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

Graphical abstract showing the photovoltaic performance of the fabricated perovskite solar cells with the dopant free T(EDOT-TPA) 2 and DBT(QT-TPA) 2 . • Two novel HTMs T(EDOT-TPA) 2 and DBT(QT-TPA) 2 have been synthesized and characterized for perovskite solar cells. • A maximum PCE of 13.61% achieved for the dopant-free DBT(QT-TPA) 2 based device. • These HTMs outperformed the dopant-free Spiro-OMeTAD-based device (PCE = 9.34%) under the same conditions. • These HTMs are a promising candidate to replace the commercial Spiro-OMeTAD. 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 cm 2 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.