Identification of degradation mechanisms in field‐tested CdTe modules

Field tests and accelerated ageing tests were conducted on CdTe photovoltaic modules with Sb‐based back contacts. Significant performance degradation was observed during one and a half years of outdoor exposure. Small‐area samples were prepared from field tested modules and characterized with current–voltage, capacitance–voltage and resistance measurements. Results show that module performance degradation in the field can be partly attributed to a decrease in doping concentration close to the CdS/CdTe junction and an increased resistance in the transparent front contact. A comparison with results in the literature indicates that bias voltage may play a role in the degradation process.