Sol-Gel Prepared Spinel HTLs for Assembling 20% Efficiency Perovskite Solar Cell in Air Without Using Anti-Solvent and Toxic Solvent.

Low-temperature sol-gel prepared ZnCo 2 O 4 spinel-based thin films are developed as high-performance hole transporting layer (HTL) for coating perovskite film (NA-Psk) from the basic MAPbI 3 /ACN/CH 3 NH 2 solution in air without using anti-solvent. Inverted PSC based on 2 mole% (vs Zn) Cu 2+ doped ZnCo 2 O 4 (2%Cu@ZnCo 2 O 4 ) HTL and NA-Psk absorber exhibit the maximum power conversion efficiency (PCE) of 20.0% with no current hysteresis while the cell based on ZnCo 2 O 4 and PEDOT:PSS HTL (using NA-Psk absorber) achieves the PCE of 15.79% and 12.3% with a current hysteresis index of 9.8% and 32.4%, respectively. Without encapsulation, PSCs based on 2%Cu@ZnCo 2 O 4 , ZnCo 2 O 4 , and PEDOT:PSS HTLs maintain 90%, 77%, and 12%, respectively of the original efficiency by standing in ambient atmosphere (temperature: 20-25 °C, RH:30%-40%) for 1800 h. Large area (10 cm × 10 cm substrate) perovskite mini-module (PSM) with PCE over 15% is also demonstrated by using sol-gel prepared 2%Cu@ZnCo 2 O 4 HTL. The poor photovoltaic performance of PEDOT:PSS HTL is due to the basic MAPbI 3 /ACN/CH 3 NH 2 solution will deprotonate the acidic PEDOT:PSS to reduce its conductivity whereas ZnCo 2 O 4 HTL are not affected by basic perovskite precursor solution.