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This paper reports the results of an international interlaboratory comparison study on light‐ and elevated temperature‐induced degradation (LETID) on crystalline silicon photovoltaic (PV) modules. A large global network of PV module manufacturers and PV testing laboratories collaborated to design a protocol for LETID detection and screen a large and diverse set of prototype modules for LETID. Results across labs indicate the reproducibility of LETID testing is likely within ±1% of maximum power (PMP). In intentionally engineered LETID‐sensitive modules, mean degradation after the prescribed detection stress is roughly 6% PMP. In other module types the LETID sensitivity is smaller, and in some we observe essentially negligible degradation attributable to LETID. In LETID‐sensitive modules, both open‐circuit voltage (VOC) and short‐circuit current (ISC) degrade by a roughly similar magnitude. We observe, as do previous studies, that LETID affects each cell in a module differently. An investigation of the potential mismatch losses caused by nonuniform LETID degradation found that mismatch loss is insignificant compared to the estimated loss of cell ISC, which drives loss of module ISC. Overall, this work has helped inform the creation of a forthcoming standard technical specification for LETID testing of PV modules, IEC TS 63342 ED1, and should aid in the interpretation of results from that and other LETID tests. [ABSTRACT FROM AUTHOR]

According to the International Technology Roadmap for Photovoltaics, passivated emitter and rear solar cells dominate the market in 2021 of up to 80% and are forecast to remain state of the art at least for the next 5 years. Within the production process of solar cells, it is typical to have cells with lower efficiency grades due to variations in manufacturing processes or material defects. Reprocessing such solar cells could save cost due to increased production yield and simultaneously reduced cost for recycling of unusable/unsellable low‐efficiency cells. Herein, the impact of the laser‐enhanced contact optimization (LECO) process on the power output and reliability of solar modules using commercial off‐spec cells of different manufacturers is analyzed. LECO is a downstream process for optimizing metal−semiconductor contacts on finished solar cells. The treatment leads to a significant economic gain due to enhanced cell efficiency (Wp ↑, therefore manufacturing cost per Wp ↓) even of already good solar cells. Herein, the first evaluation of the impact of the LECO process on the cell output power on an industrial scale (>1000 cells) and on module reliability is presented. The results for common short‐term effects like light‐induced degradation and light‐ and elevated temperature‐induced degradation are within expected limits and the durability against, for example, potential‐induced degradation is not changed due to the LECO process. The results further show that cell sorting is crucial for a reliable module and to avoid outliers in terms of unexpected degradation and recovery phenomena of individual cells. [ABSTRACT FROM AUTHOR]

Recent research demonstrates several failure modes of photovoltaic modules operating under high electric potentials. In crystalline-silicon modules, the predominant failure mode is potential-induced degradation (PID), causing dramatic power losses in systems under high voltage and critical polarity. Environmental conditions highly influence the degradation behavior. The ability to reproduce field observation in the laboratory is challenging and not all stressors can be checked simultaneously. PID and its root cause are not fully understood, but we know several mechanisms are working simultaneously and at varying rates. The main mechanisms are degradation, characterized by ion diffusion and cell shunting, and recovery, driven by temperature, voltage, and potential. Most studies have focused on simulating module degradation using a constant set of parameters. However, field exposure to high voltage is variable, measured by the hour. In 2012, Nagel presented a module stability test with varying environmental conditions, notably temperature. To investigate PID remedies, this research develops a testing procedure that reproduces field observations while understanding that some modules do not degrade in real PV installations under high potentials. Conductive foil is applied to the front side of the module and voltage cycling is introduced to examine potential-induced degradation and potential-induced recovery behavior. The relationship between the two defines a PID stability criterion. Results show general PID sensitivity and suitable remedies for PID affected systems. PID recovery and protection solutions include applying recovery potential at night, and potential shifting, which regulates potential for the module string. This paper explores possible degradation mechanisms, recovery of module output power and PID stability criteria. [ABSTRACT FROM AUTHOR]