Description
Solar cells deployed for space, terrestrial, and commercial applications must achieve long-term stability and efficient harvesting of the solar spectrum. Ultraviolet (UV) light is a major stressor of solar cell stability and power conversion efficiencies (PCEs) during extended operation, particularly in the case of perovskite solar cells. UV irradiation of solar cells breaks organic bonds, introduces oxygen defects, and increases rates of electron trapping, degrading photocurrent. In other solar cell technologies such as silicon, UV photons can increase recombination defects in specific cell layers, largely reducing electrical performance. UV exposure can also darken the cover glasses of cells and induce colour centers, diminishing light transmission to absorber layers and thus causing a significant loss of PCE.
The application of UV downshifting can mitigate the effects of UV irradiation on solar cells, while potentially increasing photocurrent generated by current technologies. Through the absorption of high-energy photons and re-emission of lower-energy (longer-wavelength) photons, known as Stokes shifting, this strategy can improve UV stability and PCE simultaneously. In this work, six different UV-downshifting cover glasses are physically characterised as potential cell superstrates and tested with perovskite solar cells, with peak emission wavelengths ranging from blue (400 nm) to red (750 nm). Preliminary results show that the external quantum efficiency (EQE) of cells with the UV-downshifting glasses laid on top of an encapsulated cell exceeds the performance of a standard quartz glass control and exceeds the expected performance after Fresnel reflection at normal incidence. Small increases in EQE are found for one sample using this testing method, while three other samples show values close to those of a base cell with no additional glass layer on top.
| I am the presenting author | Yes |
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