer a solution for other photonic and electronic devices using non-single-crystalline GaAs films for flexible electronics.

Development of a P1-filling process to increase the cell performance in the copper indium gallium Selenide photovoltaics by implementation of the inkjet technology

In this paper, the suitability of integrating a digital manufacturing tool i.e. inkjet technology is exemplified to increase the electrical performance of thin-film based Copper Indium Gallium Selenide (CIGS) photovoltaic (PV) modules. Typically, the series connection within the PV module is established conventionally by three adjacent scribing lines at different deposition stages (patterning P1, P2 and P3). The total width of these three scribes is typically in the order of several 100's of microns and is electrically inactive, so these regions are lost areas for current generation (up to 5% “dead area”). To reduce the line width of the first scribe (P1) without compromising on the electrical parameters, we have concentrated on accurately filling of the interconnect P1-trenches with insulating material using inkjet technology, as initial step to realize the concept for dead area reduction by developing a P1-filling process (< 80 μm printed filling width) for laser structured/patterned trenches of ~50 μm width. With the right combination of carefully selected material interface, inkjet printhead, deposition settings, pattern digitalization & other parameters, we are able to develop an industry relevant micro-filling process. And, show an increase in the performance of PV cells, as compared to the reference modules. The results lay the foundation for direct up-scaling to industrial-size substrate areas and open up the possibility to realize all kinds of advanced interconnect schemes for the next generation thin-film CIGS PV modules. • Digital manufacturing of P1-filling for the thin-film photovoltaics in conjunction with laser process. • Approach towards reduction of dead-area in photovoltaics. • Inkjet printing of functional material within μm range channels/trench (< 80 μm). • Increase in photovoltaic performance (fill factor & module efficiency). • P1-filling process developed under ambient condition, without any inert atmosphere.

Comparative assessment of offshore floating photovoltaic systems using thin film modules for Maldives islands

Floating photovoltaic systems has a high potential for large-scale power generation when introduced on the offshore location. These systems help to boost the renewable power generation in islands with minimal land availability. In this context, this study presents the electrical performance of offshore floating photovoltaic systems in Maldives Islands. Offshore floating photovoltaic systems of 5 MW installed capacity using thin-film modules were considered for implementation on four offshore locations. Numerical analyses were carried out to assess the electrical performance of the systems and the results were compared with floating photovoltaic system at a lake and a ground mounted photovoltaic system. The results revealed that the thin film-based offshore floating photovoltaic systems increase the annual energy yield by 13 % and 14 % compared to that of pontoon mounted and ground mounted systems, respectively. The performance ratio of the offshore systems was higher than that of other systems, with the maximum value of 87.10 % and annual energy yield of 8.74 GWh. The cost analysis indicates that the cost of ground mounted system is 72 % higher than that of floating systems. The carbon footprint analysis revealed that the offshore systems can reduce the carbon emission by about 14 % higher than that of other systems.

Favorable Bonding and Band Structures of Cu2ZnSnS4 and CdS Films and Their Photovoltaic Interfaces.

Thin-film photovoltaic cells using Cu2ZnSnS4 (CZTS, p-type) have many advantages, such as high photoconversion, low cost, and great tunability with earth-abundant, nontoxic elements, all of which are necessary to be long-term contributors to next-generation solar energy harvesting. Accurate measurements of bonding and band structures of both the thin-film materials and their interfaces are paramount to designing the solar devices layer-by-layer. Here, finely tuned 1 μm thick CZTS films, 50 nm thick CdS layers (n-type), and their 1 μm/2 nm p-n junction were fabricated inexpensively using our previously studied methods and investigated extensively for maximizing the key interface in the CZTS solar devices. Synthesized bulk CZTS and CdS were analyzed for structural deviations and crystal defects using synchrotron-based (SR) X-ray absorption fine structure (XAFS) along with simulated XAFS patterns. The structural properties of the two materials were designed to favor photovoltaic activity. Interface valence band structures of the CZTS/CdS p-n junction were measured through SR X-ray photoelectron spectroscopy (SR-XPS) and compared with the ones simulated using density functional theory. A full band diagram was constructed from XPS of the bulk films and SR-XPS of the interface, providing guidelines in optimizing charge-carrier extraction from the CZTS absorber to CdS buffer layer. It turns out that a small spike-like interface in the conduction band overlap was formed, maintaining a strong internal bias, while favoring a small energy barrier to prevent large-scale recombination from occurring. A large open-circuit voltage was obtained in the preliminary solar cell devices built on the small spike-like interface.

