Helen Park4,6,Eunyoung Choi1,2,3,Jin-Won Lee4,Jae Sung Yun5,3
Diamond Light Source1,University of Cambridge2,University of New South Wales3,Korea Research Institute of Chemical Technology (KRICT)4,University of Surrey5,University of Science and Technology (UST)6
Helen Park4,6,Eunyoung Choi1,2,3,Jin-Won Lee4,Jae Sung Yun5,3
Diamond Light Source1,University of Cambridge2,University of New South Wales3,Korea Research Institute of Chemical Technology (KRICT)4,University of Surrey5,University of Science and Technology (UST)6
Although long-chain organic halide salts have been effectively used in three-dimensional (3D) perovskite-based solar cells for surface passivation, it has been reported that unexpected halide defects could be formed from the organic halide salts and the solvents used for dissolving the organic halide salts, which results in degradation of the devices. In this work, aluminium oxide (AlO<i><sub>x</sub></i>) via atomic layer deposition (ALD) was introduced onto octylammonium iodide (OAI) on the perovskite layer to suppress the generation of undesired defects while still obtaining the benefits of organic halide salts. The devices incorporating AlO<i><sub>x</sub></i> on OAI-treated perovskites (OAI/AlO<i><sub>x</sub></i>) show enhancement in both device performance and photostability compared to devices with only OAI surface passivation. Diffusion of aluminium from AlO<i><sub>x</sub></i> into the perovskite is observed from surface characterization. Photo-generated carrier transport in both the surface and bulk of the perovskite absorber is investigated by wavelength-dependent surface photovoltage microscopy, and grazing-incidence-wide-angle X-ray scattering was utilized to investigate the crystallinity changes of the perovskite under prolonged illumination. The effects of the inorganic oxide layer on the stability and performance of organic halide salt-treated devices will be addressed, and the mechanisms involved in the enhanced performance and stability will also be discussed.