Amorphous-conjugated polymer-additive approach to prepare quality Spiro-OMeTAD-based hole transporting material for efficient Sb2S3 solar cells

Abstract

2,2′,7,7′-Tetrakis-(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) is a common hole transport material (HTM) for efficient solar cells. However, the conventional Spiro-OMeTAD-based HTM contains the bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) additive that often introduces pinholes into the HTM layer to deteriorate device performance. Here, we use amorphous polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) as an additive into the Spiro-OMeTAD-based HTM for efficient Sb2S3 solar cells. It is showed that MEH-PPV remarkably improves the quality of the HTM layer, suppresses the charge recombination and enhances the charge collection efficiency in the Sb2S3 solar cells. With the MEH-PPV additive, the power conversion efficiency of the solar cells is boosted up to 6.02% from the original 5.51% without the additive.