Ambient environment induced synergetic improvement in morphology and iodine vacancy passivation by MAI surface engineering in mixed-cation lead mixed-halide (FA0.85MA0.15PbI0.55Br0.45) perovskite solar cells

• Published in: Surfaces and interfaces Vol. 29; p. 101703
• Main Authors: Srivastava, Ravi P., Lee, Jia, Khang, Dahl-Young
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-04-2022
• Subjects: Life-time; Passivation; Perovskite solar cells; Recombination; Trap-states; Recombination; Trap-states; Perovskite solar cells; Passivation; Life-time
• ISSN: 2468-0230; 2468-0230
• DOI: 10.1016/j.surfin.2021.101703

Perovskite solar cells (PSCs), have made tremendous progress but are still far away from theoretically estimated power conversion efficiencies (PCEs) and commercialization. Defects present in the perovskite materials and at various interfaces (between ETL/HTL and perovskite) in devices are inhibiting the performance to get closer to the theoretical limits, whereas the controlled atmosphere fabrication is creating a bottleneck in large scale production. Therefore, meticulous attention is required to overcome these problems. In this work, we report a very simple, facile and efficient post-synthesis surface treatment with methyl ammonium iodide (MAI) for surface and grain boundary defect passivation in the PSCs processed in fully ambient atmosphere. Ambient atmosphere, MAI surface treatment showed synergetic improvement, firstly it healed the defects (iodine trap states) existing on the surface/interface and grain boundaries and secondly increased the grain size, thereby reducing the defect sites. The improved crystallinity, morphology and decreased defects, reduced the trap density and non-radiative recombination losses leading to fast charge extraction. As a result, planar (n-i-p) PSCs, passivated with optimum MAI concentration, showed significantly higher boost (14%) in the power conversion efficiency (PCE) compared to previous MAI surface treatments, where no morphological changes were observed.