Characteristics change in organic photovoltaics by thermal recovery and photodegradation

It has been reported that organic photovoltaic modules exposed to the outdoors show rapid degradation in the initial stage and gradual degradation after that. It is elucidated in this study that seasonal variation with an increase and a decrease in output power, respectively, in summer and winter occurs during the gradual degradation stage. Such variation did not completely disappear even after output power was corrected by the temperature coefficient obtained by the indoor temperature dependence of output power. The difference between performance ratios with and without correction by the temperature coefficient was 0.05. It was also clarified that seasonal variation is determined by the balance between thermal recovery with increasing output power and photodegradation. Thermal recovery requires the duration for the module temperature over 30 degrees C to exceed 100 h. (C) 2019 The Japan Society of Applied Physics