Photodiode Response in a CH$_3$NH$_3$PbI$_3$/CH$_3$NH$_3$SnI$_3$ Heterojunction

TL;DR

This study reveals that a heterojunction diode made of CH$_3$NH$_3$PbI$_3$ and CH$_3$NH$_3$SnI$_3$ exhibits reversible polarity under illumination, demonstrating a novel photo-tunability feature with potential for new opto-electronic applications.

Contribution

It reports the first observation of complete diode polarity reversal in a perovskite heterojunction under light exposure, highlighting a new photo-tunability mechanism.

Findings

Diode exhibits polarity reversal upon red laser illumination.

Heterojunction is highly sensitive to light intensity.

First demonstration of reversible diode polarity in this material system.

Abstract

Since the discovery of its photovoltaic properties organometallic salt CH$_3$NH$_3$PbI$_3$ became the subject of vivid interest. The material exhibits high light conversion efficiency, it lases in red color, and it can serve as the basis for light emitting diodes and photodetectors. Here we report another surprising feature of this material family, the photo-tunability of the diode response of a heterojunction made of CH$_3$NH$_3$PbI$_3$ and its close relative, CH$_3$NH$_3$SnI$_3$. In the dark state the device behaves as a diode, with the Sn homologue acting as the "p" side. The junction is extremely sensitive to illumination. A complete reversal of the diode polarity, the first observation of its kind, is seen when the junction is exposed to red laser light of 25 mW/cm$^2$ or larger power density. This finding opens up the possibility for a novel class of opto-electronic devices.