The application of methylammonium (MA) lead halide perovskites, CH 3 NH 3 PbX 3 (X = I, Br, Cl), in perovskite solar cells has made great recent progress in performance efficiency during recent years. However, the rapid decomposition of these materials in humid environments hinders outdoor application, and thus, a comprehensive understanding of the degradation mechanism is required. We investigate the effect of water intercalation and hydration of the decomposition and ion migration of CH 3 NH 3 PbX 3 using first-principles calculations. We find that water interacts with PbX 6 and MA through hydrogen bonding, and the former interaction increases gradually, while the latter hardly changes when going from X = I to Br and to Cl. Thermodynamic calculations indicate that water exothermically intercalates into the perovskite, and suggest that the water intercalated and monohydrated compounds are stable with respect to decomposition. More importantly, the water intercalation reduces the activation energies for vacancy-mediated ion migration, which become higher going from X = I to Br and to Cl. Our work indicates that hydration of halide perovskites must be avoided to prevent the degradation of solar cells upon moisture exposure.
Bibliographical noteFunding Information:
This work was supported partially by the State Committee of Science and Technology, Democratic People's Republic of Korea, under the state project “Design of Innovative Functional Materials for Energy and Environmental Application” (No. 2016-20). The research in the UK was supported by the Royal Society and the Leverhulme Trust, and the Imperial College High Performance Computing Service. A. P. M. was supported by a studentship from the Centre for Doctoral Training in Theory and Simulation of Materials at Imperial College London, funded by the EPSRC under grant no. EP/G036888. The calculations have been carried out on the HP Blade System C7000 (HP BL460c) that is owned and managed by Faculty of Materials Science, Kim Il Sung University. P. R. F. B. was supported by EPSRC grant no. EP/M025020/1 and EP/P02484X/1.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)