Towards improved cover glasses for photovoltaic devices

Benjamin L Allsopp,Christina Stålhandske,Simon R Johnson,Robin Orman,Jonathan Booth,Gavin Sanderson,Stefan Karlsson,Ian Baistow,Anne Andersson,Lina Grund,Paul A Bingham,Peter Sundberg

doi:10.1002/pip.3334

Abstract

AbstractFor the solar energy industry to increase its competitiveness, there is a global drive to lower the cost of solar‐generated electricity. Photovoltaic (PV) module assembly is material‐demanding, and the cover glass constitutes a significant proportion of the cost. Currently, 3‐mm‐thick glass is the predominant cover material for PV modules, accounting for 10%–25% of the total cost. Here, we review the state‐of‐the‐art of cover glasses for PV modules and present our recent results for improvement of the glass. These improvements were demonstrated in terms of mechanical, chemical and optical properties by optimizing the glass composition, including addition of novel dopants, to produce cover glasses that can provide (i) enhanced UV protection of polymeric PV module components, potentially increasing module service lifetimes; (ii) re‐emission of a proportion of the absorbed UV photon energy as visible photons capable of being absorbed by the solar cells, thereby increasing PV module efficiencies and (iii) successful laboratory‐scale demonstration of proof of concept, with increases of 1%–6% in Isc and 1%–8% in Ipm. Improvements in both chemical and crack resistance of the cover glass were also achieved through modest chemical reformulation, highlighting what may be achievable within existing manufacturing technology constraints.

Highlights

Solar energy is often seen as the ultimate renewable energy because of the abundance of solar irradiation available for solar energy generation
Control of the UV absorption edge to even more effectively match the C-ethylene vinyl acetate (EVA) absorption ‘edge’ would require considerably higher doping concentrations than those that we have studied here and may produce undesirable visible absorption bands centred at 20 000 cm−1 (500 nm) and 14 300 cm−1 (700 nm), as shown for other glasses doped with 1.0-mol% Bi2O3.120 T-EVA represents a number of apparent improvements over cutting EVA (C-EVA) in terms of its UV transparency
Thermal strengthening is the predominant technique for providing protection to hailstorms for PV modules; this process can be effectively improved in terms of crack resistance (CR) by combining with CVD in a one-step process providing a thin film of Al2O3

Summary

| INTRODUCTION

Solar energy is often seen as the ultimate renewable energy because of the abundance of solar irradiation available for solar energy generation. This process is frequently called down-conversion or down-shifting, depending on the type of electronic transition involved (see Figure 2).[36,37] This aspect of photoluminescence has been considered since the 1970s38–41 and is still receiving attention.[37,42,43] By using down-conversion[44,45] or down-shifting, the solution is two-fold as the doped glass both absorbs harmful UV photons and re-emits some of this absorbed energy as photons of visible light that can be captured and converted by the solar cell It can increase the PV module service lifetime while enhancing the module efficiency. SLS glasses are optimized to a large extent based on the cost, melting and viscosity behaviour,

| EXPERIMENTAL PROCEDURES

Findings

| CONCLUSIONS