Enhancing silicon solar cells with singlet fission: the case for Foerster resonant energy transfer using a quantum dot intermediate

TL;DR

This paper explores enhancing silicon solar cell efficiency by using singlet fission in polyacenes combined with Foerster Resonant Energy Transfer via lead sulfide quantum dots as intermediaries, potentially surpassing traditional limits.

Contribution

It introduces a modified FRET model incorporating quantum dots as intermediaries, demonstrating high transfer efficiencies at short distances for solar cell applications.

Findings

FRET efficiency >50% at ~1 nm distance

Modified FRET model accounts for quantum dot geometry

Quantum dots enable spin-forbidden energy transfer

Abstract

One way for solar cell efficiencies to overcome the Shockley-Queisser limit is downconversion of high-energy photons using singlet fission (SF) in polyacenes like tetracene (Tc). SF enables generation of multiple excitons from the high-energy photons which can be harvested in combination with Si. In this work we investigate the use of lead sulfide quantum dots (PbS QDs) with a band gap close to Si as an interlayer that allows Foerster Resonant Energy Transfer (FRET) from Tc to Si, a process that would be spin-forbidden without the intermediate QD step. We investigate how the conventional FRET model, most commonly applied to the description of molecular interactions, can be modified to describe the geometry of QDs between Tc and Si and how the distance between QD and Si, and the QD bandgap affects the FRET efficiency. By extending the acceptor dipole in the FRET model to a 2D plane, and to the bulk, we see a relaxation of the distance dependence of transfer. Our results indicate that FRET efficiencies from PbS QDs to Si well above 50 % are be possible at very short, but possibly realistic distances of around 1 nm, even for quantum dots with relatively low photoluminescence quantum yield.