F4-TCNQ doped strategy of nickel oxide as high-efficient hole transporting materials for invert perovskite solar cell

Abstract Nickel oxide (NiOx) as a promising hole transport material based on inverted perovskite solar cells has advantages of low cost, high photo stability and small hysteresis. However, low carrier transport capacity and rough surface morphology leading to serious interface recombination are limited the improvement of photoelectric conversion efficiency. In this work, 2,3,5,6-Tetrafluoro-7,7,8,8 tetracyanoquinodimethane (F4-TCNQ), a high temperature resistant small molecule material, was doped into the NiOx hole transport layer (HTL) by sol-gel method in order to achieve band adjustment and optimize the surface contact performance of perovskite substrate. As a result, a higher recombination resistance (18804Ω) is obtained comparing the reference device (5349Ω). And the conversion efficiency of the optimized device with doping transport layer increased to 15.7%, which was 16.2% higher than the undoped transport layer. The charge separation and hole mobility derived from the perovskite/HTL interface are enhanced. The rational design of the p-type molecule doped NiOx substrate strategy provides desired solution for future development of inverted based perovskite solar cells.