How Good Can 2D Excitonic Solar Cells Be?

TL;DR

This paper analyzes the potential of 2D excitonic solar cells, predicting a maximum efficiency of around 9.22% and highlighting their suitability for lightweight applications like aerospace and wearables.

Contribution

The study provides a comprehensive optical and electronic analysis of monolayer TMDC-based excitonic PVs and proposes optimized device structures with high specific power.

Findings

Predicted PCE of 9.22% for optimized superlattice structures.

Potential specific power exceeding 100 W g-1.

Limitations of <10% efficiency for 2D excitonic solar cells.

Abstract

Excitonic semiconductors have been a subject of research for photovoltaic applications for many decades. Among them, the organic polymers and small molecules based solar cells have now exceeded 19% power conversion efficiency (PCE). While organic photovoltaics (OPVs) are approaching maturity, the advent of strongly excitonic inorganic semiconductors such as two-dimensional transition metal dichalcogenides (TMDCs) has renewed interest in excitonic solar cells due to their high-optical constants, stable inorganic structure and sub-nm film thicknesses. While several reports have been published on TMDC based PVs, achieving power conversion efficiencies higher than 6% under one-sun AM1.5G illumination has remained challenging. Here, we perform a full optical and electronic analysis of design, structure and performance of monolayer TMDC based, single-junction excitonic PVs. Our computational model with optimized properties predicts a PCE of 9.22% in a superlattice device structure. Our analysis suggests that, while the PCE for 2D excitonic solar cells may be limited to < 10%, a specific power > 100 W g-1 may be achieved with our proposed designs, making them attractive in aerospace, distributed remote sensing, and wearable electronics.