A dithienyl benzotriazole-based polyfluorene: Synthesis and applications in polymer solar cells and red light-emitting diodes

摘要

A new donor-acceptor type polyfluorene derivative, poly[9,9-dioctyl-2,7- fluorene-alt-(4,7-bis(2′-thienyl)-2-octyl-2,1,3-benzotriazole)] (PFDTBTz), is synthesized by a Suzuki cross-coupling polymerization reaction. The optical, electrochemical, photovoltaic, and electroluminescence properties of PFDTBTz are investigated in detail. The maximum power conversion efficiency (PCE) of the PSCs based on PFDTBTz/PC71BM (1:2 w/w) reaches 2.1% with a short circuit current density (J_(sc)) of 5.73 mA · cm~(-2), an open circuit voltage (V_(oc)) of 0.84 V, and a fill factor (FF) of 0.44 under AM 1.5G, 100 mW · cm-2 illumination. Polymer light-emitting diodes (PLEDs) are fabricated in an ITO/PEDOT:PSS (30 nm)/PFDTBTz (60 nm)/BAlq (40 nm)/Cs2CO3:Ag configuration and light emission is observed at a voltage greater than 8.0 V. The EL device shows almost pure red and the efficiency is very stable when the current density is increased, making it useful for commercial applications. A donor-acceptor-type polyfluorene derivative, poly'9,9-dioctyl-2,7-fluorene- alt-(4,7-bis(2′- thienyl)-2-octyl-2,1,3- benzotriazole)' (PFDTBTz), is synthesized by a Suzuki polymerization reaction. BHJ solar cells based on blends of PFDTBTz with PC 71BM have a PCE of 2.1% under 100 mW · cm~(-2), AM 1.5 illumination. The EL device shows pure red emission with a maximum brightness of 3 588 cd · m~(-2) and a maximum luminance efficiency of 0.6 cd · A~(-1)