Photoluminescence of MAPbI$_3$: a semiconductor science and technology point of view

TL;DR

This study investigates the photoluminescence properties of MAPbI$_3$ thin films across a wide temperature and excitation range, revealing defect-related energy levels, phase-dependent PL behavior, and potential for amplified spontaneous emission, bridging hybrid perovskites with conventional semiconductors.

Contribution

The paper provides a comprehensive systematic analysis of MAPbI$_3$ photoluminescence, including low excitation densities and phase behavior, offering new insights into defect states and emission mechanisms.

Findings

Defect density creates an energy level band in high-quality MAPbI$_3$.

PL intensity ratio varies with temperature and excitation.

Amplified spontaneous emission observed under cw conditions.

Abstract

In this work, we perform steady-state continuous wave (cw) photoluminescence (PL) measurements on a MAPbI$_3$ thin film in the temperature range of 10-160 K, using excitation densities spanning over almost seven orders of magnitude, in particular investigating very low densities, rarely used in the published literature. The temperature range used in this study is below or at the edge of the orthorhombic-tetragonal phase transition in MAPbI$_3$. In particular, we show that even in high quality MAPbI$_3$, capable of providing high photovoltaic efficiency, the defect density is high enough to give rise to an energy level band. Furthermore, we show that the intensity ratio between the two PL components related to the two crystalline phases, is a function of temperature and excitation. At high excitation intensities, we show that amplified spontaneous emission is attainable even in cw conditions. Time-resolved PL is also performed to justify some assignments of the PL features. Finally, our systematic approach, typical for the characterization of semiconductors, suggests that it should also be applied to hybrid halide perovskites and that, under suitable conditions, the PL characteristics of MAPbI$_3$ can be reconciled with those of conventional inorganic semiconductors.