Efficiency limits of electronically-coupled upconverter and quantum ratchet solar cells using detailed balance

TL;DR

This paper analyzes the efficiency limits of electronically-coupled upconverter and quantum ratchet solar cells, showing ECUC's practical advantages and potential for surpassing standard solar cell efficiencies.

Contribution

It demonstrates that ECUC can match QRSC efficiencies in detailed balance and is more resilient to nonradiative losses, offering a new approach for IB solar cell development.

Findings

ECUC achieves similar efficiencies to QRSC in theory.

ECUC is less sensitive to nonradiative recombination.

Potential materials and dopants for ECUC are identified.

Abstract

The intermediate band solar cell (IBSC) and quantum ratchet solar cell (QRSC) have the potential to surpass the efficiency of standard single-junction solar cells by allowing sub-gap photon absorption through states deep inside the band gap. High efficiency IBSC and QRSC devices have not yet been achieved, however, since introducing mid-gap states also increases recombination, which can harm the device. We consider the electronically coupled upconverter (ECUC) solar cell and show that it can achieve the same efficiencies as the QRSC. Although they are equivalent in the detailed balance limit, the ECUC is less sensitive to nonradiative processes, which makes it a more practical implementation for IB devices. We perform a case study of crystalline-silicon based ECUC cells, focusing on hydrogenated amorphous silicon as the upconverter material and highlighting potential dopants for the ECUC. These results illustrate a new path for the development of IB-based devices.