The correlation between limiting efficiency of indoor photovoltaics and spectral characteristics of multi-color white LED sources

Abstract

The correlation between the optimal performance of indoor photovoltaics (IPVs) and spectral characteristics of white light-emitting diode (LED) sources has been investigated theoretically. We calculated the Schockley–Queisser limit of IPVs under multi-color white LEDs with different correlated color temperature (CCT), color rendering index (CRI) and luminous efficacy of radiation (LER). It is found that the optimal bandgap for an IPV cell is not only influenced by CCT, but also by LER and CRI. However, the main factor that affects the maximum power conversion efficiency (PCE) is CCT, and the maximum PCE is relatively independent of the CRI and LER under the same condition of CCT. The maximum PCE decreases with the increase of CCT. Based on the analysis of the energy loss within IPVs, it is found that the value of the optimal bandgap is sensitive to the fraction of red light in the spectrum of white LEDs. The maximum PCE is primarily limited by the relaxation to band edge loss, which is caused by the high-energy blue or cyan light in the spectrum of white LEDs.