Thin Solid Films, Vol.518, No.18, 5292-5299, 2010
Investigation of photophysical, morphological and photovoltaic behavior of poly(p-phenylene vinylene) based polymer/oligomer blends
Two cyano oligo-phenylene-vinylenes [alpha-CNOPV and beta-CNOPV] distinguished by the position of cyano (CN) group at the vinylic double bond were synthesized. The acceptor oligomer CNOPVs were blended with poly (2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylenevinylene) MEH-PPV to achieve alpha and beta. The pronounced influence of cyano position on the photophysical and morphological properties of blends was observed through UV-vis absorption, photoluminescence and atomic force microscopy. The optical characterization suggests wider spectral photon harvesting in alpha blends and more planar conformation of molecules in beta blends. The steady-state and time-resolved photoluminescence study provides evidence for efficient energy transfer from alpha-CNOPV to MEH-PPV. On the other hand, the 3:1 beta blend exhibits quenching of PL intensity indicative of charge transfer. In addition, the feasibility of MEH-PPV:CNOPV blends in organic photovoltaic devices have been investigated. The initial device parameters show that power conversion efficiency is as high as 0.05% in beta 1:1 devices. The photovoltaic efficiencies were limited by weak exciton dissociation in alpha blends while poor morphology restricted the efficiency in beta blends. (C) 2010 Elsevier B.V. All rights reserved.
Keywords:MEH-PPV;CN-PPV;Polymer-oligomer blend;Energy transfer;Transient photoluminescence;Photovoltaic cells