NOVELTY - A glass substrate (1) has composition containing (in %mass) silica (58.5-69.5), alumina (2.5-9.9), lithium oxide (0-2.5), sodium oxide (0-6), potassium oxide (0-6), magnesium oxide (0-5.2), calcium oxide (3-13), strontium oxide (10-27), barium oxide (0-5), titanium oxide (0-3), zirconium oxide (0-9.8), and does not contain boron trioxide. The glass substrate has glass transition temperature of more than 555 degrees C, liquidus temperature of 1200 degrees C or less and average coefficient of thermal expansion of 75x 10-7/ degrees C or less at 50-350 degrees C.    USE - Glass substrate for compound semiconductor solar cell. Uses include but are not limited to amorphous solar battery, cover glass for crystalline silicon solar cell, tandem type solar cell, field emission display and plasma display panel.    ADVANTAGE - The glass substrate has favorable thermal expansion coefficient, high strain point and is manufactured continuously. Since the glass substrate contains reduced amount of barium oxide, the substrate having low density is provided. Since the substrate does not contain boron trioxide, the load on the brick of the smelter during the manufacture of the substrate is reduced. The solar cell having high photoelectric conversion efficiency is manufactured.    DETAILED DESCRIPTION - A glass substrate has composition containing (in %mass) silica (58.5-69.5), alumina (2.5-9.9), lithium oxide (0-2.5), sodium oxide (0-6), potassium oxide (0-6), magnesium oxide (0-5.2), calcium oxide (3-13), strontium oxide (10-27), barium oxide (0-5), titanium oxide (0-3), zirconium oxide (0-9.8), and does not contain boron trioxide. The sum total content of silica and alumina is 73 %mass or less, and sum total content of lithium oxide, sodium oxide and potassium oxide is less than 6 %mass. The sum total content of magnesia and calcium oxide is 3-16 %mass. The sum total content of strontium oxide and barium oxide is 10-27 %mass, the sum total content of magnesium oxide, calcium oxide, strontium oxide and barium oxide is 21-33 %mass and the molar fraction of magnesium oxide and calcium oxide is 0.2-1.0. The glass substrate has glass transition temperature of more than 555 degrees C, liquidus temperature of 1200 degrees C or less and average coefficient of thermal expansion of 75x 10-7/ degrees C or less at 50-350 degrees C. An INDEPENDENT CLAIM is included for manufacture of the glass substrate.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view of the structure of the solar cell.    Glass substrate (1)    Transparent conductive film (2)    Cadmium sulfide thin film (3)    Cadmium telluride thin film (4)    Metal electroconductive film (5)