We show that this sequential two-photon photocurrent at room temperature is non-thermionic and that with light bias, the solar cells exhibit a 44% increase in photocurrent at room temperature, and a 19% increase in subgap photocurrent at 78 K.
Solar parameters of representative photovoltaic cells with or without F-process The enhanced photocurrent of the PSCs after the F-process was also verified by measuring the external quantum efficiency (EQE) of the PSCs with and without the F-process (Figure 4d). The EQE of the F-PSC increased over a broad range of visible light.
The photocurrent is calculated for the AM1.5D spectrum, which is representative of concentrated sunlight. A solar cell driven by thermionic escape would show an increasing subgap photocurrent with temperature. In contrast, we see the sub-bandgap photocurrent decrease with temperature at temperatures above 200 K.
Considering that indoor light photovoltaic cells and photodetectors operate under vastly different light intensity regimes compared with outdoor solar cells, a comprehensive understanding of the intensity dependence of charge collection (over a very broad range of intensities) is needed to chart the full potential of OPV-based technologies.
In the case of solar cells, attaining high efficiency at a reasonable cost is crucial for a viable platform. With traditional silicon-based solar cells achieving efficiencies of just over 26% 9, they are approaching their fundamental limiting efficiency of around 32%.
At very high light intensities, thermal effects may also start to play a role. These effects are generally associated with a turnover of the V OC with increasing intensity 56 but could also influence the photocurrent.