Low Temperature Atomic Layer Deposited TiO2 Compact Layers for Planar Perovskite Solar Cells

Abstract

Titanium dioxide (TiO2) thin films have been utilized in a wide range of applications in optoelectronics and solar energy conversion. In particular, TiO2 has been exclusively used in photovoltaic devices and photoelectrochemical cells owing to its ability to efficiently transport electrons and passivate photoactive materials against aqueous media. However, TiO2 exhibits optimal transport properties in the crystalline anatase phase, and thus requires a high temperature annealing, which significantly limits its application in temperature sensitive substrates or active materials (e.g. organic-inorganic hybrid perovskites). Moreover, while high resistance of TiO2 films necessitates the need for ultrathin films to reduce series resistance in PV devices, the synthesis of ultrathin pinhole-free TiO2 films remains a challenge through conventional deposition methods. To address these issues, TiO2 compact layers for planar perovskite PV devices were deposited via atomic layer deposition (ALD) – a chemically diverse vapor phase deposition technique with the capability to synthesize ultrathin pinhole-free films.