Modulating buried interface with multi-fluorine containing organic molecule toward efficient NiOx-based inverted perovskite solar cell

Inverted perovskite solar cells (p-i-n PSCs) with nickel oxide (NiOx) as hole transport layer (HTL) have attracted tremendous attention due to the stable performance and ease of preparation. However, the NiOx/perovskite interface in the inverted perovskite solar cells (p-i-n PSCs) usually suffers from energy level mismatch, low conductivity, lattice mismatch, existence of surface defects etc., limiting the improvement of power conversion efficiency (PCE) and durability. Fluorine-containing materials have desired interface modification effect and are popular in the bulk and upper interface of perovskite, but rarely appear at NiOx/perovskite interface to address above issues. Herein, an interfacial modification strategy with a multi-fluorine organic molecule 6FPPY, is proposed to manage the buried interface of NiOx-based p-i-n PSC. Theoretical calculation and experimental results show that 6FPPY bridges the NiOx/perovskite interface through moieties with F atoms, producing a NiOx film with higher hole transport efficiency, releasing the residual strain of perovskite film, passivating the NiOx/ perovskite interface defects, and suppressing the detrimental reaction between NiOx and perovskite. Consequently, p-i-n PSCs with 6FPPY-modified NiOx achieve a champion PCE of 24.0%, which is superior to the reference device. After 6FPPY modification, PSC can retain above 90% of the initial PCE after 200 h illumination at maximum power point in N2 atmosphere and exhibit better stability than the reference device during 1080 h storage under 60% humidity and 30-35 celcius.