Rational Interface Design and Morphology Control for Blade‐Coating Efficient Flexible Perovskite Solar Cells with a Record Fill Factor of 81%. (25th June 2020) - Wang, Zhen
Abstract: Halide perovskites are one of the ideal photovoltaic materials for constructing flexible solar devices due to relatively high efficiencies for low‐temperature solution‐processed devices. However, the overwhelming majority of flexible perovskite solar cells are produced using spin coating, which represents a major hurdle for upscaling. Here, a scalable approach is reported to fabricate efficient and robust flexible perovskite solar cells on a polymer substrate. Thiourea is introduced into perovskite precursor solution to modulate the crystal growth, resulting in dense and uniform perovskite thin films on rough surfaces. As a decisive step, a cascade energy alignment is realized for the hole extraction layer by rationally designing a bilayer interface comprised of PEDOT:PSS/PTAA with a distinct offset in the highest occupied molecular orbital levels, enabling markedly enhanced charge extraction and spectral response. An efficiency as high as 19.41% and a record fill factor up to 81% are achieved for flexible perovskite devices processed by a scalable printing method. Equally important, the bilayer interface reinforces the bendability of the indium tin oxide substrate, leading to enhanced mechanical robustness of the flexible devices. These results underpin the importance of morphology control and interface design in constructing high‐performance flexible perovskite solar cells. Abstract : Highly efficient flexible perovskite solar cells prepared by blade coating are reported. A dual hole transport layer comprised of "PEDOT:PSS/PTAA" is delicately designed, which forms a cascade energy level alignment, enabling markedly enhanced charge extraction. In conjugation with a morphology control by additive engineering, the scalable coated flexible solar cell shows an impressive efficiency of 19.41% with a record fill factor of 81%.