Surface Engineering of Low-Temperature 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 high-temperature 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 low-temperature 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.