Influence of p-type doping on perovskite solar cells fabricated with dithiophene-benzene copolymer as the hole-transporting layer

Abstract

We fabricated perovskite solar cells (PSCs) employing high and low molecular weight dithiophene-benzene (DTB) copolymers as hole-transporting materials under nitrogen atmosphere. We then measured current density-voltage (J-V) characteristics of PSC devices in ambient air. After exposure to air for 5 h, device performance was poor and power conversion efficiency (PCE) was 3.05%. However, device performance gradually improved when the device was kept in dry air, and PCE was 16.20% after 173 h. This result indicates that the carrier density of DTB increased due to oxygen-doping. After oxygen-doping reached saturation, the superior molecular order of the high molecular weight DTB-based device yielded a higher PCE than the low molecular weight DTB-based device. When tris(pentafluorophenyl)borane (BCF) was added to DTB, the initial characteristics improved (PCE = 12.12%) further (PCE = 16.89%) by oxygen-doping, yielding the maximum PCE in this study.