Enhanced Photovoltaic Performance Of Dye-sensitized Solar Cells By Electrode Optimization And Interfacial Modification

Dye-sensitized solar cells?DSSCs?have attracted much attention due to their low cost,easy fabrication proceduresand high theoreticalconversion efficiency.In this paper,the research work focuses on electrode optimization andinterfacial modification,especially on the improvement of light harvesting,charge separation and transport in DSSCs,so as to enhance the conversion efficiency of DSSCs.The structure,morphology,electrochemical properties of electrodes and the photovoltaic properties of device were characterized to deeply understand the working mechanisms of DSSCs.The main research results are as follows: 1.Research on TiO₂ photoanode for DSSCsRare-earth doped up/down-conversion materials(ZnO:Er³⁺,Yb³⁺,Li⁺,ZnO:Eu³⁺,Tb³⁺)were synthesized and used to prepare ZnO:Eu³⁺,Tb³⁺/TiO₂:ZnO:Er³⁺,Yb³⁺,Li⁺ compositephotoanode for DSSCs.In such a composite structure,the ultraviolet and near infrared radiation could be converted to visible emission by downconversion and upconversion luminescence process,respectively.Thus,the light harvesting efficiency and photocurrent in DSSCs will be enhanced,and the short-circuit current density and conversion efficiency of the DSSCs reached to the optimal values: 10.13 mA/cm2 and 4.48%.P25:Ag NWs@TiO₂ composite materials were prepared for the introduction into photoanodes of DSSCs.In this composite structure,Ag NWs@TiO₂ can effectively accelerate electron separation and transport as well as enhance the light scattering capabilities of photoanodes due to its one-dimensional structure and high electrical conductivity.And DSSCs assembled with 0.2 wt% Ag NWs@TiO₂ exhibit better performance than that of the devices based on pure P25,showing an optimal conversion efficiency of 6.81%.2.Research on counter electrode for DSSCsNiS and NiS-H₃Mo₁₂O₄₀P(PMo₁₂)composite films were fabricated on transparent conductive glass?FTO?by periodic potential reversal method and were used as counter electrode for DSSCs.Compared to NiS electrode,NiS-PMo₁₂ composite structure has higher electrocatalytic ability for I3-reduction.And the conversion efficiency of DSSCs based on NiS-PMo₁₂ is 6.45%,which is comparable to that of Pt-DSSCs.The results show that NiSPMo₁₂ composite structure can replace Pt as counter electrode for DSSCs.3.Interfacial modification for DSSCsTiO₂ compact layer was deposited on FTO and H₃PW₁₂O₄₀(PW₁₂)is prepared as an interfacial layer between FTO and TiO₂ compact layer of DSSCs.The results show that the introduced interfacial layer could block the direct contact of electrolyte with conductive substrate,so as to reduce the charge recombination in DSSCs.And the PW12 layer can accept the electrons from the conductive band?CB?of TiO₂ to reduce the electrons trapped in Ti O₂ and promote charge transfer.The solar cells with FTO/PW₁₂/Ti O₂ exhibited conversion efficiency of 9.3%,which were higher than those of DSSCs without TiO₂ compact layer and PW₁₂ interfacial layer.NiO and NiO:Eu³⁺,Tb³⁺ films were deposited on porous TiO₂ layer by a sol-gel spincoating method as the photoanodes of DSSCs.The TiO₂/NiO and TiO₂/NiO:Eu³⁺,Tb³⁺ structure could block the direct contact between porous TiO₂ layer and oxidized dye or electrolyte,so as to reduce the charge recombination at TiO₂/dye/electrolyte interface.And pn junction formed by n-type TiO₂ and p-type NiO,NiO:Eu³⁺,Tb³⁺ can promote carrier separation.The research results show that the photovoltaic performance of device with TiO₂/NiO:Eu³⁺,Tb³⁺ is better than that with TiO₂,exhibiting a high conversion efficiency of 8.8%.