Highly mobile hot holes in Cs2AgBiBr6 double perovskite

Abstract

Highly mobile hot charge carriers are a prerequisite for efficient hot carrier optoelectronics requiring long-range hot carrier transport. However, hot carriers are typically much less mobile than cold ones because of carrierphonon scattering. Here, we report enhanced hot carrier mobility in Cs2AgBiBr6 double perovskite. Following photoexcitation, hot carriers generated with excess energy exhibit boosted mobility, reaching an up to fourfold enhancement compared to cold carriers and a long-range hot carrier transport length beyond 200 nm. By optical pump-infrared push-terahertz probe spectroscopy and frequency-resolved photoconductivity measurements, we provide evidence that the conductivity enhancement originates primarily from hot holes with reduced momentum scattering. We rationalize our observation by considering (quasi-)ballistic transport of thermalized hot holes with energies above an energetic threshold in Cs2AgBiBr6. Our findings render Cs2AgBiBr6 as a fascinating platform for studying the fundamentals of hot carrier transport and its exploitation toward hot carrier-based optoelectronic devices.