A new concept of correlated electron solar cell demonstrated ー Competing electronic phases at the interface explore higher efficiency solar cells ー



Z. G. Sheng, M. Nakamura, W. Koshibae, T. Makino, Y. Tokura, and M. Kawasaki



When a light is illuminated on a charge-ordered insulating state typically observed in transition-metal oxides, it is known that the collective activation of localized charges occurs leading to the phase transition from the insulating into metallic states. During this photoinduced phase transition, multiple charge carriers are generated from one photon. Once this multiple carrier generation is applied to a solar cell, great improvement in the photo-electron can be expected. Such a solar cell is called correlated electron solar cell and has been attracting attention as a next-generation solar cell.

The research group has investigated the photovoltaic properties under magnetic fields in heterojunctions consist of a semiconductor and perovskite-type manganites which are well-known system showing photoinduced phase transition. They found that the photo-electron conversion efficiency enhances by applying magnetic fields when the manganite has appropriate lattice distortion and chemical composition. This result indicates that the phase competing state is induced at the interface of this junction. In addition, such a junction showing clear magneto-photovoltaic effect had a larger short-circuit current compared to other junction with small magneto-photovoltaic effect. A possible scenario for this enhancement of photocurrent is that local photoinduced phase transitions occur near the interface accompanied by the multiple carrier generation. These are important results leading to the development of the correlated electron solar cell.