Novel dopant-free hole-transporting materials for efficient perovskite solar cells

Two novel highly conjugated small organic molecules as hole transporting materials (HTMs) coded T(EDOT-TPA)₂ and DBT(QT-TPA)₂ were designed and developed by utilizing facile synthetic procedures with high yields. The fabricated perovskite solar cells (PSCs) utilizing these HTMs without any dopants under 1 sun illumination (100 mW cm⁻², AM 1.5G) and surface area of 1.02 cm² achieved a short circuit current (J_SC = 19.23), open circuit voltage (V_OC = 1.042), fill factor (FF = 0.679) and overall power conversion efficiency (PCE = 13.61%) for DBT(QT-TPA)₂. While, T(EDOT-TPA)₂ exhibited (J_SC = 20.25, V_OC = 1.04, FF = 0.583, and PCE = 12.27%). These dopant free HTM based PSCs achieved superior PCEs compared to that of undoped Spiro-OMeTAD (PCE = 9.34%) based PSCs and a comparable photovoltaic performance to the PSCs using doped Spiro-OMeTAD (J_SC = 20.37, V_OC = 1.057, FF = 0.74, and PCE = 15.93) as the HTM under same fabrication conditions. Noticeably, the absence of additives is of significant importance, as DBT(QT-TPA)₂ and T(EDOT-TPA)₂ based PSCs still produces a J_sc up to 20.25 mA cm⁻² and a comparable PCE of 13.61%, which reduces the fabrication cost of cm sized PSCs.