Synthesis of a side-chain hole transporting polymer through Mitsunobu post-functionalization for efficient inverted perovskite solar cells

An efficient post-functionalization protocol of the Mitsunobu reaction between a commercial reactive polymer of poly(4-vinylphenol) (PVP) and 9-(2-hydroxylethyl)-N,N,N,N-tetrakis(4-methoxyphenyl)-9H-carbazole-2,7-diamine is reported to synthesize a novel side-chain polymer (PVP-CZ) with a high density of hole transporting moieties. The polymer PVP-CZ exhibits adequate solvent resistance and excellent film forming ability for the fabrication of inverted perovskite solar cells (PVSCs). The thermal, optical and electrochemical properties of PVP-CZ were investigated in detail. The steady-state photoluminescence (PL) and time resolved photoluminescence (TRPL) decay showed the excellent hole-extracting ability of dopant-free PVP-CZ from the perovskite layer. As a result, the inverted PVSCs delivered a respectable power conversion efficiency of 17.75% with a high fill factor of 81.07%. These results indicate that the synthetic strategy using the post-functionalization of the Mitsunobu reaction is a promising protocol to develop novel side-chain hole transporting polymers for highly efficient PVSCs.