Direct observation of energy band development in a one-dimensional biradical molecular chain by ultraviolet photoemission spectroscopy

We directly observed development of an energy band in a one-dimensional biradical molecular chain, which is constructed by exploiting the covalency between organic biradical molecules of a diphenyl derivative of s-indacenodiphenalene (Ph2-IDPL). The morphology and crystallinity of the Ph2-IDPL films were controlled by varying film growth conditions. Ultraviolet photoemission spectroscopy revealed the process of energy band development in the biradical molecular chain, clearly showing that the dispersion width of the π-band was extremely broad, exceeding 1 eV.