# Exceeding the Shockley-Queisser limit within the detailed balance framework

## TL;DR

This paper demonstrates that within the detailed balance framework, solar cell efficiency can surpass the Shockley-Queisser limit by considering finite absorber thickness and non-ideal absorptivity, especially for small band gap materials.

## Contribution

It shows that finite absorber thickness and realistic absorption properties can lead to efficiencies exceeding the Shockley-Queisser limit without additional mechanisms.

## Key findings

- Efficiency exceeds the Shockley-Queisser limit with finite absorber thickness.
- Non-ideal absorptivity impacts maximum achievable efficiency.
- Small band gap materials are more likely to surpass the limit.

## Abstract

The Shockley-Queisser limit is one of the most fundamental results in the field of photovoltaics. Based on the principle of detailed balance, it defines an upper limit for a single junction solar cell that uses an absorber material with a specific band gap. Although methods exist that allow a solar cell to exceed the Shockley-Queisser limit, here we show that it is possible to exceed the Shockley-Queisser limit without considering any of these additions. Merely by introducing an absorptivity that does not assume that every photon with an energy above the band gap is absorbed, efficiencies above the Shockley-Queisser limit are obtained. This is related to the fact that assuming optimal absorption properties also maximizes the recombination current within the detailed balance approach. We conclude that considering a finite thickness for the absorber layer allows the efficiency to exceed the Shockley-Queisser limit, and that this is more likely to occur for materials with small band gaps.