Organic hole-transporting materials for efficient perovskite solar cells

Nowadays hole-transporting materials based on conductive small organic molecules and polymers have become the hottest topic in high-performance perovskite solar cells. Currently, the perovskite solar cells have reached certified power conversion efficiency of 22.1%. 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene and poly-triarylamine are the two widely used hole-transporting materials in highly efficient perovskite solar cells. It is highly desirable to seek other low-cost and efficient hole-transporting material for highly efficient and stable perovskite solar cells. This review summarizes recent progress of typical small molecules, conductive polymer hole-transporting materials used for efficient perovskite solar cells. Particularly, we focus on those hole transporting material based on triphenylamine units.