Phenoxazine‐benzimidazolium ionic hole transport material for perovskite solar cells

Abstract A novel organic ionic material, hole transport material‐1 (HTM‐I) , was synthesized and characterized as a hole transport material for perovskite solar cells (PSCs), with the aim of replacing 2,2',7,7'‐Tetrakis[N,N‐di(4‐methoxyphenyl)amino]‐9,9'‐spirobifluorene (Spiro‐OMeTAD). HTM‐I was designed to incorporate both phenoxazine and benzimidazolium iodide salt structures, and its chemical structure was confirmed using 1 H NMR and high‐resolution mass spectrometry. Differential scanning calorimetry measurements revealed that HTM‐I maintained an amorphous phase throughout the temperature range of −60 – 200 °C, and thermogravimetric analysis showed good thermal stability up to 220 °C. To evaluate its potential as a hole transport layer, perovskite solar cells were fabricated using a fluorine‐doped tin oxide (FTO)/compact‐TiO 2 /(Cs/FA/MA)Pb(I/Br) 3 /hole transport layer/Au configuration. The resulting n–i–p planar structure exhibited a power conversion efficiency of 10.4%.