# Triplet-sensitization by lead halide perovskite thin films for near-infrared-to-visible upconversion

## TL;DR

This paper demonstrates that lead halide perovskite thin films can effectively sensitize rubrene for near-infrared-to-visible upconversion, achieving over 3% efficiency under 785 nm light, leveraging their optoelectronic properties.

## Contribution

It introduces the use of bulk perovskite thin films as triplet sensitizers in upconversion devices, eliminating the need for tunneling barriers used with colloidal sensitizers.

## Key findings

- Achieved over 3% upconversion efficiency under 785 nm illumination.
- Utilized perovskite thin films' long carrier lifetimes and high absorption.
- Simplified device architecture by removing tunneling barriers.

## Abstract

Lead halide-based perovskite thin films have attracted great attention due to the explosive increase in perovskite solar cell efficiencies. The same optoelectronic properties that make perovskites ideal absorber materials in solar cells are also beneficial in other light-harvesting applications and make them prime candidates as triplet sensitizers in upconversion via triplet-triplet annihilation in rubrene. In this contribution, we take advantage of long carrier lifetimes and carrier diffusion lengths in perovskite thin films, their high absorption cross sections throughout the visible spectrum, as well as the strong spin-orbit coupling owing to the abundance of heavy atoms to sensitize the upconverter rubrene. Employing bulk perovskite thin films as the absorber layer and spin-mixer in inorganic/organic heterojunction upconversion devices allows us to forego the additional tunneling barrier owing from the passivating ligands required for colloidal sensitizers. Our bilayer device exhibits an upconversion efficiency in excess of 3% under 785 nm illumination.

---
Source: https://tomesphere.com/paper/1902.05973