Two-dimensional Halide Perovskites: Tuning Electronic Activities of Defects

TL;DR

This paper explores how the electronic activities of defects in 2D halide perovskites can be tuned through synthesis conditions, revealing their potential for improved nano-electronic and optoelectronic applications.

Contribution

It demonstrates the tunability of defect electronic activities in 2D halide perovskites, contrasting with other 2D semiconductors, and explains the underlying ionic bonding effects.

Findings

Defects in 2D perovskites are highly tunable via synthesis conditions.

Certain defects can be converted from active to inactive without deep gap states.

Enhanced ionic bonding influences defect formation energies and activities.

Abstract

Two-dimensional (2D) halide perovskites are emerging as promising candidates for nano-electronics and optoelectronics. To realize their full potential, it is important to understand the role of those defects that can strongly impact material properties. In contrast to other popular 2D semiconductors (e.g. transition metal dichalcogenides MX2) for which defects typically induce harmful traps, we show that the electronic activities of defects in 2D perovskites are significantly tunable. For example, even with a fixed lattice orientation, one can change the synthesis conditions to convert a line defect (edge or grain boundary) from electron acceptor to inactive site without deep gap states. We show that this difference originates from the enhanced ionic bonding in these perovskites compared with MX2. The donors tend to have high formation energies, and the harmful defects are difficult to form at a low halide chemical potential. Thus we unveil unique properties of defects in 2D perovskites and suggest practical routes to improve them.