title: The Role of Porphyrin-Free-Base in the Electronic Structures and Related Properties of N-Fused Carbazole-Zinc Porphyrin Dye Sensitizers.
abstract: Dye sensitizers can significantly affect power conversion efficiency of dye-sensitized solar cells (DSSCs). Porphyrin-based dyes are promising sensitizers due to their performances in DSSCs. Here, based upon a N-fused carbazole-zinc porphyrin-free-base porphyrin triad containing an ethynyl-linkage (coded as DTBC), the novel porphyrin dyes named DTBC-MP and DTBC-TP were designed by varying the porphyrin-free-base units in the π conjugation of DTBC in order to study the effect of porphyrin-free-base in the modification of electronic structures and related properties. The calculated results indicate that, the extension of the conjugate bridge with the porphyrin-free-base unit results in elevation of the highest occupied molecular orbital (HOMO) energies, decrease of the lowest unoccupied molecular orbital (LUMO) energies, reduction of the HOMO-LUMO gap, red-shift of the absorption bands, and enhancement of the absorbance. The free energy changes demonstrate that introducing more porphyrin-free-base units in the conjugate bridge induces a faster rate of electron injection. The transition properties and molecular orbital characters suggest that the different transition properties might lead to a different electron injection mechanism. In terms of electronic structure, absorption spectra, light harvesting capability, and free energy changes, the designed DTBC-TP is a promising candidate dye sensitizer for DSSCs.
authors.affiliation: Department of Applied Physics, Lanzhou University of Technology, Lanzhou 730050, China. lixingy@aliyun.com.
authors.forename: Xing-Yu
authors.initials: XY
authors.lastname: Li
authors.affiliation: Department of Applied Physics, Lanzhou University of Technology, Lanzhou 730050, China. zhcrxy@lut.cn.|State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China. zhcrxy@lut.cn.
authors.forename: Cai-Rong
authors.initials: CR
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China. youzhiwu@lut.cn.
authors.forename: You-Zhi
authors.initials: YZ
authors.lastname: Wu
authors.affiliation: Department of Applied Physics, Lanzhou University of Technology, Lanzhou 730050, China. zhhm@lut.cn.
authors.forename: Hai-Min
authors.initials: HM
authors.lastname: Zhang
authors.affiliation: Department of Applied Physics, Lanzhou University of Technology, Lanzhou 730050, China. wwei@lut.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Applied Physics, Lanzhou University of Technology, Lanzhou 730050, China. yuanlh@lut.cn.
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Yuan
authors.affiliation: Department of Applied Physics, Lanzhou University of Technology, Lanzhou 730050, China. hyang@lut.cn.
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Physics, Lanzhou City University, Lanzhou 730070, China. lzj@lzcu.edu.cn.
authors.forename: Zi-Jiang
authors.initials: ZJ
authors.lastname: Liu
authors.affiliation: College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China. chenhs@nwnu.edu.cn.
authors.forename: Hong-Shan
authors.initials: HS
authors.lastname: Chen
mesh_terms: D002227:Carbazoles / Q000737:chemistry*; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D008962:Models, Theoretical
chemical_list: D002227:Carbazoles; D008665:Metalloporphyrins; C041514:carbazole; C017802:zinc hematoporphyrin
keywords: density functional theory; dye sensitizers; electronic structures; excited state; porphyrin derivatives