Efficiency scaling of non-coherent upconversion

TL;DR

This paper develops a 1D model to understand how physical processes like diffusion and decay affect the efficiency of non-coherent light upconversion, providing scaling laws to optimize material design.

Contribution

It introduces a theoretical model that reveals how the ratio of molecular species and physical parameters influence upconversion efficiency, guiding experimental material optimization.

Findings

Optimal molecular ratio depends on diffusion and decay rates.

Scaling laws relate maximum efficiency to physical process rates.

Model suggests pathways to enhance upconversion in materials.

Abstract

A very promising approach to obtain efficient upconversion of light is the use of triplet-triplet annihilation of excitations in molecular systems. In real materials, besides upconversion, many other physical processes take place - fluorescence, non-radiative decay, annihilation, diffusion - and compete with upconversion. The main objective of this work is to design a proof of principle model that can be used to shed light on the relevance of the interaction between the different physical processes that take part in these kinds of systems. Ultimately, we want to establish general principles that may guide experimentalists toward the design of materials with maximum efficiency. Here we show, in a 1D model system, that even in the presence of these processes upconversion can be optimized by varying the ratio between the two molecular species present in this kind of materials. We derive scaling laws for this ratio and for the maximum efficiency of upconversion, as a function of the diffusion rate J, as well as of the creation and of the decay rate of the excitations.