A setup for studying stability and degradation of polymer solar cells

A detailed description of a setup for studying ageing of polymer devices is presented. The system offers individual control of the environmental factors (oxygen, humidity, atmosphere, temperature and light intensity) causing the degradation of organic devices. The system was developed for accurate control of the conditions and data collection of photovoltaic (PV) parameters for organic solar cells during long-term testing. The atmosphere chamber can operate under vacuum conditions without temperature control. It is designed for operation at an internal gas pressure of around 1 atm. It is further equipped for isotopic labeling experiments of the internal atmosphere (18O2 and H218O) such that degradation mechanisms can be studied using TOF-SIMS as a chemical probe. Experiments on both “accelerated” (by applying thermal stress to the devices) and “long-term” lifetime measurements of traditional organic bulk heterojunction solar cell devices have been realized while controlling the environmental conditions. As an example of use of the setup we determined the acceleration factor for standard bulk heterojunction devices based on ITO/PEDOT:PSS/P3HT-[60]PCBM/Al when operated under an ambient atmosphere and under an inert atmosphere at temperatures of 25, 43, 63 and 83 °C. Different values for the acceleration factor were found depending on the atmosphere used and further our results suggest that the acceleration factor may change in time as different degradation mechanisms may dominate at different times during the device life.