Description
Lead-halide perovskites have shown promise as one of the leading materials in emergent photovoltaic technology design. Power conversion efficiencies close to 20% were achieved over a decade ago with single-junction perovskite solar cells (PSCs), and today efficiencies above 30% are seen in a wide variety of tandem cell architectures. One key advantage of these materials is the optoelectronic tunability provided by swapping the chemical compositions of cation and anion components. Using binary mixtures of different halides can provide even finer control of band gaps and the high configurational entropy of certain mixing ratios can improve thermodynamic stability. Experimental observations have however revealed the tendency for phase segregation into unmixed regions upon exposure to light, limiting practicality for PSC usage. Halide vacancies are believed to be the cause, but the exact microscopic origins of this photo-induced instability are most accessible through first-principles atomistic modelling, revealing dynamic ion behaviour while keeping close control of material parameters. For the inorganic I-Br perovskite alloy CsPbI2Br, transition state theory methods with density functional theory (DFT) calculations were used to determine energy barriers and diffusion constants for ion migration pathways mediated by intrinsic halide defects, for various structural phases and defect charge states. These simulations provide insight into the role that temperature and compositional disorder play on ion diffusion dynamics, leading to better understanding of how to optimise the performance and stability of mixed-composition PSCs.
| I am the presenting author | Yes |
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