An international research group announced April 17, 2018, that it has developed an "ultra-thin organic solar cell" featuring both a high heat resistance and high energy conversion efficiency.
The group consists of researchers from Riken, Toray Industries Inc, the University of Tokyo, the Santa Barbara campus of the University of California, Waseda University, etc. The cell can be directly attached to clothes by using a "hot melt method," which is a bonding process using an adhesive that is melted by heat.
The thickness of the newly-developed ultra-thin organic solar cell (including everything from a substrate to sealing film) is only 3μm. But its maximum energy conversion efficiency reaches 10%, and its element deterioration is small enough to be ignored even at a temperature of 100°C (high thermal resistance). Also, after being stored for 80 days in the atmosphere, its performance deteriorates by less than 20%.
This time, the research group developed "PBDTTT-OFT," a new semiconductor polymer featuring both a high energy conversion efficiency and high thermal resistance. Its structure is similar to that of "PBDTTT-EFT (or PTB7-Th)," which has been widely used as a material for organic solar cells, except that it has a linear side chain. The group found that the chain enables to form a film with a high crystallinity and that the deterioration of conductivity caused by heat is smaller than in the case of conventional materials.