# In-situ formation of oriented perovskite nanosheets with tailored optical dipoles enabling >30% EQE in pure-red LEDs

## TL;DR

Researchers created oriented perovskite nanosheets that improve light emission efficiency in red LEDs, achieving over 30% efficiency.

## Contribution

A novel in-situ method for forming oriented perovskite nanosheets with tailored optical dipoles is introduced.

## Key findings

- The method achieves an external quantum efficiency of 31.2% in pure-red LEDs.
- The nanosheets show photoluminescence quantum yields exceeding 90%.
- Improved carrier mobility and operational stability are observed in the LEDs.

## Abstract

The integration of crystallographic control into solution-processed perovskite films remains a challenge for efficient light emission, as disordered optical dipoles fundamentally limit photon extraction, a bottleneck constraining both classical and quantum planar optoelectronic devices. Here, we address this by developing an in situ formation strategy for oriented quasi-2D perovskite nanosheets within films via ligand-engineered crystallization. By designing and orchestrating steric hindrance and π–π interactions of ligands, we direct the crystallization kinetics to yield regular face-on nanosheets exhibiting enhanced horizontal transition dipole moment orientation compared to conventional isotropic films. The in situ architectural control also elevates both the photoluminescence quantum yield beyond 90% and carrier mobility comparable to 3D perovskite levels. These synergies enable perovskite light-emitting diodes (PeLEDs) with an external quantum efficiency (EQE) of 31.2% for pure-red emission at 635 nm, comparing favorably to other pure-red PeLEDs. Concurrently, the peak luminance and operational stability of the in situ nanosheet PeLEDs exhibit significant improvements.

In situ quasi-2D perovskite nanosheet films and high-performance LEDs.