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Novel bifunctional aromatic linker utilized in CdSe quantum dots sensitized solar cell: boosting the open-circuit voltage and electron injection

Abstract

We have theoretically designed and characterized bifunctional aromatic linker PDTCA utilized in CdSe quantum dots sensitized solar cells, and further modified its benzene ring by varying both of the functional groups (NMe2, NH2, OMe, OH, Me, Cl, F, CN, NO2, and CF3) and sites (P1-P4). Via simulating the divided Interface-1 (TiO2/linker) and Interface-2 (linker/QDs), we find that the substituting on the P1 and P2 sites of PDTCA by most of these groups can outperform than that on the P3 and P4 site. On the one hand, it positively shifts the edge of unoccupied states of TiO2 toward vacuum level, favoring a large open-circuit voltage (Voc). On the other hand, it red-shifts the maximum absorption peak (λmax) toward low-energy region, and lessens the hole delocalization from linker to QDs, weakening the electron-hole recombination. As a whole, the TiO2/linker/CdSe QDs system belongs to the type-II energy level alignment, and the edges of occupied and unoccupied states of QDs are insensitive to the variation both of the groups and sites. After excluding the undesired P3 and P4 sites, the electron injection efficiency (ηinj) in the screened groups containing NH2, Cl, CN, and NO2 based TiO2/linker/CdSe QDs systems are calculated. The result denotes that CN associated systems yields almost complete electron injection (ηinj ~99%) no matter what the functional site is compared to the picture before substituting (57%). Whereas NH2, Cl, and NO2 contained systems produce a site dependent ηinj pronouncedly. This is attributed to the overwhelming injection rate constant (kinj) than recombination rate constant (krec) (1013 vs. 1010 s-1) in CN capped interfaces, whereas in Cl, NH2, and NO2 related systems, the considerable and even larger krec with regard to kinj suppresses the efficient injection. Finally, the CN(P1)-PDTCA and CN(P2)-PDTCA are screened out as the most desired candidates for future application due to their performances favoring large Voc, lessening recombination, red-shift λmax, and boosting electron injection.

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Publication details

The article was received on 18 Apr 2017, accepted on 11 Jun 2017 and first published on 12 Jun 2017


Article type: Paper
DOI: 10.1039/C7TA03349D
Citation: J. Mater. Chem. A, 2017, Accepted Manuscript
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    Novel bifunctional aromatic linker utilized in CdSe quantum dots sensitized solar cell: boosting the open-circuit voltage and electron injection

    W. Ding, X. Peng, Z. Sun and Z. Li, J. Mater. Chem. A, 2017, Accepted Manuscript , DOI: 10.1039/C7TA03349D

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