Assessment of the design efficacy of Eu2+ ion embedded thick scattering layers for operational photovoltaics

Abstract

A state-of-the-art encapsulation technique for evaluating a photovoltaic device in laboratory is needed for replicating real-time devices. In this context, earlier we proposed the pouch lamination as a cost-effective and reproducible lab-scale encapsulation technique. In this work, we apply this technique in evaluating the optical and electrical performances of a mc-Si device with a front spectral shifting layer before and after encpasulation. Our coating contains the red-emitting nitride phosphor CaAlSiN3:Eu2+ (CASN:Eu2+) in (poly)-methyl methacrylate (PMMA). On coating, a drastic reduction in the device's reflectance was observed below 450 nm. Correspondingly, the external and internal quantum efficiencies of the devices are also improved relative to the bare. When irradiated by an AM1.5G source, the electrical parameters remain of the device remain unaffectd after the coating. However, on encapsulating the coated device, impedance losses drastically reduce its conversion efficiency. This paper thus reveals the need for including an encapsulant while demonstrating device modifications through optical coatings.

Keywords

• Luminescence
• Downshifting
• Phosphor
• Encapsulant
• Scattering