a compositional range of high strain point and / or intermediate expansion coefficient alkali metal free aluminosilicate and boroaluminosilicate glasses are described herein . the glasses can be used as substrates or superstrates for photovoltaic devices , for example , thin film photovoltaic devices such as cdte or cigs photovoltaic devices or crystalline silicon wafer devices . these glasses can be characterized as having strain points ≧ 600 ° c ., thermal expansion coefficient of from 35 to 50 × 10 − 7 /° c .