Narrow-bandwidth solar upconversion: design principles, efficiency limits, and case studies

TL;DR

This paper models the efficiency limits of narrow-bandwidth solar upconverters integrated with single-junction solar cells, showing potential for significant efficiency improvements through bandwidth and quantum yield optimization.

Contribution

It introduces a detailed balance model for realistic narrow-band upconverters, quantifies efficiency gains, and guides future design optimization of solar upconversion systems.

Findings

Efficiency increases from 30.58% to over 43% with bandwidth expansion.

Current materials yield less than 1% efficiency improvement.

Quantum yield enhancements can boost efficiency by several percent.

Abstract

We employ a detailed balance approach to model a single-junction solar cell with a realistic narrow-band, non-unity-quantum-yield upconverter. As upconverter bandwidths are increased from 0 to 0.5 eV, maximum cell efficiencies increase from the Shockley-Queisser limit of 30.58% to over 43%. Such efficiency enhancements are calculated for upconverters with near-infrared spectral absorption bands, readily accessible with existing upconverters. While our model shows that current bimolecular and lanthanide-based upconverting materials will improve cell efficiencies by <1%, cell efficiencies can increase by several absolute percent with increased upconverter quantum yield - even without an increased absorption bandwidth. By examining the efficiency limits of a highly realistic solar cell-upconverter system, our model provides a platform for optimizing future solar upconverter designs.