Efficient Bifacial Passivation Enables Printable Mesoscopic Perovskite Solar Cells with Improved Photovoltage and Fill Factor

Abstract

Surface defects, which mediate nonradiative recombination, are detrimental to both the photovoltaic performance and stability of perovskite solar cells (PSCs). Improving photovoltage and fill factor (FF) in screen‐printed mesoporous PSCs is a major challenge for approaching the power conversion efficiency (PCE) of the planar configured devices. Herein, a novel bifacial passivation strategy which simultaneously suppresses deep trap states within TiO2 and perovskite through interaction between functional groups and defects is demonstrated for fully printable mesoscopic PSCs. The application of monoethanolamine (MEA) treatment to TiO2 surface not only reduces the energy barrier between TiO2 and perovskite for accelerating the charge transfer but also passivates the uncoordinated Pb defects on the perovskite interface. Due to the synergistic effect of charge extraction promotion and trap passivation, the fabricated PSCs deliver a champion PCE of 15.5% with an enhanced Voc of 0.94 V and FF of 70.4% compared with PSCs without MEA passivation, and the device maintains 97% of its topmost PCE after 240 h under constant simulated solar illumination in air atmosphere. This investigation helps exploit new approaches for defect passivation to further improve both the efficiency and stability of printable mesoscopic PSCs.