A Markov Chain Approach for Defining the Fundamental Efficiency Limits of Classical and Bifacial Multi-junction Tandem Solar Cells

TL;DR

This paper introduces a simple Markov chain method to analytically determine the fundamental efficiency limits of classical and bifacial multi-junction tandem solar cells, simplifying optimization and revealing key insights.

Contribution

It presents an innovative Markov chain approach that analytically captures the physics of tandem solar cell efficiency limits, simplifying the optimization process.

Findings

Reproduces known results of tandem cell efficiencies

Highlights asymptotic efficiency gains of bifacial designs

Provides analytical insights into tandem cell optimization

Abstract

Bifacial tandem cells promise to reduce three fundamental losses (above-bandgap, below bandgap, and the uncollected light between panels) inherent in classical single junction PV systems. The successive filtering of light through the bandgap cascade, and requirement of current continuity make optimization of tandem cells difficult, accessible only to numerical solution through computer modeling. The challenge is even more complicated for bifacial design. In this paper, we use an elegantly simple Markov chain approach to show that the essential physics of optimization is intuitively obvious, and deeply insightful results can obtained analytically with a few lines of algebra. This powerful approach reproduces, as special cases, all the known results of traditional/bifacial tandem cells, and highlights the asymptotic efficiency gain of these technologies.