High-Hole-Mobility Metal-Organic Framework as Dopant-Free Hole Transport Layer for Perovskite Solar Cells

A dopant-free hole transport layer with high mobility and a low-temperature process is desired for optoelectronic devices. Here, we study a metal-organic framework material with high hole mobility and strong hole extraction capability as an ideal hole transport layer for perovskite solar cells. By utilizing lifting-up method, the thickness controllable floating film of Ni₃(2,3,6,7,10,11-hexaiminotriphenylene)₂ at the gas-liquid interface is transferred onto ITO-coated glass substrate. The Ni₃(2,3,6,7,10,11-hexaiminotriphenylene)₂ film demonstrates high compactness and uniformity. The root-mean-square roughness of the film is 5.5 nm. The ultraviolet photoelectron spectroscopy and the steady-state photoluminescence spectra exhibit the Ni₃(HITP)₂ film can effectively transfer holes from perovskite film to anode. The perovskite solar cells based on Ni₃(HITP)₂ as a dopant-free hole transport layer achieve a champion power conversion efficiency of 10.3%. This work broadens the application of metal-organic frameworks in the field of perovskite solar cells.