Probing the Density of States of Organic and Perovskite Semiconductors By Energy-Resolved Electrochemical Impedance Spectroscopy

The performance of thin-film photovoltaic cells is closely related to the energy alignment of the absorber layers and charge collection layers used for constructing the device and is further influenced by the presence of energetic disorder and defects in the photoactive material. This especially holds for novel organic and perovskite semiconductors, where film processing conditions, such as solvents used, thermal or solvent vapor annealing, and aging of the active materials are known to have an influence on the device performance. Knowledge about the energy of the relevant frontier orbitals such as HOMO and LUMO for organic semiconductors,[1]and valence (VB) and conduction (CB) bands for perovskites is key to designing more efficient materials. In addition, the energetic disorder, such as broadening of the band edges and states that appear in the bandgap are strongly affecting solar cell efficiencies. Knowledge about the density of states close to and inside the bandgap is very relevant in this respect.In this work energy-resolved electrochemical impedance spectroscopy (ER-EIS) as advanced by Nádazdyet al.[2]is applied on various organic bulk-heterojunction and lead-halide perovskite semiconductors to map their energy landscape around and in the band gap. ER-EIS provides a direct electrochemical measurement of the HOMO/VB and LUMO/CB energies, but also resolves band tails and sub-bandgap states with a resolution of up to six orders of magnitude. This enables detection of subtle but important effects that are the consequence of layer processing conditions such as spin coat parameters, solvent combinations, thermal annealing time and temperature, and atmospheric exposure (vacuum, inert, air).We will present experiments that aim to quantify relative changes in the energy landscape due to varying processing conditions and assign physical meaning to these changes (e.g. morphology and (un)intentional doping). The systems under investigation are well-known donor-acceptor bulk-heterojunction (e.g., P3HT:PCBM and PM6:Y6) and triple-cation mixed-halide perovskites (CsFAMA). The results shed new light on largely unknown defect states in the bandgap of solution-processed semiconductors.[1] R. E. M. Willems, C. H. L. Weijtens, X. de Vries, R. Coehoorn, and R. A. J. Janssen, Relating frontier orbital energies from voltammetry and photoelectron spectroscopy to the open-circuit voltage of organic solar cells, Adv. Energy Mater. 2019, 9, 1803677.[2] V. Nádazdy, F. Schauer, and K. Gmucová, Energy resolved electrochemical impedance spectroscopy for electronic structure mapping in organic semiconductors, Appl. Phys. Lett. 2014, 105, 142109.

High-yield recycling and recovery of copper, indium, and gallium from waste copper indium gallium selenide thin-film solar panels

A separation process for Cu, In, Ga, and Se (CIGS)-based thin-film solar panels is proposed in this study. Initially, the separation process, by peeling off the panels in a layer-by-layer manner, was achieved by utilizing the different thermal strains of materials inside the CIGS solar panels. Subsequently, the recovery process was performed by annealing the CIGS layers for the removal of Se, and then leaching was performed with nitric acid, followed by the individual extraction of valuable metals. The pH values, concentrations of extractant, stripping agents, organic-aqueous ratios, and reaction time were investigated in detail to optimize the separation conditions for Cu, In, and Ga. First, In was extracted using di-(2-ethylhexyl) phosphoric acid into the organic phase, while Cu and Ga remained in the aqueous phase, by controlling the extraction conditions. After the extraction of In, Ga was extracted using the same extraction agent under different conditions, and nearly pure Cu remained in the residual aqueous solution. Ammonium hydroxide was added to three solutions to form metal hydroxide precipitates. Under the optimal conditions, a recovery rate of >90% could be achieved for In, Ga, and Cu. Furthermore, all as-formed hydroxides were recycled and converted into metal oxides with a purity of >99% by calcination. These findings can provide a pathway for the effective recycling and recovery of Cu, In, and Ga from waste CIGS thin-film solar panels. • A facile and practical method to separate and recover valuable metals respectively from the real commercial thin-film solar panel was demonstrated. • A novel and low-cost physical separation process was induced to peer off the solar panel layer by layer via the extremely low-temperature liquid nitrogen treatment. • An extraction and stripping process was designed to separate Cu, In, and Ga from a complicated multi-element system individually. • Highly pure valuable metal oxides were recovered as the final products, establishing a possible curcular economy model for waste solar panel recycling and recovery.

ГИДРОТЕРМАЛЬДЫ ӘДІСПЕН МЫРЫШ ОКСИДІНІҢНАНОСТЕРЖЕНЬДЕРІН АЛУ

Thin films of zinc oxide (ZnO) are very promising for thin-film transistors, solar panels, sensors and optoelectronic devices. The article presents the structural properties and morphology of zinc oxide (ZnO) obtained by hydrothermal synthesis. ZnO nanofilms (as a seed layer) were deposited by the sol-gel method on the glass surface of STO. The results of the experiment showed that the concentration of chemical reagents in the process of sol-gel transformation has a strong effect on the properties of ZnO films. Samples of ZnO nanorods on the surface of the nanofilm were obtained by hydrothermal method at a solution temperature of about 97 ° C for 3 hours.After firing the synthesized ZnO nanorods, the electrical resistance increased several times. The chemical composition and morphology of the obtained nanorods arrays were characterized by scanning electron microscopy and X-ray diffraction. As a result of the study, arrays of ZnO nanoparticles showed a highly improved response to visible light. The results of the article can be used in other combinations of metal oxides, and also offer many interesting opportunities for further development of high-performance photoelectrochemical devices for solar energy conversion. The results of scientific research are the most important material data for alternative energy and can be used by industry specialists in the creation of photoelectrochemical systems for generating hydrogen fuel with the formation of active photanode layers of water decomposition systems with zinc oxide.

