Efficient Red Downshifting in Layered Structure: A Broad Spectral Converter for Enhancing Photo-response of Solar Cell

Abstract

Spectral convertors are promising materials for solar cells as they engineered the band gap necessary for suppressing the losses. Existing spectral convertors have small stokes shift which exerts re-absorption losses due to the overlap of spectrum and limits light catching ability. Here we present large stoke shift chromium doped rhombohedral Al₂O₃: Cr³⁺ as a spectral convertor from UV–VIS to red region as single doped with maximum coverage of solar spectrum in UV region. The large stoke shifts in red region around 694 nm originate from ²E_g to ⁴A_2g and broad absorption originates from \(^{{\text{4}}}{{\text{A}}_{{\text{2g}}}}{ \to ^{\text{4}}}{{\text{T}}_{{\text{1g}}}},{{\text{ }}^{\text{4}}}{{\text{A}}_{{\text{2g}}}}{ \to ^{\text{4}}}{{\text{T}}_{{\text{2g}}}}\). This broad absorption (300–600 nm) and large stokes shift emission at 694 nm suggest that the Cr³⁺ dopant rhombohedral Al₂O₃ is well suited as spectral convertors for enhancing the efficiency of the solar cell through better matching of spectral response with spectral distribution of light striking on the solar cell.