Interface Modification After Dye-adsorption&Composite Sensitization And Their Photovoltaic Properties

Dye-sensitized solar cells （DSCs） is an important research field of clean energysources. Inerface modification and composite sensitization are important approaches toimprove the performance of DSCs. In this paper, to solve some key problems such asdye aggregation, energy level matching between dye and photoanode, electron injectionand recombination at the interface of photoanode/dye/electrolyte, we mainly researchedinterface modification after dye-adsorption. Furthermore, using interface modificationmaterials as interlayer, alternating assembled structure for composite sensitization wasfabricated. The research is focused on the interaction between interface modificationmaterials and dye molecules and their effects on the photovoltaic properties of DSCs.The main results and conclusions of this dissertation are as follows:（1） The materials and methods for interface modification after dye-adsorption havebeen investigated. We used TBP for interface modification after dye-adsorption, insteadof adding it in the electrolyte as usual. It can be seen in the FTIR that TBP retarded thedye aggregation. Results of EIS indicated that TBP could reduce the chargerecombination. Furthermore, using TBP for interface modification could strengthenedthe effect of reducing charge recombination and avoid the disadvantage of blockingcharge diffusion in the electrolyte at the same time. As a result, a higher enhancement ofDSCs’ conversion efficiency by using TBP for interface modification afterdye-adsorption has been obtained. However, the interaction between TBP and N3dyemolecules decreased the LUMO of N3, resulting in the decrease of electron injectionefficiency, which could cause the reducing of photocurrent.（2） We studied the effects of Mg（OAc）₂inferface modification after dye-adsorptionfor the first time. Results of FTIR and CV represented that interaction betweenMg（OAc）₂and N3dye could retard the dye aggregation and charge recombination.Furthermore, the interaction also shifted the LUMO of N3to a higher level, whichenhanced the electron injection efficiency. As a result, Mg（OAc）₂inferface modificationafter dye-adsorption remarkably improved the efficiency and stability of DSCs.（3） As the interface modification materials of Mg（OAc）₂and TBP improve theperformance of DSCs through only retarding the dye aggregation and charge recombination, a multifunction interface modification material,8-hydroxyquinolinealuminium （Alq₃） has been developed and applied in the interface modification afterdye-adsorption. Fisrtly, it retarded the charge recombination, shown in the EIS and darkcurrent curve. Secondly, it transferred energy to N3dye through F rster resonanceenergy transfer （FRET）, enhancing the photo-resoponse of DSCs.（4） The interlayer of alternating assembled structure has been studied using acompact TiO₂film as a simplified model for the TiO₂porous film. Based on Al₂O₃interlayer, N3/Al₂O₃/N3alternating structure has been fabricated. This structureincreased light absorption, improved the interface charge transfer, retarded thecharge recombination and then enhanced the conversion efficiency. To furtherwiden photoresponse range, the N3/Al₂O₃/N749alternating assemble structure hasbeen fabricated. Compared to the devices using individual dye, such structure increasedthe conversion efficiency and reduced the charge recombination. Based on results ofEIS, a series of equivalent circuit models were built to explain electron process and thechange of parameters of DSCs. The value of impedance elements obtained bycalculation from the equivalent circuit models accorded with the measured values well.