Analysis of degradation mechanisms in donor-acceptor copolymer based organic photovoltaic devices using impedance spectroscopy

作者：Srivastava S B; Sonar P; Singh S P^*

来源：Materials Research Express, 2016, 3(9): 096202.

DOI：10.1088/2053-1591/3/9/096202

• charge transport
• charge carrier lifetime
• degradation mechanism
• impedance spectroscopy
• organic solar cell

The stability of organic photovoltaic (OPV) devices in ambient conditions has been a serious issue which needs to be addressed and resolved timely. In order to probe the degradation mechanism in a donor-acceptor polymer PDPP-TNT: PC71BM bulk heterojunction based OPV devices, we have studied current density-voltage (J-V) behavior and impedance spectroscopy of fresh and aged devices. The current-voltage characteristic of optimized fresh devices exhibit a short circuit current density (J(sc)) of 8.9 mA cm(-2), open circuit voltage (V-oc) of 0.79 V, fill factor (FF) of 54.6%, and power conversion efficiency (PCE) of 3.8%. For aged devices, J(sc), V-oc, FF, and PCE were reduced to 57.3%, 89.8%, 44.3% and 23.7% of its initial value, respectively. The impedance spectra measured under illumination for these devices were successfully fitted using a CPE-based circuit model. For aged devices, the low-frequency response in impedance spectra suggests an accumulation of the photo-generated charge carriers at the interfaces which leads to a significant lowering in fill factor. Such degradation in device performance is attributed to the incorporation of oxygen and water molecules in devices. An increase in the recombination resistance indicates a deterioration of free charge carrier generation and conduction in devices.

• 出版日期2016-9