Polymer light-emitting electrochemical cells: Doping, luminescence, and mobility

We utilize the planar surface cell device configuration with Au contacts and a mixture of a soluble phenyl-substituted poly(para-phenylene vinylene) copolymer (superyellow), a dicyclohexano-18-crown-6 crown ether, and a LiCF3SO3 salt as the active material. Because the lowest thermal transition occurs well above room temperature (RT), we can study the charging process at an elevated temperature and probe the exact location of the electroluminescence (EL) and doping-induced quenching of photoluminescence in charged devices at RT. We also employ the same active material in thin-film field-effect transistor structures to study the influence of electrochemical doping on transistor performance. Our results demonstrate that reversible bipolar electrochemical doping indeed takes place at applied voltages above the band gap of the semiconducting polymer (Vgreater than or equal toE(g)/e), but also that limited unipolar electrochemical doping can take place at V