Field‐Effect Control in Hole Transport Layer Composed of Li:NiO/NiO for Highly Efficient Inverted Planar Perovskite Solar Cells

Perovskite solar cells (PSCs) have been recognized as fascinating optoelectronic devices with a rapid progress of the power conversion efficiency (PCE). However, serious carrier recombination at charge transport layer (CTL)/perovskite interface limits further development of PSCs. Therefore, carrier dynamics at interface should be finely regulated to achieve a satisfied performance. Herein, a hole transport layer (HTL) is developed with a bilayer film composed of Li:NiO/NiO, in which NiO directly contacts with perovskite film. The prepared HTL is a p‐p+ homojunction as Li:NiO film has higher concentration of carrier than NiO. Energy level alignment in Li:NiO/NiO HTL reflects a hole transport improvement by both built‐in electric field and interface effective field. The additional drive forces generated by the above field effects in HTL present a significant enhancement for carrier extraction and transport at HTL/perovskite interface. As a result, the inverted planar PSC with the Li:NiO/NiO HTL delivers an improved PCE up to 19.04% from 15.40% of the control one, which also shows a high fill factor of 82.83%, indicating a low level of carrier nonradiative recombination. This work provides new insights on the carrier dynamics control in CTL/perovskite interface, which is meaningful for designing excellent PSCs. A hole transport layer (HTL) with bilayer film composed of Li:NiO/NiO homojunction is developed for inverted planar perovskite solar cell. The built‐in electric field and effective field in the homojunction both stimulate hole transfer from NiO to Li:NiO. The additional drive forces present a significant enhancement for carrier transport at HTL/perovskite interface to achieve a device efficiency up to 19.04%.