First principles study of thieno[2,3-b]indole-based organic dyes for dye-sensitized solar cells: Screen novel π-linkers and explore the interface between photosensitizers and TiO2

Four organic compounds with different pi-linkers are theoretically explored as potential photosensitizers for application in dye-sensitized solar cells (DSSCs). Besides the isolated dyes, the interfacial properties of dyes adsorbed on TiO2 anatase (101) surface are theoretically investigated. The overall conversion efficiency (eta) of DSSCs is evaluated by the following items on the basis of the isolated dyes, including structures, absorption spectrum, energy gap, open-circuit voltage (V-oc), short-circuit current density (J(sc)), and reorganization energies (lambda(total)). After adsorbed on the TiO2 surface, the electron would be efficiently injected from dye into the TiO2 surface because of the increased of the lowest unoccupied molecular orbital (LUMO) energy level of the dyes, the decreased of the conduction band of TiO2 surface, and the narrowed band gaps for both dye and TiO2. Moreover, the injection times are in a reasonable range indicating that they are ideal dyes. Combination of all items, the performance of THI-2T-C (See Scheme 1, the sketch structures of all the investigated isolated dyes) stands out from the rest investigated dyes from the theoretical viewpoint. Only enlargement of the pi-linker extent is not a smart choice, since the nature of pi-linker plays a more important role in affecting the performance of DSSCs. (C) 2016 Elsevier B.V. All rights reserved.