Effects of air exposition on series and shunt resistances of a solar cell based on PTB7-Th:PC_(71)BM

摘要

Much has been reported on the effects of air action on the physical entities related to the transport processes in organic solar cells, for example, the electronic mobility, the lifetime of the charge carriers and the recombination kinetics. These effects have a direct impact on the series and parallel resistances (R-s and R-sh) of the solar cell, but studies of the action of the air environment on these resistances have been little explored. Here we present an experimental study of the environment action on an ITO/PEDOT:PSS/PTB7-Th:PC71BM/Ca/Al device, exploring mainly the variation of the series and the shunt resistances with the air exposure time. We used the classical equation of the current-voltage of an equivalent circuit of a solar cell to fit the experimental results, and used R-s and R-sh as adjustment parameters. We also correlated these resistances with the fill factor by the help of an approach developed by M. A. Green in 1982.