Exploratory Synthesis and Luminescence Study of the First π-Conjugated Tin-Based Alternating Copolymers for Blue Light-Emitting Diodes at the Very Low Operating Voltage

Abstract

Tin-based alternating copolymers with a uniform π-conjugated segment were synthesized using the Heck reaction between distyrylstannane monomer and various difunctionalized monomers. The UV−vis absorption maximum peaks of the resulting polymers in chloroform solution and in thin films appeared in the wavelength range of 347−394 nm. Upon photoexcitation with light of wavelength 350 nm, their photoluminescence spectra exhibited an emissive maximum peak around 470−502 nm, corresponding to blue light emission. Multilayered light-emitting diodes with ITO/PEDOT (50 nm)/polymer (80 nm)/Ca (50 nm)/Al (200 nm) composition were fabricated. These LED devices exhibited an emissive maximum peak in the range of 464−472 nm. All of the materials exhibited a very low turn-on voltage of less than 4 V. From cyclic voltammetric studies and optical data, the LUMO level is estimated to be 3.20 eV for SnPhFPV and 2.90 eV for SnPhPVK, and the ionization potentials (HOMO level) were estimated to be 5.90 eV for SnPhFPV and 5.60 eV ...