Visualization of carrier transport in lateral metal-perovskite-metal structures and its influence on device operation

TL;DR

This study investigates carrier transport mechanisms at metal-perovskite interfaces in lateral devices, revealing how inter-electrode length and bias influence device regimes, with implications for optimizing perovskite photodetectors.

Contribution

It provides detailed insights into carrier dynamics and transport barriers at metal-perovskite interfaces, using advanced microscopy techniques to link device structure with performance.

Findings

Distinct ohmic and SCLC regimes controlled by electrode length and bias

Minimal ion-screening effects observed at the interface

High responsivity and fast response time achieved in short-channel devices

Abstract

The high performance of hybrid perovskite based devices is attributed to its excellent bulk-transport properties. However, carrier dynamics, especially at the metal-perovskite interface, and its influence on device operation are not widely understood. This work presents the dominant transport mechanisms in methylammonium lead iodide (MAPbI3) perovskite-based asymmetric metal-electrode lateral devices. The device operation is studied with inter-electrode lengths varying from 4 {\mu}m to 120 {\mu}m. Device characteristics indicate distinct ohmic and space-charge limited current (SCLC) regimes that are controlled by the inter-electrode length and applied bias. The electric-potential mapping using Kelvin-Probe microscopy across the device indicates minimal ion-screening effects and the presence of a transport barrier at the metal-MAPbI3 junction. Further, photocurrent imaging of the channel using near-field excitation-scanning microscopy reveals dominant recombination and charge-separation zones. These lateral devices exhibit photodetector characteristics with a responsivity of about 51 mA/W in self-powered mode and 5.2 A/W at 5 V bias, in short-channel devices (4 {\mu}m). The low device capacitance enables a fast light-switching response of ~12 ns.