Optical properties of conjugated polymer superlattices prepared by potential-programmed electropolymerization

Abstract

Photoluminescence (PL) spectra of thin films of pyrrole and bithiophene copolymer with an alternating layered structure prepared by the potential-programmed electropolymerization method were investigated. Band edges of thin films of the copolymers were estimated by optical and electrochemical method, and they were adopted to design a superlattice potential profile of the alternating layered film. PL spectra of the copolymer films shifted to higher energies as thiophene fraction in the film decreased. This shift corresponded to band structure change. PL spectra of the layered films, designed to be type II superlattices structure, shifted to higher energies as periodicity of the layered structure became shorter. This phenomenon is to be interpreted as a quantum size effect. The observed shift was explained by the Kronig–Penney model with 0.6me (electron mass) of effective mass.