High Performance Quantum Dot-sensitized Solar Cells Based On TiO₂ Nanorod Arrays

As a promising new-type solar cells,quantum dot-sensitized solar cell?QDSC?hasreceived tremendous attention for its remarkable theoretical power conversion efficiency.One dimensional?1D?TiO₂ nanorod arrays?TNAs?can offer direct charge transport channels in view of their excellent radial charge transport characteristics,so as to reduce interface charge recombination in solar de vices.Therefore,the use of TNAs as electron transporters is expected to significantly improve the photovoltaic performance of QDSCs.In Chapter 2,1D TNAs have been synthesized through hydrothermal method,and the morphology,structure and optical properties has been systematically studied.Theresults show that the as-synthesized TNAs exhibit rutile phase structure and single-crystalline feature;moreover,the corresponding nanorod length can be readily by controlling the hydrothermal reaction time.In Chapter 3,we studied the photovoltaic performance of CdS/CdSe quantum dots?QDs?co-sensitized TNA solar cells.The in-situ deposited CdS and CdSe QDs were prepared on the TNAsthrough successive ionic layer adsorption and reaction?SILAR?and chemical bath deposition?CBD?methods,respectively.It is found that the QDsare uniformly loaded on the surface of TNA with high coverage.The UV-vis absorption spectrum and electrochemical impedance spectroscopy?EIS?characterizations reveal that,with the increase of nanorod length,the amount of loaded QDs is lowed while the interfacial charge recombination is accelerated.Eventually,a power conversion efficiency?PCE?up to 3.57% has been achieved for QDSCs based on the 1.7 ?m TNAs through the optimization of nanorod length.Furthermore,benefiting from highly efficient charge transport and charge collection properties in view of the excellent 1D radial charge transport channels and favorable Q D loading,the TNAs-based QDSC yield an extremely high open-circuit voltage?Voc?of 0.77 V,which is the highest value of Voc for TiO₂-based QDSCs,to the best of our knowdge.In Chapter 4,we constructed an efficient wide spectral responsive PbS QDSC based on TNAs.The results show that PbS QDs broaded the light absorption range of QDSCs to near infrared region,thereby contributing to the improvement of photocurrents of QDSC.Meanwile,the fill factor?FF?of TNA-based QDSC receives appreciable improvement compared to the conventional TiO₂ nanoparticle-based devices;the reason mainly relies on the suppressed interfacial charge recombination as a result of the excellent radial charge transport through TN As.The as-obtained TNA-based PbS QDSC yields a PCE of 1.15%,along with a high FF of 0.51.