Improved current density of inverted perovskite solar cells via hole transport layer doping

Abstract

Inverted planar perovskite solar cells (PSCs) with a hole transport layer (HTL) made of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) exhibit high power conversion efficiency (PCE). In this study, we introduce a dopant, tris[3,5-bis(trifluoromethyl)phenyl]phosphine (T35FP), into the PTAA HTL. T35FP notably enhances hole extraction and concurrently improves the perovskite layer's quality by reducing defects, resulting in improved current density. Consequently, by improving the energy band alignment and minimizing defects, doped PTAA-based PSCs can achieve a 20.69% PCE, a significant improvement over the 18.50% PCE of a PSC with undoped PTAA. Furthermore, the long-term stability of the doped PTAA-based PSC is demonstrated under ambient conditions without encapsulation. The device retains 62% of its initial PCE after 500 hours under our experimental conditions, while the undoped device experiences a drop to 38% of its initial PCE. Our study confirms that the straightforward process of HTL doping can be applied to the design of stable and high-performance inverted PSCs.