Phase Transition Control for High-Performance Blade-Coated Perovskite Solar Cells

Abstract

Here, we have identified that the key issue for rational transitioning from spin-coating to blade-coating processes of perovskite films arises from whether intermediate phases participate in the phase transition. In situ characterizations were carried out to provide a comprehensive picture of structural evolution and crystal growth mechanisms. These findings present opportunities for designing an effective process for blade-coating perovskite film: a large-grained dense perovskite film with high crystal quality and photophysical properties can be obtained only via direct crystallization for both spin-coating and blade-coating processes. As a result, the blade-coated MAPbI3 films deliver excellent charge-collection efficiency at both short circuit and open circuit, and photovoltaic properties with efficiencies of 18.74% (0.09 cm2) and 17.06% (1 cm2) in planar solar cells. The significant advances in understanding how the phase transition links spin-coating and blade-coating processes should provide a path toward high-performance printed perovskite devices. Hybrid organic-inorganic perovskite (HOIP) solar cells have recently emerged as a highly promising and inexpensive solution for sustainable energy. Simple and scalable fabrication is a vibrant prospect to be exploited further for perovskite solar cells. However, understanding and control over the phase transition including structural evolution and crystal growth mechanisms are missing when moving a spin-coating to a printing process. We utilize in situ diagnostics, including synchrotron-based grazing-incidence X-ray diffraction and optical microscopy, to investigate MAPbI3 phase transition during both spin-coating and blade-coating processes. We propose direct crystallization via skipping intermediate phases as a key issue for a rational transfer from spin-coating to blade-coating processes. We thus demonstrate an effective process for high-quality blade-coated films, which deliver high efficiencies of 18.74% (0.09 cm2) and 17.06% (1 cm2) in planar perovskite solar cells. Hybrid organic-inorganic perovskite solar cells have recently emerged as a highly promising and inexpensive solution for sustainable energy. However, a full comprehensive picture of the phase transition including structural evolution and crystal growth mechanisms is missing for both scalable printing and lab-based spin-coating processes. Here we reveal fundamental insights into the perovskite phase transition when moving between spin-coating and printing processes, providing a rational path toward optimization of printed devices.