The present study analyses the degradation of thin film photovoltaic modules corresponding to four technologies: a-Si:H, a-Si:H/µc-Si:H, CIS and CdTe, under 5 years of outdoor long term exposure in Leganés, Spain. The period of outdoor exposure ranges from January 2011 to December 2015. The degradation rate and the stabilization period are analysed by using two different techniques. Moreover, the evolution of the fill factor and performance ratio is assessed. The CdTe module was found to have the highest degradation rate:-4.45 %/year, while the CIS module appears to be the most stable with a degradation rate of -1.04 %/year. The a-Si:H and a-Si:H/µc-Si:H modules present stabilization periods of 24 and 6 months respectively. The CdTe module degrades significantly for a period of 32 months, while the CIS module is the least degraded PV specimen over the whole experimental campaign.

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