Effect of tilt angle on the performance of a thin-film photovoltaic system

Solar energy is among the cleanest and most sustainable ways to enhance electrical supply's resiliency and reliability for domestic and industrial use. A Photovoltaic (PV) system is the most effective way of capturing solar energy. Long-term warranty, low-cost maintenance, and vast resource availability, solar power generation has an advantage over other approaches. Thin-film technology PV cells are a new kind of solar cell that offers an efficient technique of generating electricity from sunlight. The thin-film PV technology (FFMAT-10, Renovagen, UK) used in this study can supply 0.9 to 1.6 kW of energy to the fast-fold energy hub. The hub’s system status and configuration display battery power input, battery’s state of charge, thin-film PV power and AC power output. Two fast-fold mats (with a surface area of 25.3 m2) were connected to the energy hub. Increasing energy demand coupled with frequent power outages, and inaccessibility of electricity in rural areas necessitates the usage of PV systems at their best performance level. The study objective, therefore, sought to assess the effect of tilt angle on the performance of the thin-film PV system. The study was conducted at Kimicha in Kirinyaga County Kenya, and Juja, Kenya at tilt angles between 0o to 30o. The results indicated that the mean peak PV power for Kimicha was 347.8±231.9 W at 5o and 517.7± 131.3 W at 15ofor Juja. The maximum solar radiation during the study period was 1086.4 ±211.4 W/m2 for Juja and 973.5±219.93 W/m2 for Kimicha. From the study, it was realized that an optimal tilt angle yields optimum solar radiation that translates to maximum power production. Even though the study was conducted in two different regions, it may be applied to any other geographical location. The outcome of the study aids in acquiring self-sustaining power in the most remote locations where electricity is scarce as well as improving energy security.

Optimal identification of model parameters for PVs using equilibrium, coot bird and artificial ecosystem optimisation algorithms

Realising an accurate estimation of model parameters for solar cells and the Photovoltaic modules has serious importance for enhancing the performance of their control systems. Three neoteric metaheuristic methods of Artificial Ecosystem-based optimisation, Coot Bird-based optimisation, and Equilibrium optimiser have been applied and evaluated concerning the accurate estimation of various Photovoltaic models. The validation of the applied methods has occurred for valuing the model parameters of R.T.C. France solar cell, and Thin-film ST40 Photovoltaic module. The objective function has been formulated as the Root Mean Square Error between the actual and estimated data. Matlab/Simulink has been used for the verification of the optimisation methods. The outcomes demonstrate that: (1) The three optimisation algorithms can resolve the problem of the Photovoltaic parameter estimation; (2) There are small distinctions between the three algorithms concerning their best value of the impartial function; this distinction between the best and worst algorithm is 10–9 for R.T.C. France solar cell for SDM; (3) The best algorithm considering the best value of the objective function is Artificial Ecosystem-based optimisation for R.T.C. France solar cell; (4) Statistical results prove that the three algorithms have tracking efficiencies of 100%, 99.999%, and 98.285% for Artificial Ecosystem-based optimisation, Coot Bird-based optimisation, and Equilibrium optimiser, respectively, based on 10 individual runs for R.T.C. France solar cell for SDM. Moreover, the simulation results show that the I/V curves obtained employing Artificial Ecosystem-based optimisation, Coot Bird-based optimisation, and Equilibrium optimiser techniques were also matched with the corresponding datasheet curves with the Artificial Ecosystem-based optimisation and Coot Bird-based optimisation's predominance in standings the convergence speed, tracking efficiency, statistical indices, and solution accuracy.

33‐2: Invited Paper: Flexible OLED Displays with Ink‐Jet Printing Technology

TCL CSOT has been investing in ink‐jet printing AMOLED technology for many years, and now CSOT has mastered the complete manufacturing process for IJP display technology, including rigid and flexible technology to manufacture middle and large size OLED displays. Flexible technologies such as panel design, substrate, TFT backplane, EL device, thin film encapsulation, module, and compensation have been developed. Attractive flexible prototypes including 14~31‐inch OLED have been demonstrated in the past three years. TCL CSOT expects to provide innovative flexible OLED displays in the near future.

New model to study the outdoor degradation of thin–film photovoltaic modules

The performance of four thin-film photovoltaic modules is analyzed after an initial stabilization period and a subsequent outdoor exposition. The seasonal variations and the degradation rates of a single-junction hydrogenated amorphous silicon (a-Si:H) module, a tandem amorphous microcrystalline Silicon (a-Si/μc-Si) module, a heterostructure cadmium sulfide-cadmium telluride (CdS/CdTe) module and a copper indium gallium selenide (CIGS) are examined and correlated to spectral changes. The I–V curves have been measured every 5 min; the electrical parameters and parasitic resistances have been identified. By exploiting a number of experimental measurements acquired within a narrow interval of irradiance and cell temperature, a novel mathematical model has been developed and fitted: it considers a stationary seasonal variation component and a linear long-term degradation component. The results show annual power degradation rates of 4.0% for the a-Si:H module, 3.4% for the a-Si/μc-Si and 3.5% for the CdS/CdTe, whereas for the CIGS module the annual degradation is not significant, i.e. 0.2%.