Surface Engineering of Lowerature Processed Mesoporous TiO₂ via Oxygen Plasma for Flexible Perovskite Solar Cells

A major problem in the application of mesoporous TiO₂ as an electron transport layer for flexible perovskite solar cells is that a higherature sintering process is required to remove organic additives from the TiO₂ layer. A facile oxygen plasma process is herein demonstrated to fabricate mesoporous-structured perovskite solar cells with significant photovoltaic performance at low temperatures. When the lowerature processed TiO₂ layer is modified via oxygen plasma, the organic additives in the TiO₂ layer that hinder the charge transport process are successfully decomposed. The oxygen plasma treatment improves the wettability and infiltration of the perovskite layer and also passivates the oxygen vacancy related traps in TiO₂. Hence, the oxygen plasma treatment evidently enhances charge extraction and transport, thereby improving photovoltaic performance and decreasing hysteresis.