CdS Quantum Dot-sensitized Vertical TiO₂ Nanorod Arrays By A Linker-assisted SILAR Method

Energy is the driving force behind economic development and the basis of modern civilization. As one of the third-generation solar cells, quantum dot-sensitized solar cells(QDSSCs) have been developed rapidlyand extensively in recent years because of their unique optical and electronic properties, such as tunable band gap, high extinction coefficients, and multiple excitons generation effects. However, QDSSC still shows relative lowphotovoltaic efficiency at present(much less than thetheoretical thermodynamic efficiency 44%). The interfacial contact of QDs and TiO2 nanostructure in QDSSC is crucial for the charge transfer efficiency. For improvement of the interfacial contact, the homogeneous dispersion of QDs on the surface of TiO2 nanostructure has been considered as one major challenge in QDSSC.Combining organicshort-chain ligand(TGA) with the traditional successive ionic layer adsorption and reaction(SILAR), is an effective method to meet this challenge.In this paper, one-dimensional TiO2-basedphotoanode prepared by a simple hydrothermal method and TiO2 nanoparticle film prepared by screen-print methodarestudied.The influence of TGA on the electrochemical performance of QDSSCis evaluated through UV–vis absorbance spectroscopy, current–voltage performance(I-V curve), photoelectric stability(OCV curve) and electrochemical impedance spectroscopy(EIS) methods. The performance of TiO2 nanostructureQDSSC and QDSSC prepared through linker-assisted SILAR technologyis investigated in this paper and the following results can be obtained in the paper.(1) Theone-dimensional TiO2-basedphotoanode prepared by a simple hydrothermal method and TiO2 nanoparticle film prepared by screen-print methodon FTO glass isstudied.The effect of tetrabutyl titanate(TBOT) on the TiO2 nanorod film structure is discussed.The optimal process parameters(1.5 mL)based on different characterizationsof QDSSCs are determined through the different characterizations and measurements,such as FSEM, XRD, UV-vis and photoelectric performance test.(2) The homogeneous dispersion of QDs on the surface of TiO2 nanostructure is prepared by a low-cost, simple and effectivelinker-assisted SILAR method.The research finds out that the SILAR method using TGA linker can prepare homogeneously dispersed CdS on vertical TiO2 nanorods arrays, which can improve the performance of QDSSC effectively.The results show that the TGA ligand can act as an efficient bridge between CdS QDs and TiO2, whilethe content and particlesize of the QDs can be easily tuned by controlling the dipping time and SILAR cycle.(3) Thephotoelectric performance ofCdS quantum dots sensitized TiO2 nanocrystalline photoanodes is evaluated, such as UV-vis, I-V curves, OCV curve and EIS performance, to explore the effect of the properties of QDSSC. The factors affecting the performance are also studied,such as the TiO2 nanocrystalline films preparation, quantum dots deposition, polysulfide electrolyte preparation and cell assembly process. QDSSC with TGA exchange treatments shows 0.529 V open circuit potential, 3.19 mA/cm2 short circuits current and 6.8-times conversion efficiency more than before.