A simple and dopant-free hole-transporting material based on (2-ethylhexyl)-9H-carbazole for efficient planar perovskite solar cells

A hole-transporting material (HTM) based on (2-ethylhexyl)-9H-carbazole as the core and N,N-di-p-methoxyphenylamine as the end group (CMO) has been designed. CMO with a simple structure can be synthesized by a one-step process in a high yield and it shows good solubility in solvents. Steady-state and time-resolved photoluminescence measurements show that CMO has significant charge extraction ability. Planar perovskite solar cells (pero-SCs) based on CMO as the HTM showed a high power conversion efficiency of 15.92%. For reference purposes, pero-SCs based on 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9-9′-spirobifluorene (Spiro-OMeTAD) were fabricated and a PCE of 16.70% was reached. CMO is one of the simplest HTM materials reported, which shows a PCE comparable to that of Spiro-OMeTAD at the same time.