Lanthanide-based downshifting layers tested in a solar car race

Sandra F H Correia,Ana R N Bastos,Luís D Carlos,Lianshe Fu,Rute A S Ferreira,Paulo S André

doi:10.29026/oea.2019.190006

Abstract

The mismatch between the AM1.5G spectrum and the photovoltaic (PV) cells absorption is one of the most limiting factors for PV performance. To overcome this constraint through the enhancement of solar energy harvesting, luminescent downshifting (LDS) layers are very promising to shape the incident sunlight and, thus, we report here the use of Tb3+- and Eu3+-doped organic-inorganic hybrid materials as LDS layers on Si PV cells. Electrical measurements on the PV cell, done before and after the deposition of the LDS layers, confirm the positive effect of the coatings on the cell’s performance in the UV spectral region. The maximum delivered power and the maximum absolute external quantum efficiency increased 14% and 27%, respectively. Moreover, a solar powered car race was organized in which the small vehicle containing the coated PV cells presented a relative increase of 9% in the velocity, when compared to that with the uncoated one.

Highlights

The mismatch between the AM1.5G spectrum and the photovoltaic (PV) cells absorption is one of the most important factors contributing to limit the maximum efficiency of the cells, accounting for the losses associated with the excess energy of the absorbed above-bandgap energy photons and with the non-absorption of photons with energy below the bandgap of the PV cell
We report Eu3+- and Tb3+-doped organic-inorganic hybrids (e.g., the d-U(600) di-ureasil and the t-U(5000) tri-ureasil) to be used as luminescent downshifting (LDS) coatings on Si-based PV cells
Luminescent downshifting (LDS) coatings based on Eu3+ and Tb3+-doped organic-inorganic hybrid materials are reported

Summary

Introduction

The mismatch between the AM1.5G spectrum and the photovoltaic (PV) cells absorption is one of the most important factors contributing to limit the maximum efficiency of the cells, accounting for the losses associated with the excess energy of the absorbed above-bandgap energy photons and with the non-absorption of photons with energy below the bandgap of the PV cell. One way to overcome these losses is by shaping the incident sunlight through the use of luminescent downshifting (LDS) layers[4,5], a relatively direct and cost-effective method to improve conversion efficiency of PV cells These converting layers are coatings directly applied on the PV cell surface that are able to absorb the incident radiation unused by the PV cell which is re-emitted at a usable wavelength (or refracted towards the PV cell)[6,7]. These LDS layers reveal analogous optical efficiency under diffuse or direct radiation, providing analogous output under cloudy days, which does not happen for bare PV cells. These LDS layers may act as an antireflective coating and increase the amount of absorbed photons[8]

Methods

Results

Conclusion