Electron spin resonance study of Li-doped polyacenic semiconductor materials

Abstract

Summary form only given. ESR analyses of Li-doped polyacenic semiconductor (PAS) materials have been carried out. The pristine PAS material with the [HI]/[C] ratio of 0.22 and the electrical conductivity of 2.7x10 /sup -3/ S/cm was prepared by the pyrolysis of phenol-formaldehyde resin under non-oxidative atmosphere at 650/spl deg/C[1]. The Li doping was performed by electrochemical method using a solution of 1M LiPF/sub6/ in propylene-carbonate-diethylcarbonate as the electrolyte after Ref. 2. The doping amount was controlled by the coulometry. The maximum dopant amount of Li was achieved as much as the [C]/[Li] ratio of 2 [2]. The observed ESR spectra of the Li-doped PAS samples showed the following features: (I)The pristine and the Li-doped PAS samples showed almost the same g-values (g=2.0021-26 in the temperature range 123-293 K) (2)The Li-doping causes the increase in the peak-to-peak linewidth (/spl utri/H/subp.p./) almost proportional to the dopant amount, which is also true for the partially undoped samples. (3) In the Li-doped PAS the values of /spl utri/H/sub p.p./ decrease at low temperature (e.g., 123 K).