Deciphering the Effect of Traps on Electronic Charge Transport Properties of Methylammonium Lead Tribromide

TL;DR

This study investigates how traps affect charge transport in methylammonium lead tribromide, revealing multiple trap states, strong detrapping activity, and their impact on device mobility, using combined spectroscopy and simulation methods.

Contribution

It introduces a new model for effective mobility considering multiple traps and provides detailed insights into trap dynamics in MAPbBr3.

Findings

Identified three energy trap states in MAPbBr3.

Discovered strong detrapping activity contrary to previous studies.

Showed traps significantly influence mobility and device performance.

Abstract

Organometallic halide perovskites (OMHPs) have undergone remarkable developments as highly efficient optoelectronic materials for a variety of applications. Several studies indicated the critical role of defects on the performance of OMHP devices. Yet, the parameters of defects and their interplay with free charge carriers remain unclear. In this study we explore the dynamics of free holes in methylammonium lead tribromide (MAPbBr3) single crystals using the time of flight (ToF) current spectroscopy. By combining the current waveform (CWF) ToF spectroscopy and the Monte Carlo (MC) simulation, three energy states were detected in the band gap of MAPbBr3. Additionally, we found the trapping and detrapping rates of free holes ranging from a few us to hundreds of us and, contrary to previous studies, a strong detrapping activity was revealed. It was shown that these traps have a significant impact on the transport properties of MAPbBr3 single crystal devices, including drift mobility and mobility-lifetime product. To demonstrate the impact of traps on the delay of free carriers, we developed a new model of the effective mobility valid for the case of multiple traps in a semiconductor. Our results provide a new insight on charge transport properties of OMHP semiconductors, which is required for further development of this class of optoelectronic devices.