Sputter-deposited TiOx thin film as a buried interface modification layer for efficient and stable perovskite solar cells

Despite perovskite solar cells (PSCs) based on a SnO 2 hole-blocking layer (HBL) are achieving excellent performance, the non-perfect buried interface between the SnO 2 HBL and the perovskite layer is still an obstacle in achieving further improvement in power conversion efficiency (PCE) and stability. The poor morphology with numerous defects and the energy level mismatch at the buried interface constrain the open circuit voltage and cause instability. Herein, a sputter-deposited TiO x thin film is used as a buried interface modification layer to address the aforementioned issues. Utilizing in situ grazing-incidence small-angle X-ray scattering (GISAXS) during the sputter deposition, we monitor and unveil the growth process of the TiO x thin film, identifying a 10 nm thickness optimum. The defects at the buried interface are passivated through tuning the growth, leading to a suppressed non-radiative recombination and improved PCE (from 22.19 to 23.93%). The evolution of the device performance and the degradation process of PSCs using operando grazing-incidence wide-angle X-ray scattering (GIWAXS) under the protocol ISOS-L-1I explains the enhanced stability introduced by the buried interface modification via a sputter-deposited TiO x thin layer. The perovskite decomposition process and the detrimental formation of PbI 2 are both slowed down by the TiO x thin layer. A sputter-deposited TiO x thin layer as a buried interface modification layer is optimized with an in situ scattering study during sputter deposition, resulting in improved photovoltaic performance and operational stability of perovskite solar cells by improving buried interface quality and slowing down the perovskite degradation as seen in operando scattering studies. • The Stranski-Krastanov growth mechanism of sputter deposited TiO x thin film is clarified by in situ GISAXS. • TiO x buried interface modification layer enhance the interface contact quality and reduce the nonradiative recombination at the interface. • The PCE is improved from 22.19 to 23.93% after buried interface modification with sputter deposited TiO x . • The operando GIWAXS measurement verify the higher stability of buried interface modification device.