Micrometer-resolution fluorescence and lifetime mappings of CsPbBr$_3$ nanocrystal films coupled with a TiO$_2$ grating

TL;DR

This study demonstrates how a TiO₂ grating can significantly enhance light extraction and control emission directionality in CsPbBr₃ nanocrystal films, with detailed spatial and spectral mapping revealing underlying interactions.

Contribution

It introduces a novel approach using a TiO₂ grating to improve light emission and directionality in perovskite nanocrystal films, with detailed spatial and spectral analysis.

Findings

Tenfold increase in emission intensity via grating coupling

Decreased PL lifetime from 8.2 ns to 6.1 ns on the grating

Transformation of emission into polarized, directed light

Abstract

Enhancing light emission from perovskite nanocrystal (NC) films is essential in light-emitting devices, as their conventional stacks often restrict the escape of emitted light. This work addresses this challenge by employing a TiO$_2$ grating to enhance light extraction and shape the emission of CsPbBr$_3$ nanocrystal films. Angle-resolved photoluminescence (PL) demonstrated a tenfold increase in emission intensity by coupling the Bloch resonances of the grating with the spontaneous emission of the perovskite NCs. Fluorescence lifetime imaging microscopy (FLIM) provided micrometer-resolution mapping of both PL intensity and lifetime across a large area, revealing a decrease in PL lifetime from 8.2 ns for NC films on glass to 6.1 ns on the TiO$_2$ grating. Back focal plane (BFP) spectroscopy confirmed how the Bloch resonances transformed the unpolarized, spatially incoherent emission of NCs into polarized and directed light. These findings provide further insights into the interactions between dielectric nanostructures and perovskite NC films, offering possible pathways for designing better performing perovskite optoelectronic devices.