An effective TiO2 blocking layer for hole-conductor-free perovskite solar cells based on carbon counter electrode

The hole-transporting materials and noble metal employed in normal perovskite solar cells (PSCs) limited their practical application. In this work, the high photovoltaic performance hole-conductor-free PSCs based on carbon counter electrode were fabricated in air atmosphere with high humidity condition (HR) around 55%. An efficient TiO2 blocking layers (BL-TiO2) was prepared by spin-coating the precursor solutions containing ethanol (CH3CH2OH), titanium n-butoxide (Ti(OC4H9)4) and diethanolamine (C4H11NO2 DEA) with different molar ratios (CH3CH2OH: Ti(OC4H9)4: DEA = 30: 1: x) on TiCl4 per-treated FTO glass. When adding DEA in Ti precursor solution, it would revamp the cracks of blocking layer, the suitable alkaline environment provided by DEA can contribute to growing compact BL-TiO2. Electrical impedance measurements were performed to investigate the kinetic issues of charging transport performance in PSCs with different amount of DEA. The optimized PSCs exhibited a short-circuit photocurrent density of 22.71 mA/cm2, open-circuit voltage of 954 mV, fill factor of 0.55 and power conversion efficiency (PCE) of 11.92% when DEA molar ratios x = 0.75. The PCE of optimized PSCs retained about 90% after 21 days in air with HR around 55%. The low cost and outstanding properties endow the present carbon counter electrode based PSCs with immense application potentials.