Research Of Photoelectric Properties Of Miconductor Thin Film Solar Cells By Incorporating Plasmonic Gold Nanoparticles

Semiconductor thin film solar cells are given extensive attention and get rapid developmentdue to their easy processing and low cost. However, their photoelectric conversion efficiency isrelatively low. A novel and effective method for enhancing light harvesting or trapping todevelop high-efficiency photovoltaic devices is the mergence of metallic nanostructures thatsupport surface plasmons. Based on this theory, we design different semiconductor thin filmanode structure with plasmonic gold nanoparticles and test their photoelectric performance inorder to obtain the optimal performance of semiconductor thin film solar cells. The work in thisthesis can be summarized as follows:1. Three-dimensional porous CdSe films mergenced with the plasmonic goldnanoparticles (ITO/Au/CdSe) were fabricated in a simple electrodeposition process. A prominentenhancement in light absorption of CdSe films was attained by the efficient light scattering ofgold plasmons as subwavelength antennas and concentrators. With an appropriate size andsuitable distance between the gold nanoparticles, the local near-field enhancement in theproximity of gold nanoparticles, which is associated with the surface plasmon (SP) excitationinduced by visible light irradiation, can also favor carrier generation and separation and increasephotocurrents when the gold plasmons couple with the neighboring CdSe films and transfer theplasmonic energy from the metal to the CdSe films. Photoelectric performance test results showthat when the deposition time of gold plasmons is300s, the ITO/Au300/CdSe composite filmexhibits the highest photocurrent and open-circuit voltage among the tested samples. On thebasic of ITO/Au300/CdSe, the multilayer ITO/(Au300/CdSe)n(including n=1,2,3,4,5) structureswere constructed, and their microstructures, absorption and photoelectric properties were tested.The results show that the photoelectric performance of porous Au/CdSe composite films washighly tunable with respect to the number of Au/CdSe bilayer. The optimal photocurrent andphotovoltage are obtained in the ITO/(Au300/CdSe)4system because the thicker absorber layerwith less porous structure might limit the electrolyte diffusion into the hybrid electrode andimpose a barrier for electron tunneling and transferring.2. The CdS quantum dot-sensitized TiO2films with plasmonic gold nanoparticles weredesigned on FTO conductive glass as photoanodes by the electrodeposition of gold combinedwith the“successive ionic layer adsorption and reaction”(SILAR) method for CdS deposition onporous TiO2films. The effect of the position of gold nanoparticles in the composite films on the photoelectric performance was studied. Photoelectric performance test results show that theFTO/Au/TiO2/CdS composite films exhibits a prominent enhancement in light absorption and thehighest photocurrent and open-circuit voltage by efficient light scattering of gold plasmons assub-wavelength antennas and concentrators. The photogenerated electron formed in thenear-surface region of TiO2and CdS is facilitated to transfer to the plasmonic gold, resulting inthe enhancement of photocurrent and incident photon-to-current conversion efficiency of hybridphotoanode upon photoirradiation. Furthermore, the photovoltaic response of hybrid is highlytunable with respect to the number of SILAR cycles applied to deposit CdS. The microstructures,absorption and photoelectric properties of different structures with different number of SILARcycles were investigated. The results show that the thickness and absorption intensity of differentstructures increase with the increasing the number of SILAR cycles, and the photoelectricproperties measurement indicates that the optimal short-circuit current and open-circuit potentialare obtained when the number of SILAR cycle is7. The thicker CdS layer with less porousstructure and larger CdS crystals might limit the electrolyte diffusion into the hybrid electrodeand impose a barrier for electron tunneling and transferring.3. One-dimensional TiO2nanorods array were prepared on FTO conductive glass by asimple hydrothermal method. The effect of the concentration of hydrochloric acid on TiO2nanorods morphology was studied. SEM images show that a regular arrangement andhomogeneous density of TiO2nanorods array is obtained when the concentration of hydrochloricacid of7.0mol/L. And then gold nanoparticles and CdSe quantum dots were depositedsuccessively on the TiO2nanorods array to prepare the FTO/TiO2(NR)/Au/CdSe composite filmswith the films without gold nanoparticles (FTO/TiO2(NR)/CdSe) as the reference. Weinvestigated their absorption spectrum and photoelectric response. The results show that theFTO/TiO2(NR)/Au/CdSe composite films have a higher absorption, enhanced photocurrentdensity and higher photovoltage by the mergence of plasmonic gold nanoparticles.