Fundamentals of PV Efficiency Interpreted by a Two-Level Model

TL;DR

This paper uses a simple two-level atomic model to explain photovoltaic efficiency limits, loss mechanisms, and the impact of various techniques, providing clear insights into PV operation and performance bounds.

Contribution

It introduces a two-level model that captures the core physics of PV efficiency, offering a unified reinterpretation of loss mechanisms and enhancement techniques.

Findings

The model explains conditions for reaching Carnot efficiency.

Loss mechanisms like thermalization and angle entropy are identified.

The model reproduces key PV performance insights with simplicity.

Abstract

Elementary physics of photovoltaic energy conversion in a two-level atomic PV is considered. We explain the conditions for which the Carnot efficiency is reached and how it can be exceeded! The loss mechanisms - thermalization, angle entropy, and below-bandgap transmission - explain the gap between Carnot efficiency and the Shockley-Queisser limit. Wide varieties of techniques developed to reduce these losses (e.g., solar concentrators, solar-thermal, tandem cells, etc.) are reinterpreted by using a two level model. Remarkably, the simple model appears to capture the essence of PV operation and reproduce the key results and important insights that are known to the experts through complex derivations.