Role of photon recycling in perovskite solar cells

TL;DR

This paper compares photon recycling mechanisms in perovskite and GaAs solar cells, highlighting material and design limitations in perovskites that affect their potential efficiency gains from photon recycling.

Contribution

It provides a detailed analysis of how material properties and device design influence photon recycling in perovskite versus GaAs solar cells, guiding optimization strategies.

Findings

Photon recycling in perovskites is limited by non-radiative recombination at transport layers.

High mirror reflectivity (>96%) is essential for effective photon recycling in perovskites.

GaAs cells can utilize thicker layers and have less restrictive mirror requirements.

Abstract

Nearly perfect photon recycling helped GaAs cells achieve the highest efficiency ever reported for a solar cell. Recent reports of photon recycling in perovskite solar cells suggest that, once optimized, it may as well achieve GaAs-like performance. In this paper, we show that GaAs and perovskite cells recycle photons in different ways. First, although bare-perovskite has been shown to have lifetimes (~1us) in the radiative limit, non-radiative recombination at the transport layers restricts the solar cell operation far below the "photon-recycling" regime. GaAs cells have no such limitation. Second, even if the transport layers were optically and electrically perfect, the poor mobility of the perovskite layer would still restrict the optimum thickness ~1um. Thus, a very high quality mirror (reflectivity >96%) is required to utilize photon-recycling. The mirror reflectivity restriction was far more relaxed for the thicker (~2-3um) GaAs cells. Therefore, a nontrivial co-optimization of device geometry, mirror reflectivity, and material choice is necessary for achieving highest theoretical efficiency anticipated for perovskite cells.