Equivalent Circuit Description of Non-compensated n-p Codoped TiO2 as Intermediate Band Solar Cells

TL;DR

This paper models non-compensated n-p codoped TiO2 as an intermediate band solar cell using equivalent circuits, showing efficiencies surpassing the Shockley-Queisser limit and revealing double peaks in quantum efficiency.

Contribution

It introduces an equivalent circuit model for non-compensated n-p codoped TiO2 IBSCs, providing insights into efficiency limits and circuit parameters for device development.

Findings

Maximum efficiency of 57% with current extraction

Efficiency of 53% without current extraction

Identification of double peaks in quantum efficiency

Abstract

The novel concept of non-compensated n-p codoping has made it possible to create tunable intermediate bands in the intrinsic band gap of TiO2, making the codoped TiO2 a promising material for developing intermediate band solar cells (IBSCs). Here we investigate the quantum efficiency of such IBSCs within two scenarios - with and without current extracted from the extended intermediate band. Using the ideal equivalent circuit model, we find that the maximum efficiency of 57% in the first scenario and 53% in the second are both much higher than the Shockley-Queisser limit from single gap solar cells. We also obtain various key quantities of the circuits, a useful step in realistic development of TiO2 based solar cells invoking device integration. These equivalent circuit results are also compared with the efficiencies obtained directly from consideration of electron transition between the energy bands, and both approaches reveal the intriguing existence of double peaks in the maximum quantum efficiency as a function of the relative location of IBs.