Perovskite/silicon tandem solar cells: Effect of luminescent coupling and bifaciality

TL;DR

This study models the energy output of perovskite/silicon tandem solar cells, highlighting how luminescent coupling and bifacial operation can significantly improve efficiency and influence optimal material choices.

Contribution

It is the first to quantify luminescent coupling effects in tandem cells and demonstrates how this relaxes bandgap constraints, guiding better material optimization.

Findings

Luminescent coupling can utilize over 50% of excess electron-hole pairs.

Luminescent coupling relaxes the top-cell bandgap constraints.

Bifacial operation shifts the optimal perovskite bandgap to 1.60-1.65 eV.

Abstract

The power conversion efficiency of the market-dominating silicon photovoltaics approaches its theoretical limit. Bifacial solar operation with harvesting additional light impinging on the module back and the perovskite/silicon tandem device architecture are among the most promising approaches for further increasing the energy yield from a limited area. Here, we calculate the energy output of perovskite/silicon tandem solar cells in monofacial and bifacial operation considering, for the first time, luminescent coupling between two sub-cells. For energy yield calculations we study idealized solar cells at both, standard testing as well as realistic weather conditions in combination with a detailed illumination model for periodic solar panel arrays. Considering typical, experimental photoluminescent quantum yield values we find that more than 50% of excess electron-hole pairs in the perovskite top cell can be utilized by the silicon bottom cell by means of luminescent coupling. As a result, luminescent coupling strongly relaxes the constraints on the top-cell bandgap in monolithic tandem devices. In combination with bifacial operation, the optimum perovskite bandgap shifts from 1.71 eV to the range 1.60-1.65 eV where already high-quality perovskite materials exist. The results can hence change a paradigm in developing the optimum perovskite material for tandem solar cells.