Raman studies of polarons and bipolarons in sodium-doped poly-p-phenylene

Raman spectra have been measured of heavily Na-doped poly-p-phenylene (PPP) with various laser lines in the 488.0-1064 nm region. They have been compared with those of the radical anions and dianions of p-oligophenyls (p-terphenyl, p-quaterphenyl, p-quinquephenyl and p-sexiphenyl). The Raman spectra of Na-doped PPP excited at 488.0-514.5 nm and 632.8-1064 nm are attributed, respectively, to negative polarons and bipolarons. Electronic absorption spectra of doped PPP are explained by the coexistence of negative polarons and bipolarons on the basis of the Raman results.