| Sensitized solar cells (SSCs) as a kind of novel photovoltaic device have attracted considerable attention due to their low production cost, simple technique and high power conversion efficiency. Based on the working mechanism of SSCs, the interface contact between the sensitizer (dye or quantum dots) and semiconductor film, the structure of photoanode, and the electrochemical catalytic activity of counter electrode are important factors for the device performance. In the thesis, we designed and fabricated the photoanode and counter electrodes by different techniques to improve the interface contact inside the photoande and reduce the cost, and the major contents of the thesis is summarized as follows:(1) Y3Al5O12:Ce photoluminescent materials were fabricated by the co-precipitation method and used as an effectiv a marked improvement in conversion efficiency (7.91%) compared with the cell without a scattering layer (6.97%).(2) Graphene and grapnene/Au nanoparticles composite were fabr e scattering layer on the top of the transparent layer of nanocrystalline Tio2for dye sensitized solar cells (DSSCs). Due to enhanced light harvesting via the improved absorption of Y3Al5O12:Ce layer in the range of400-450nm, increased light scattering and reflection, and the light down-converting performance of Y3Al5O12:Ce particles, under one sun illumination (AM1.5G,100mW cm-2), the as-prepared DSSCs with Y3Al5O12:Ce scattering layer shows icated by microwave method, and then as-prepared samples were deposited onto graphite substrate by electrophoretic deposition (EPD) and used as counter electrodes for SSCs.1. Graphene-carbon nanotubes (CNTs) composite films with different amounts of CNTs were fabricated by EPD and used as counter electrodes of DSSCs. When CNTs are incorporated into the composite, the electrical conductivity of composite film is enhanced due to the good network structure for conductive bridge of the gaps between graphene nanosheets, leading to an improvement in performance of DSSCs. A maximum conversion efficiency of6.17%under one sun illumination (AM1.5G,100m Wcm-2) has been achieved for the cell based on graphene-CNTs counter electrode with60%CNTs, which has an improvement of70%and13%compared with the cells with pure graphene (3.63%) and CNTs (5.48%) counter electrodes, respectively.2. Graphene-Au nanoparticle composite film was fabricated by electrophoretic deposition and used as a counter electrode for CdS quantum dot-sensitized solar cells (QDSSCs). Under one sun illumination (AM1.5G,100mW cm-2), the cell with grapnene-Au counter electrode shows a energy conversion efficiency of1.36%, which is an increase of39%compared to the cell with pure graphene counter electrode (0.98%), due to a superior combination between highly catalytic Au nanoparticle and conductive graphene network structure. In the meantime, the value is also higher than those of the cells employing conventional Pt (1.21%) or Au (1.32%) counter electrodes.(3) CdS, CdSe, and CdS/CdSe quantum dots (QDs) sensitized TiO2films were fabricated by using microwave assisted chemical bath deposition (MACBD) technique and used as photoanodes for QDSSCs. Compared with conventional fabrication methods, this technique can synthesize QDs rapidly and suppress their surface defects as well as form a good contact between QDs and TiO2film, which can improve the performance of the cell. TiO2/CdS, TiO2/CdSe and TiO2/CdS/CdSe were one-step fabricated by MACBD technique and used as a photoanode for QDSSCs, respectively. Under one sun illumination (AM1.5G,100mWcm"2), conversion efficiencies of1.18%,1.75%,3.06%have been achieved for QDSSCs based on these electrode, which is comparable to those by using conventional fabrication methods. Compared with single (CdS and CdSe) QDs, their co-sensitized structure can provide a superior ability owing to the extension of light absorption range and effective charge injection from QDs to TiO2and thus exhibits a higher conversion efficiency.(4) The ZnO interface layer and ZnO/CdS electrode were fabricated by using ultrasonic spray pyrolysis (USP) deposition and applied in QDSSCs. 1. The ZnO interface layer was deposited on screen-printed TiO2layer by using USP technique. The formation of an inherent energy barrier between TiO2and CdS films and the passivation of surface traps on the TiO2film caused by the introduction of ZnO layer, which can improve the interface contact between TiO2and CdS, increase the adsorbed amount of CdS QDs and light scattering. Under one sun illumination (AM1.5G,100mWcm-2), a conversion efficiency of1.56%has been achieved for QDSSCs with ZnO interface layer, which has an increase of57%compared to the cell without a ZnO interface layer (0.99%).2. Sensitized-type solar cells based on ZnO photoanode and CdS QDs as sensitizers, in which both ZnO films and CdS QDs are prepared using USP technique. A good contact at the interfaces of FTO/ZnO/CdS has been formed by USP, which favors electron transportation and suppresses its recombination. Under one sun illumination (AM1.5G,100mWcm-2), a conversion efficiency of1.54%has been achieved for QDSSCs based on USP deposited ZnO/CdS electrode. |
