"Crystallization Engineering for Improved Performance in Perovskite Photovoltaics"
Crystallization Engineering for Improved Performance in Perovskite Photovoltaics
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Despite rapid advances in power conversion efficiencies, current perovskite solar cells still suffer from severe degradation under normal operating conditions. Two-dimensional (2D) perovskites have emerged to alleviate this issue, but are prone to having reduced performances due to the unfavorable alignment of the crystal grains parallel to the substrate. While certain fabrication steps, such the addition of methylammonium chloride (MACl), can induce a more advantageous vertical orientation, the mechanisms behind this process remain unclear. This work demonstrates the transition to the vertically aligned crystal grains by incorporating MACl into solar cells based on the perovskite layer containing the organic cation 3-fluorobenzylammonium (3FBA). Examination of the partially crystallized perovskite films reveals the likely cause of the preferential orientation to be the nucleation at the liquid-air interface. The investigated solar cells reach champion power conversion efficiencies (PCEs) of 18.5%, with short-circuit current densities of up to 24.6 mAcm (-2) and an average PCE of 14.6+/-1.4%. In addition, the devices display improved stability to environmental oxygen and moisture compared to their 3D counterparts, retaining more than 80% of their initial efficiency for 43 days despite a high atmospheric humidity of 60+/-10% RH.