Efficiency Limits Of Electronically Coupled Upconverter And Quantum Ratchet Solar Cells Using Detailed Balance

The intermediate band solar cell (IBSC) and the 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 bandgap. High efficiency IBSC and QRSC devices have not yet been achieved, however, since introducing midgap 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 design was proposed in order to be less sensitive to nonradiative processes, which makes it a more practical implementation for intermediate band (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.