Effect of linkers with different chemical structures on photovoltaic performance of CdSe quantum dot-sensitized solar cells
Introducing bifunctional linkers (COOH-R-SH) between TiO 2 electrodes and quantum dots (QDs) was an effective apprIntroducing bifunctional linkers (COOH-R-SH) between TiO 2 electrodes and quantum dots (QDs) was an effective approach in preparation of quantum dot-sensitized solar cells (QDSCs). Three types of linkers (4-mercaptobenzoic acid (MBA, R =phenyl), 3-thiophenecarboxylic acid (TPA, R =thiophene), and thioglycolic acid (TGA, R =alkyl)) were used to functionalize TiO 2 electrodes and prepare TiO 2 /CdSe QDSCs with photoelectric conversion efficiency (PCE) of 5.50%, 4.59% and 4.85%, respectively. Various properties of modified and blank TiO 2 electrodes, such as QDs loading, absorbance, work function, interfacial charge injection, recombination and their influence on PCE were investigated. In spite of low adsorption amounts of MBA on TiO 2 , the phenyl MBA-TiO 2 electrodes obtained the highest Cd content due to regular arrangement and strong affinity to QDs. The FTIR spectra proved strong interactions between MBA and TiO 2 electrodes, leading to fast electron injection from QDs to TiO 2 electrodes. The electron injection rate in MBA-TiO 2 electrodes was the same as blank-TiO 2 , larger than TGA- and TPA-ones. Work function of TiO 2 electrodes modified by linkers could reduce several eV , in which the MBA-one decreased less, corresponding to the highest applied potential difference. The open-circuit voltage-decay measurement demonstrated that the MBA-TiO 2 photoanodes had the least charge recombination. Enhanced light absorption capacity and fast electron injection rate were two key points for modified cell to improve short-circuit current, while low recombination and appropriate energy level positions increased open-circuit voltage. Those make MBA-TiO 2 photoanodes obtain the best efficiency of 5.50%. We expected this work to guide the selection of linkers for design and optimization of photoanodes interface of QDSCs.oach in preparation of quantum dot-sensitized solar cells (QDSCs). Three types of linkers (4-mercaptobenzoic acid (MBA, R =phenyl), 3-thiophenecarboxylic acid (TPA, R =thiophene), and thioglycolic acid (TGA, R =alkyl)) were used to functionalize TiO 2 electrodes and prepare TiO 2 /CdSe QDSCs with photoelectric conversion efficiency (PCE) of 5.50%, 4.59% and 4.85%, respectively. Various properties of modified and blank TiO 2 electrodes, such as QDs loading, absorbance, work function, interfacial charge injection, recombination and their influence on PCE were investigated. In spite of low adsorption amounts of MBA on TiO 2 , the phenyl MBA-TiO 2 electrodes obtained the highest Cd content due to regular arrangement and strong affinity to QDs. The FTIR spectra proved strong interactions between MBA and TiO 2 electrodes, leading to fast electron injection from QDs to TiO 2 electrodes. The electron injection rate in MBA-TiO 2 electrodes was the same as blank-TiO 2 , larger than TGA- and TPA-ones. Work function of TiO 2 electrodes modified by linkers could reduce several eV , in which the MBA-one decreased less, corresponding to the highest applied potential difference. The open-circuit voltage-decay measurement demonstrated that the MBA-TiO 2 photoanodes had the least charge recombination. Enhanced light absorption capacity and fast electron injection rate were two key points for modified cell to improve short-circuit current, while low recombination and appropriate energy level positions increased open-circuit voltage. Those make MBA-TiO 2 photoanodes obtain the best efficiency of 5.50%. We expected this work to guide the selection of linkers for design and optimization of photoanodes interface of QDSCs.
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