Enhanced Ballistic Transport of Charge Carriers in Alloyed and K-Passivated Alloyed Perovskite Thin Films.

Jooyoung Sung,Akshay Rao,Stuart Macpherson

doi:10.1021/acs.jpclett.0c01548

Jooyoung Sung, Akshay Rao + Show 1 more

Open Access

https://doi.org/10.1021/acs.jpclett.0c01548

Copy DOI

Abstract

Hybrid organic–inorganic perovskites show remarkable charge transport properties despite their deposition via low-temperature solution phase methods. It has recently been shown that this includes the ballistic transport of charges following photoexcitation, with ballistic transport lengths as large as 150 nm measured in MAPI3 films, which is almost twice the value reported for GaAs. Here we explore the ballistic transport regime in high-performance triple-cation and K-passivated triple-cation perovskite films, using femtosecond transient absorption microscopy, which allows us to image carrier motion with 10 fs temporal resolution and 10 nm spatial precision. We observe ballistic transport lengths of 160 and 220 nm in triple-cation and K-passivated triple-cation perovskite films, respectively. We propose that the ballistic transport is limited by nanoscale trap clusters at grain boundaries and interfaces, which can be passivated via chemical treatments to enhance the ballistic transport length, which implies that further enhancements are possible as passivation methods are improved.

Highlights

Hybrid organic−inorganic perovskites show remarkable charge transport properties despite their deposition via low-temperature solution phase methods
While many investigations have focused on steady state or quasi-steady state charge transport properties, it has recently been recognized that hybrid perovskites show unusual nonequilibrium charge transport at early times after light absorption and charge generation
Using a recently developed femtosecond transient absorption microscopy technique, with 10 fs temporal resolution and 10 nm spatial precision, we were able to show that this initial non-equilibrium carrier motion occurs ballistically in MAPI3 films, i.e., before electron−electron scattering takes place, and can transport carriers over a distance of 150 nm in the thin films within 30 fs.[8]

Summary

Introduction

Hybrid organic−inorganic perovskites show remarkable charge transport properties despite their deposition via low-temperature solution phase methods. It is clear that triple-cation films and passivation treatments can enhance optoelectronic performance, but their effect on early time charge transport dynamics has not yet been explored.

Results

Conclusion