1839: French physicist Antoine-Cesar Becquerel observed that shining light on an electrode submerged in electrolyte would create an electric current.
1941: American Russell Ohl invented a PN junction of silicon solar cell.
The dye sensitized solar cell was developed in 1992 by Graetzel (EPFL, Laussane, Switzerland) and utilizes nanocrystalline TiO2 as the photo absorber.