Various types of next-generation encapsulation films based on polyolefins have recently been introduced and could attract market attention. These material innovations can be classified as polyolefin elastomer (POE) and thermoplastic polyolefin (TPO) encapsulants, both of which consist of a polyethylene backbone with different side groups. The main advantage of these materials is the replacement of the vinyl acetate side groups of state-of-the-art encapsulant ethylene vinyl acetate (EVA) so that acetic acid cannot be formed. The main objective of this paper is to investigate the material properties of next-generation encapsulant films and compare them to an EVA reference. Two commercially available EVA alternatives (POE and TPO) have been selected. The material properties of single films as well as the electrical performance of test modules using these different encapsulants were investigated. The different films show comparable optical, thermal and thermo-mechanical properties, with slight differences in UV transparency and melting temperatures. Only shear viscosity values are higher for TPO than for POE and EVA, which requires adaption of the photovoltaic (PV) module lamination parameters. The test modules comprising the different encapsulation films show minor differences in the electrical performance after manufacturing; upon accelerated aging, no significant power loss is observed. But compared to TPO or POE, after 3000 h of damp heat exposure, test modules with EVA show the beginning of corrosion effects at the silver grid and above the ribbons. Based on the results, it can be stated that the new polyolefin encapsulation materials show great potential to be a valid replacement for EVA.

As the PV market shows enormous potential with huge growth rates especially in climatic‐sensible regions, specific artificial ageing test procedures are a key point for an efficient and fast product development of new PV modules/materials optimized for the use in specific climatic regions. Based on the definition of four climate profiles (dry and hot—arid, moderate, humid, and hot—tropical and high irradiation—alpine), a program was worked out with 14 climate specific test conditions for accelerated ageing tests. The big challenge in this respect was the adaption/advancement of existing standard procedures for PV modules/components testing in a way that reliable testing for certain climatic conditions optimized PV modules is possible. The time‐dependent repeated application of combined climatic and environmental stresses (temperature, temperature cycles, humidity, irradiation, mechanical load, salt mist) was used to induce performance losses, material degradation, and failures in test modules which resemble those effects occurring in real‐life PV installations under comparable climatic and environmental conditions. For this demanding task, a large number of identical test modules with respect to composition and module design was manufactured. A detailed nondestructive analysis/characterization of all modules was performed: (1) before; (2) during (six intermediate stages); and (3) after the accelerated ageing test. The nondestructive characterization methods used to follow the module's ageing processes throughout the whole accelerated ageing procedure were current‐voltage characteristics measurements and electroluminiscence images for the electrical performance evaluation and ultraviolet fluorescence (spectroscopic and imaging) measurements, Fourier transform infrared spectroscopy as well as colour measurements of the backsheets outer layer for recording of chemical changes of the encapsulant and backsheet. The electrical and material characterization data were incorporated in an optimized database. As stated above, a set of three identical modules was exposed together in the respective climate specific ageing tests and subsequently characterized in order to increase statistical reliability of the measuring results. The analysis of the data and first approaches of advanced data treatment have already clearly shown that the electrical and material degradation of the test modules is dependent on (1) the type and combination, (2) duration, and (3) mode (sequential versus constant) of the stresses applied. On the one hand, the simulation of environmental stresses like heavy snow and wind load and enhanced frequency of temperature cycling resulting in cell cracks and cell connector breakage could be demonstrated. Additional treatment in salty atmosphere, on the other hand, did not show an accelerating effect on degradation on the electrical or material side. The accelerating effect of enhanced temperature, humidity, or additional irradiation on the degradation of power and materials could be shown very well. D...

In this paper, indium-doped zinc oxide (IZO) films were grown by spray pyrolysis, using zinc acetate and indium acetylacetonate precursors. The focus was on developing a solution recipe based on water as solvent, with only minor acetic acid content, as well as keeping the substrate temperature as low as possible-at 360°C. The process is therefore environment friendly and energy efficient. Despite the challenging conditions, the resulting IZO films were highly transparent and conductive. Their texture deviates strongly from the (002) texture of ZnO and depends on the indium content, which also influences the resistivity. The latter attains its minimum for an indium concentration of 4 at.% in the solution and decreases for increasing film thickness, reaching the value of (5.0 ± 0.1) 9 10 -3 X cm, mainly due to the increase in carrier mobility. The stability of the resistivity after high dose of UV irradiation was found to increase with the carrier density and the film thickness. Thick, highly doped films show minimal resistivity modification even after a total dose of 12.1 kJ/cm 2 UVA/ UVB irradiation. Finally, to demonstrate its applicability in devices, the IZO electrode was used for the fabrication of a lead-perovskite absorber solar cell, yielding an energy conversion efficiency of 6% and 910 mV open-circuit voltage.

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Several series of six-cell photovoltaic test-modules-intact and with deliberately generated failures (micro-cracks, cell cracks, glass breakage and connection defects)-were artificially and naturally aged. They were exposed to various stress conditions (temperature, humidity and irradiation) in different climate chambers in order to identify (i) the stress-induced effects; (ii) the potential propagation of the failures and (iii) their influence on the performance. For comparison, one set of test-modules was also aged in an outdoor test site. All photovoltaic (PV) modules were thoroughly electrically characterized by electroluminescence and performance measurements before and after the accelerated ageing and the outdoor test. In addition, the formation of fluorescence effects in the encapsulation of the test modules in the course of the accelerated ageing tests was followed over time using UV-fluorescence imaging measurements. It was found that the performance of PV test modules with mechanical module failures was rather unaffected upon storage under various stress conditions. However, numerous micro-cracks led to a higher rate of degradation. The polymeric encapsulate of the PV modules showed the build-up of distinctive fluorescence effects with increasing lifetime as the encapsulant material degraded under the influence of climatic stress factors (mainly irradiation by sunlight and elevated temperature) by forming fluorophores. The induction period for the fluorescence effects of the polymeric encapsulant to be detectable was~1 year of outdoor weathering (in middle Europe) and 300 h of artificial irradiation (with 1000 W/m 2 artificial sunlight 300-2500 nm). In the presence of irradiation, oxygen-which permeated into the module through the polymeric backsheet-bleached the fluorescence of the encapsulant top layer between the cells, above cell cracks and micro-cracks. Thus, UV-F imaging is a perfect tool for on-site detection of module failures connected with a mechanical rupture of solar cells.