Influence of the interface material layers and semiconductor energetic disorder on the open circuit voltage in polymer solar cells

Abstract

ABSTRACT Material layers at electrode/semiconductor interfaces are fundamental for the photovoltaic properties of polymer solar cells. The relationship between open‐circuit voltage ( V OC ) and the work function ( φ ) of these interface layers is still a matter of debate. Simulations, together with experiments on over more than 20 cell architectures based on P3HT:PC 60 BM, enabled us to analyze the physical dependence of V OC on φ . In particular, when the work function of the contacts is well inside the gap we observe that performance depends strongly on even small variations of φ . On the other hand, when it approaches the energy levels of the semiconducting polymers, device operation becomes the most efficient and less sensitive to variations in φ . Furthermore, by varying the Gaussian density of states (DOS) of the active blend we were able to show that V OC performance depends significantly also on the DOS. Our study based on the simultaneous variation of transport layers represents a promising method to optimize the design and performance of polymer solar cells. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53 , 690–699