Transient and d.c. analysis of the operation mechanism of light-emitting electrochemical cells

¹ Departamento de Física e Ciência dos Materiais, IFSC, Universidade de São Paulo - São Carlos, SP, 13560-970, Brazil
² Universidade Estadual Paulista - UNESP, Departamento de Física - Campus de São José do Rio Preto, São José do Rio Preto, SP, 15054-000, Brazil

^(a) Present address: Universidade Estadual Paulista - UNESP - Rua Cristóvão Colombo, 2265, 15054-000, São José do Rio Preto, SP, Brazil; lucas@sjrp.unesp.br

Received: 14 August 2012
Accepted: 5 September 2012

Abstract

Light-emitting electrochemical cells (LECs) made of electroluminescent polymers were studied by d.c. and transient current-voltage and luminance-voltage measurements to elucidate the operation mechanisms of this kind of device. The time and external voltage necessary to form electrical double layers (EDLs) at the electrode interfaces could be determined from the results. In the low- and intermediate-voltage ranges (below 1.1 V), the ionic transport and the electronic diffusion dominate the current, being the device operation better described by an electrodynamic model. For higher voltages, electrochemical doping occurs, giving rise to the formation of a p-i-n junction, according to an electrochemical doping model.