For 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 I sc and 1%-8% in I pm. 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. K E Y W O R D S chemical properties, cover glass, mechanical properties, optical properties, photoluminescence, PV modules, strengthening of glass 1 | INTRODUCTION Solar energy is often seen as the ultimate renewable energy because of the abundance of solar irradiation available for solar energy generation. In only 90 min, the Earth receives enough energy from the sun to provide its entire annual energy requirements. 1 Chapin, Fuller and Pearson invented the first practical photovoltaic (PV) cell in 1954, 2 and since the year 2000, installed PV capacity has experienced an almost exponential growth. 3 The installed PV capacity can be regulated politically but that is largely achieved on a national level and may be subject to change within just a few years. The growth of the solar energy market has been driven by the reduction of costs. For solar or any other renewable energy source, it has been a necessity to compete on an economical level (i.e., reaching so-called grid parity), and
