Achieving efficient inverted planar perovskite solar cells with nondoped PTAA as a hole transport layer

Inverted planar perovskite solar cells (PSCs) with a poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) layer as the hole transport layer (HTL) are shown to exhibit high power conversion efficiency (PCE). To date, efficient PTAA HTLs have required dopants to increase conductivity. These dopants, which include 2,3,5,6-tetrafluoro- 7,7,8,8-tetracyanoquinodimethane and bis(trifluoromethane) sulfonimide lithium salt/4-tert-butylpyridine, are harmful to the stability of the devices and may increase the cost of the PSCs. We realized efficient inverted planar PSCs with nondoped PTAA as the HTL. We used contact angle, absorption spectra, X-ray diffraction, fluorescence spectra, and atomic force microscope to measure the impact of nondoped PTAA on the upper perovskite films. The results showed that the nondoped PTAAs work as effectively as the doped ones. The inverted planar PSCs based on nondoped PTAA exhibited relatively excellent performance. We achieved a higher PCE of 18.11% and a very small hysteresis index of 0.32% were using a very thin nondoped PTAA film. This efficient nondoped HTL provided an easy way for inverted planar PSCs to solve problems introduced by dopants. This study provides a reference for the future preparation of highly efficient and stable PSCs with nondoped HTL.