An organic solar cell is composed of a donor molecule that emits an electron by light and is positively charged, and an acceptor molecule that receives an electron and is negatively charged.A structure in which donors and acceptors are regularly and alternately arranged, which is called an interpenetrating structure, is considered to be the ultimate ideal structure as a material for organic solar cells because it can efficiently create a long-life charge separation state.However, in general, donors and acceptors were mixed in a disorderly manner, and it was very difficult to precisely control their arrangement.

　The research group has long found that by constraining a polymer in the pore space of a porous metal complex (MOF), the orientation direction and the number of accumulations of polymer chains can be precisely controlled at the molecular level.

　Taking advantage of this finding, in this study, the donor molecule polythiophene is synthesized in a MOF containing titanium oxide known as an acceptor molecule to create a structure in which donors and acceptors are regularly and alternately arranged at the molecular level. I succeeded in creating it.As a result, the life of the electric charge, which is the carrier of the electric current, is about 1000 times longer than before, and we succeeded in dramatically stabilizing the extremely unstable electric charge.

　By applying this result, it is expected that it will lead to higher efficiency of various energy conversion devices such as organic solar cells.

Paper information:[Nature Communications] A phase transformable ultrastable titanium-carboxylate framework for photoconduction