Atomic Layer Deposited TiO2-IrOx Alloy as a Hole Transport Material for Perovskite Solar Cells

The hole transport layer (HTL) is one of the key components in planar perovskite solar cells. This study reports a new kind of HTL fabricated using atomic layer deposition (ALD). By alloying TiO2 with IrOx, it is demonstrated that TiO2, a well-known electron-selective contact and electron transport layer in photovoltaic devices, can behave as an HTL with an appropriately high work function. Perovskite Cs(0.17)FA(0.83)Pb(I0.83Br0.17)(3) solar cells including this new hole transport material achieve a power conversion efficiency of 15.8% under AM1.5G simulated solar irradiation compared to a 14.3% efficiency for otherwise-identical devices incorporating a more standard NiO HTL layer. These results suggest the promise of transition metal oxide alloys synthesized by ALD as hole contact materials for optoelectronic devices, including advanced photovoltaics.