Mixed Halide Perovskite Light Emitting Solar Cell

TL;DR

This study demonstrates a mixed halide perovskite device that can switch between high-efficiency solar cell and LED modes through photo-poling, revealing reversible halide segregation and improved LED stability.

Contribution

It introduces a dual functional perovskite device capable of switching between solar cell and LED modes with high efficiency via in-situ ion migration induced by light exposure.

Findings

Switchable device between solar cell and LED modes with low threshold voltage.

Photo-poling stabilizes electroluminescence and enhances LED performance.

Halide segregation improves LED brightness but temporarily reduces photovoltaic efficiency.

Abstract

Organic-inorganic halide perovskites recently have emerged as a promising material for highly effective light-emitting diodes (LEDs) and solar cells (SCs). Despite efficiencies of both perovskite SCs and LEDs are already among the best, the development of a perovskite dual functional device that is capable of working in these two regimes with high efficiencies is still challenging. Here we demonstrate that the dual functional device based on mixed halide perovskite CH3NH3PbBr2I can be switched from SC to LED with low threshold voltage Vth < 2 V by exposing to Sun at open circuit Voc or at small bias voltage of Vpol ~ 1 - 2 V. Such photo-poling creates in-situ p-i-n junction via methylammonium (CH3NH3+, MA+) and I-/Br- ions migration to interfaces, lowering charge injection barriers, and self-balancing injection currents in perovskite LED. We show that before the photo-poling, the electroluminescence (EL) is highly unstable in LED regime, whereas after the photo-poling, stabilized EL exhibits unusual dynamics, increasing with time and poling cycle number, while Vth and injection current decrease with cycling runs. Additionally, photo-induced and current-induced halide segregation accumulates with cycling, that is found beneficial for LED, increasing its efficiency and brightness, but reversibly degrading photovoltaic (PV) performance, which can be easily recovered.