A facilely synthesized ‘spiro’ hole-transporting material based on spiro[3.3]heptane-2,6-dispirofluorene for efficient planar perovskite solar cells

A low-cost spiro[3.3]heptane-2,6-dispirofluorene (SDF) based hole transporting material termed SDF-OMeTAD has been designed and synthesized via a two-step reaction, representing a considerable simplification with respect to that of the well-known spiro-OMeTAD. The SDF-OMeTAD was exploited in lead halide planar perovskite solar cells using low-temperature solution-processed SnO2 as the electron transporting layer, delivering a competitive power conversion efficiency of 13.01% with an open-circuit voltage of 1.10 V under 100 mW cm−2 AM 1.5G solar illumination. The facile synthesis approach of SDF-OMeTAD from commercially available starting materials will facilitate SDF-based molecules to be further exploited in thin film organic–inorganic perovskite solar cells and can be optimized to further enhance power conversion efficiency.