1839
The effect which underlies solar cells was first experimentally demonstrated by French physicist A. E. Becquerel in 1839 when he built the world's first photovoltaic cell. In 1883 the first solid state photovoltaic cell was built by the American Charles Fritts. The device was only around 1% efficient. In 1888 Russian physicist Aleksandr Stoletov built the first photoelectric cell based on the outer photoelectric effect discovered by Heinrich Hertz earlier in 1887.