Star-shaped molecule with planar triazine core and perylene diimide branches as an n-type additive for bulk-heterojunction perovskite solar cells

Abstract

A novel star-shaped molecule, TPDI, featuring a triazine unit as the core and units of a perylene diimide derivative as its conjugated branches, has been synthesized for application as an n-type additive in methylammonium lead iodide (CH3NH3PbI3, MAPbI3)–based bulk-heterojunction perovskite solar cells (PVSCs). The architecture of the PVSCs was indium tin oxide/poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate)/MAPbI3:TPDI/[6,6]-phenyl-C61-butyric acid methyl ester/Ag. The star-shaped molecule TPDI was added into the MAPbI3 layer to minimize grain boundary defects and enhance the coverage and crystal grain sizes of the perovskite film. Upon the incorporation of a suitable amount of TPDI, the defects of the perovskite crystals were compensated for, and the absorbance and electron-transfer ability of the photoactive active layer were enhanced, thereby improving the photovoltaic performance of the PVSC. An open-circuit voltage of 0.83 V, a short-circuit current of 19.2 mA cm−2, a fill factor of 0.68, and a photoconversion efficiency of 10.84% were obtained for the TPDI-doped PVSC.