Learning about the Structural Dynamics of Semiconductor Perovskites from Electron Solvation Dynamics

Semiconductors of the perovskite form have attracted considerable attention in recent years, most notably for their performance in photovoltaics. One key puzzle was how a disordered film could support such performance. A number of investigations have led to a current picture of defect tolerance due to a soft, ionic lattice giving rise to dynamic disorder. Moreover, the presence of polarons may be connected to this defect tolerance and ultimately in the device performance, whether photovoltaics or light emitting diodes. How do these ionic semiconductors relate to their covalent cousins, for which defect-free perfection is a main goal? In this Perspective, the question of ionicity as it gives rise to glassy structural dynamics is considered. How do these glassy structural dynamics control the optical response and thus the optoelectronic properties of the system? The recent literature is reviewed with a focus on ultrafast structural dynamics. Highlighted in the discussion of the structure/function relation is our recent work which maps the chronology of events from electronic coherence to photon emission using a suite of three time-resolved spectroscopies: twodimensional electronic spectroscopy, state-resolved pump/probe spectroscopy, and time-resolved photoluminescence spectroscopy. These works collectively advance our understanding of liquid-solid duality in these defect-tolerant ionic semiconductors. With the connection to liquid-like dynamics made, a brief discussion of ultrafast solvation dynamics is presented. The specific connection between excess charges in liquids and solids can be found in the solvated electron, which once again serves as a prototype for electronic structure and dynamics in the condensed phase. We hope that finding isomorphisms between phases can provide insight into these new materials.

Automated summary

Semiconductors with perovskite structures have shown promising performance in photovoltaics, with defect tolerance being a key focus. The ionic lattice of these semiconductors leads to dynamic disorder, potentially connected to the presence of polarons and impacting device performance. Understanding the glassy structural dynamics and their control over optical response is crucial for advancing optoelectronic properties in these materials.