Morphological control of organic-inorganic perovskite layers by hot isostatic pressing for efficient planar solar cells

Morphological control of organic-inorganic perovskite layers is crucial for efficient planar solar cells. In this study, we show that hot isostatic pressing (HIP) of perovskite layers using a pressure of 200 MPa in 90°C water is very effective for improving the perovskite film morphology. After HIP treatment, undesirable pin holes and spatial gaps between crystals in the perovskite layers were significantly reduced. Improved crystallinity and enhanced diffusion lengths for both electrons and holes were also confirmed in the HIP-treated perovskite layers. Solar cells containing the perovskite layers as light absorbers were fabricated and characterized under simulated solar light (AM1.5G, 100 mW cm^-2). The HIP treatment induced a marked enhancement of short-circuit current density, open-circuit voltage, fill factor, and power conversion efficiency because of the improved morphology and crystallinity and enhanced carrier diffusion. The HIP-treated solar cells achieved efficiencies of 10.6 ± 0.7%, which are about 1.5 times higher than those of the untreated solar cells (7.20 ± 0.59%).