Metal halide perovskites (MHPs) have rapidly emerged as leading contenders in photovoltaic technology and other optoelectronic applications owing to their outstanding optoelectronic properties. After a decade of intense research, an in-depth understanding of the charge carrier transport in MHPs is still an active topic of debate. In this Perspective, we discuss the current state of the field by summarizing the most extensively studied carrier transport mechanisms, such as electron–phonon scattering limited dynamics, ferroelectric effects, Rashba-type band splitting, and polaronic transport. We further extensively discuss the emerging experimental and computational evidence for dominant polaronic carrier dynamics in MHPs. Focusing on both small and large polarons, we explore the fundamental aspects of their motion through the lattice, protecting the photogenerated charge carriers from the recombination process. Finally, we outline different physical and chemical approaches considered recently to study and exploit the polaron transport in MHPs.

On a macroscopic level both injection (CPGE) and shift (LPGE) currents can be linked to secondorder optical nonlinear effects, as

We investigate the possible formation of polarons in four organic perovskites (CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, and CH3NH3PbI2Cl1) using a density functional theory (DFT) calculations with local potentials and hybrid functionals. We show that DFT+U method with U = 8 eV predicts a correct band-gap and matches the forces on ions from hybrid calculations. We then use the DFT + U approach to study the effect of polarons, i.e. to search the configuration space and locate the lowest energy localized band gap state self-trapped hole (STH). STH configurations were found for three pure halides and one mixed halide system. Spin orbit coupling (SOC) was also taken into account and the results may be found in the supplementary material. This study focuses on the +U method; however, SOC corrections added to the DFT+U calculations also resulted in STH states in all four systems.

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This paper assesses the interface stability of the perovskite CsPbBr3 and transport layer CuI using density functional theory and band offset calculations. As a low-cost, more stable alternative to current hole transport materials, CuI may be used to template the epitaxial growth of perovskites such as CsPbBr3 owing to a 1% lattice constant mismatch and larger bulk modulus. We compare all eight atomic terminations of the interfaces between the (100) low-energy facet for both CsPbBr3 and CuI, increasing material thickness to consider charge density redistribution and bonding characteristics between surface and bulk-like regions. A low energy atomic termination is found to exist between these materials where alternating charge accumulation and depletion regions stabilize bonds at the interface. Band offset calculations reveal a type I straddling gap offset in the bulk shifting to a type II staggered gap offset as the thickness of the materials is increased, where the built-in potential changes as layer thickness increases, indicating the tunability of charge separation at the interface. CuI may, thus, be used as an alternative hole transport layer material in CsPbBr3 optoelectronic devices.