End-capped thiophene-free organic dye for dye-sensitized solar cell: Optimized donor, broadened spectra and enhanced open-circuit voltage

We report on a new series thiophene-free organic dyes featured with 2,7-disubstituted carbazole as a it-linker for dye-sensitized solar cells (DSSCs). Three different tert-butyl-capped N-arylamine has been introduced as donor group of this series of dyes (coded DH-13 to DH-15). These dyes have been systematically characterized and employed in DSSC devices, leading to the power conversion efficiencies of 5.06%, 4.38% and 1.75% for DH-13, DH-14 and DH-15, respectively. For a further modification of DH-13, 2,1,3-benzothiadiazole has been inserted to construct a D-A-Tc-A structured dye (DH-16) which achieves a power efficiency of 6.76% without coadsorbent that reached 89% of the reference dye N719-based cell. This result indicates that 2,7-disubstituted carbazole could be a promising building block to construct high-performance metal-free organic sensitizer even without most commonly used thiophene derivatives. (C) 2015 Elsevier Ltd. All rights reserved.