Efficient hole transport layers based on cross-linked poly(N-vinylcarbazole) for high-performance perovskite photodetectors

Hole transport layers (HTLs) play a significant role in organic–inorganic hybrid perovskite (OIHP) photodetectors for effective hole extraction and transport, energy level alignment, and interface optimization. To date, poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are commonly used as HTLs, but both of them have some disadvantages that affect the performance of devices, such as high hydrophobicity, intrinsic hydrophilicity and acid nature. Herein, a p-type cross-linked polymer material poly(N-vinylcarbazole) (PVK) doped with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), has been explored as an efficient HTL and was first introduced in p–i–n type OIHP photodetectors. The non-wetting PVK HTL leads to large perovskite grains, and the F4TCNQ assists hole extraction and transport in interfaces, and even reduces the carrier recombination. The champion device demonstrates over 80% external quantum efficiency (EQE) with a striking increase of 20% compared with the dopant-free devices. Additionally, the optimal doped device exhibits a low dark current density of 5.23 × 10⁻⁴ mA cm⁻² under −0.1 V. As a result, this work provides a novel candidate for a solution-processed HTL to achieve high-performance OIHP photodetectors.