Study Of The Photovoltaic Properties Of Quantum Dot Sensitized Solar Cells Decorated With Hollow Gold Nanospheres

Quantum dot sensitized solar cells are given great attention due to their low cost and simple preparation procedure. However, the actual conversion efficiency of solar cells is still low. Recently, great efforts have been carried out to improve the conversion efficiency of solar cells. The surface plasmons(SPs) effect induced by metal nanoparticles is an effective approach to solve this challenge since plasmonic construction can improve the absorption ability for sunlight and photovoltaic properties of solar cells. In this thesis, the hollow gold nanospheres(HGNs) are fabricated and applied to solar cells. The effect of HGNs’ size on photoelectric properties of cells is studied. We optimize the design of photoanodes’ structures to gain the best photoelectric performance of solar cells. The main contents are as follows:1. The HGNs are synthesized by a sacrificial template method, and are further electrophoretic deposited on the surface of TiO2 nanorods(NRs) prepared by the hydrothermal method, then a TiO2NR/HGN/CdS composite photoanode is prepared when the photosensitive CdS is deposited on the surface of TiO2NR/HGN surface by the successive ionic layer adsorption and reaction(SILAR) method. Adding a certain concentration of HGN into photoanode can effectively increase the ability of potoanode’s light absorption, which increases the capacity of optical coupling of photosensitive CdS materials around them and promotes more carriers generation to enchance the photoelectric properties of photoanodes. The photovoltaic performance of photoanodes is highly depentend on the concentration of plasmoinc HGN and the quantities of photosensitive CdS. The results incidate that when the electrophoretic deposition time of HGN is 7min, the TiO2NR/HGN/CdS photoanode has the optimal photocurrent density、open circuit voltage and incident photon-electron conversion efficiency among all the test samples. When the number of SILAR of photosensitive CdS is 4 times, we obtain the optimal photoanode structure to absorb the photons to generate more carriers.2. The different sizes of HGNs between 20 and 60 nm are prepared by sacrificial template method. We add these HGNs into quantum dot-sensitized solar cells to study the effect of SPR on photovoltaic properties. Firstly, the TiO2NR/HGN/CdSe/ZnS composite photoanode is fabricated by the combination of hydrothermal method, electrophoretic deposition, chemical bath deposition(CBD) and SILAR method. Secondly, we prepare the FTO/CuS electrode as to be the cathode for solar cells. The results indicate that the absorption peak of HGN caused by SPR has a redshift and a wider response in visible region compared to that of SGN when the two metal nanoparticles have the same size and mass fraction. The solar cells have a better light trapping ability when adding the HGN into the cells, and the energy conversion efficiency is also improved by 20%. When the outer diameter of HGNs is about 33 nm, the better photovoltaic performance of solar cells is obtained, which is attributed to the optimal match between the SPR absorption peak and the light absorption peak of photoanode material. The ZnS layer in the photoanode can protect the photosensitive CdSe material from photocorrosion, favoring the cells best photoelectric properties. The effects of HGNs concerntation and CdSe quantities on the photovoltaic properties of solar cells are further investigated, respectively. The results indicate that when the mass fraction of HGNs is 1.33wt%, the energy conversion efficieny rises up to be 3.08%. The excess quantities of HGNs as composite center will reduce the concentration of carriers. When the deposited time of CdSe is 15 min, the photoanodes have the optimal thickness of photosensitive CdSe material, and the efficiency of the whole solar cell is therefore optimal. At last, we try to design the FTO/CuS cathode, and the optimal electrical activity of FTO/CuS electrode can be confirmed when the pH value of the system is 2.69, The FTO/CuS electrode is more suitable as the cathode of quantum dot-sensitized solar cells comparing with Pt electrode.3. The branched TiO2 nanorods(TiO2BNRs) are prepared by a seeding method and second hydrothermal growth step, then the TiO2BNR/HGN/CdSe/ZnS photoanode is builded by the combination of electrophoretic deposition, CBD and SILAR method. The FTO/CuS electrode is used as the cathode of cells. The hierarchical nanostructures of TiO2 and the SPR of HGN can improve the photovoltaic performance of solar cells together. Our results incidate that when the time of growing seed is 1h, the surface of TiO2 NRs is modified by needle-like seeds with jagged circular cross-section. Then successive hydrothermal growth of TiO2 NRs results in omnidirectional growth of nanobranches with the length region of 30-160 nm. When the length is 30 nm,the energy conversion efficiency of solar cells rises up to 3.26%, which indicates that HGN as scatter center can promote the generation of carrier at the same time.