Enhanced Charge Balance for Efficient Electroluminescence from Cesium Copper Halides

Area of Science:

• Materials Science
• Optoelectronics
• Solid-State Chemistry

Background:

• Cesium copper halides offer high photoluminescence quantum efficiency and stability, making them promising alternatives to lead halides in perovskite light-emitting diodes (LEDs).
• A significant challenge in cesium copper halide LEDs is achieving charge balance due to their shallow conduction band and incompatible electron transport layers, leading to hole accumulation and nonradiative recombination.

Purpose of the Study:

• To address the charge balance issue in cesium copper halide LEDs by suppressing hole injection.
• To improve the external quantum efficiency (EQE) of cesium copper halide-based light-emitting devices.

Main Methods:

• Modification of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer with polyethylenimine (PEI).
• Fabrication and characterization of cesium copper halide LEDs incorporating the modified PEDOT:PSS layer.

Main Results:

• The modification effectively suppressed hole injection at the interface between the emitting layer and the electron transport layer.
• The developed cesium copper halide LEDs achieved a high external quantum efficiency (EQE) of 5.6%.

Conclusions:

• Suppressing hole injection through PEDOT:PSS modification with PEI is an effective strategy to enhance charge balance in cesium copper halide LEDs.
• This approach represents a significant advancement in device architecture for efficient electroluminescence from cesium copper halides, paving the way for lead-free lighting solutions.