First Principle Modeling of Hybrid Halide Perovskites for Optoelectronic Applications
Halide perovskites (HP) are a promising material for use in solar cells and electronic devices, offering a comparable, less expensive alternative to current technologies. Devices with impressive optical and electronic properties are being made in the lab, but a robust theoretical understanding on the underlying photophysics in HPs is required to improve current devices and predict future devices. The causes for positive device behaviors like long charge carrier lifetimes and long diffusion lengths, and high carrier mobility as well as detrimental device behavior like degradation and instability are both topics of debate and may be studied from first principle using modern, state-of-the-art computational software and high-power computing clusters. In this work, HP materials are studied using ab-initio methods to study the ground state and excited state properties. A model used in oxide perovskites is shown to work well in HPs to model polaronic properties, as these materials exhibit ionic bonding and therefore are predicted to exhibit strong electron-phonon coupling. Relativistic effects are studied using spin orbit coupling (SOC) corrections to account for large atoms like Pb and I. The Rashba effect is seen when SOC corrections are added which implies inversion symmetry breaking and momentum dependent photoexcitation, both of which were confirmed in experiments done by our collaborators. The strength and effect of SOC on mixed metal and mixed halide perovskites shows that the benchmark HP CH3NH3PbI3 (MAPI) has the largest splitting, indicating promising potential for applications in ultrafast optical detectors, while other mixed HPs may be used as spin-injection and transport materials. Finally, the band offset method for studying interfaces revealed the lowest energy face between the HP CsPbBr¬3 and CuI to be the PbBr2 on Cu interface, where a type II band offset indicates charge separation at the interface; CuI is predicted to be a viable, low cost, alternative charge transport material for HP devices. HPs have already excited the solar cell community with the promise of affordable alternatives that will be cheaper than the current fossil fuels causing anthropogenic climate change and have the chance to create the same fervor in other semiconductor arenas as research continues to improve our understanding.
Solar cell, LED, Perovskite, Halide, Optoelectronics, Electronics, Density functional theory, First principle
Welch, E. (2019). <i>First principle modeling of hybrid halide perovskites for optoelectronic applications</i> (Unpublished dissertation). Texas State University, San Marcos, Texas.