Glass substrate for Cu-In-Ga-Se solar cell and solar cell using same

A glass substrate, comprising:

• a substrate having a surface and comprising a glass material,
• wherein the glass material has a glass transition temperature of at least 580° C. and an average thermal expansion coefficient of from 70×10−7 to 100×10−7/° C.,
• the substrate comprises at least one of CaO, SrO and BaO such that a ratio of an average total amount in atom % of Ca, Sr and Ba within from 10 to 40 nm in depth from the surface of the substrate to a total amount in atom % of Ca, Sr and Ba at 5,000 nm in depth from the surface of the substrate is at most 0.35,
• the substrate comprises Na2O such that a ratio of an average Na amount in atom % within from 10 to 40 nm in depth from the surface of the substrate after a heat treatment at 600° C. under a N2 atmosphere for 1 hour to an average Na amount before the heat treatment is at least 1.5, and
• the substrate comprises, at 5,000 nm or more in depth from the surface of the substrate, as represented by mass % based on oxides, from 53 to 72% of SiO2, from 1 to 15% of Al2O3, from 0.5 to 9% of MgO, from 0.1 to 11% of CaO, from 0 to 11% or SrO, from 0 to 11% or BaO, from 2 to 11% of Na2O, from 2 to 21% of K2O and from 0 to 10.5% of ZrO2, provided that MgO+CaO+SrO+BaO is from 4 to 25%, CaO+SrO+BaO is from 2 to 23%, Na2O+K2O is from 8 to 22%, and Na2O/(CaO+SrO+BaO)≦1.2.