%0 Journal Article
%T Photovoltaic properties and annealing effects of a low bandgap copolymer containing dithienothiophene and benzothiadiazole units
%A T. L. Wang
%A Y. T. Shieh
%A C. H. Yang
%A T. H. Ho
%J eXPRESS Polymer Letters
%D 2013
%I Budapest University of Technology
%R 10.3144/expresspolymlett.2013.6
%X A conjugated alternating copolymer as the donor material of the active layer in polymer solar cells has been designed and synthesized via Stille coupling reaction. The alternating structure consisted of 3,5-didecanyldithieno[3,2-b:2',3'-d]thiophene (DDTT) donor unit and 5,6-bis(tetradecyloxy)benzo-2,1,3-thiadiazole (BT) acceptor unit. Since both units have been attached pendant chains, the polymer was soluble in common organic solvents. UV-vis spectrum exhibited a broad absorption band in the range of 270¨C780 nm and a low bandgap of 1.83 eV. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the polymer were estimated to be ¨C5.10 and ¨C3.27 eV, respectively. Based on the ITO/PEDOT:PSS/PDDTTBT:PCBM/Al device structure, the power conversion efficiency (PCE) under the illumination of AM 1.5 (100 mW/cm2) was 0.127%. The effects of annealing temperature (50¨C150¡ãC) for 30 min on the device performance were studied. It was found that PCE of 0.292% could be acquired under the annealing condition at 50¡ãC for 30 min. The improved device efficiency under the optimal condition was confirmed by the higher light harvest in UV-vis spectra, the enhanced quenching of photoluminescence (PL) emission, and the improved nanoscale morphology by atomic force microscopy (AFM) examination.
%K Nanomaterials
%K polymer solar cells
%K low bandgap
%K annealing
%U http://www.expresspolymlett.com/letolt.php?file=EPL-0003799&mi=cd