Lin Wang
All above effects generate direct current, the first demonstration of the alternating current photovoltaic effect (AC PV) was done by Dr. Haiyang Zou and Prof. Zhong Lin Wang at the Georgia Institute of Technology in 2017. The AC PV effect is the generation of alternating current (AC) in the nonequilibrium states when the light periodically shines at the junction or interface of material. The AC PV effect is based on the capacitive model that the current strongly depends on the frequency of the chopper. The AC PV effect is suggested to be a result of the relative shift and realignment between the quasi-Fermi levels of the semiconductors adjacent to the junction/interface under the nonequilibrium conditions. The electron flow in the external circuit back and forth to balance the potential difference between two electrodes. The organic solar cell, which the materials have no initial carrier concentration, does not have the AC PV effect.