Affiliation: | 1. Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong;2. Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China;3. Department of Physics, The Chinese University of Hong Kong, Sha Tin, 999077 Hong Kong;4. Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon, 999077 Hong Kong;5. Department of Mechanical Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong |
Abstract: | The crystallographic orientation of polycrystalline perovskites is found to be strongly correlated with their intrinsic properties; therefore, it can be used to effectively enhance the performance of perovskite-based devices. Here, a facile way of manipulating the facet orientation of polycrystalline perovskite films in a controllable manner is reported. By incorporating a cross-linkable organic ligand into the perovskite precursor solution, the crystal orientation disorder can be reduced in the resultant perovskite films to exhibit the prominent (001) orientation with a preferred stacking mode. Moreover, the as-formed low-dimensional perovskites (LDPs) between the organic ligand and the excess lead iodide can passivate the defects around the grain boundaries. Consequently, highly efficient p-i-n structured perovskite solar cells (PSCs) can be made in both rigid and flexible forms from modified perovskites to show high power conversion efficiencies (PCE) of 24.12% and 23.23%, respectively. The devices also exhibit superior long-term stability in a humid environment (with T90 > 1000 h) and under thermal stress (retaining 87% of its initial PCE after 1000 h). More importantly, the ligand enables the derived LDPs to be crosslinked (under 254 nm UV illumination) to demonstrate excellent mechanical bending durability in flexible devices. |