Performance Research Of Sensitized Solar Cell

Since the21st century, dye-sensitized solar cell (DSSC) is becoming one of the most promising solar photovoltaic products because of its simple process and low cost. In order to further reduce its cost and improve its stability, people use inorganic semiconductor quantum dot to replace the organic dye sensitizer and produce the quantum-dot sensitized solar cell (QDSC). Its special characteristics make it to be a hot research topic in the photovoltaic field. This paper’s contents mainly study four aspects:(1) Research of DSSC based on TiO2nanoparticle porous photoanode. TiO2nanoparticle powder was obtained by sol-gel process, then, the TiO2nanoparticle powder was mixed with terpilenol, ethyl cellulose and some other organic additive to make the paste for screen printing. The TiO2nanoparticle porous films with different thickness were prepared through screen printing by controlling the printing times. The structure and morphology characteristics of TiO2nanoparticle powder and the film obtained by screen printing have been analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM). The results showed that the TiO2nanoparticle was anatase phase structure and the particle size was about30nm and the TiO2particle was well-distributed and formed a porous structure in the film. After sensitization, the dye-covered TiO2nanoparticle porous electrode with different thickness,I-/I3-electrolyte and Pt counter electrode were assembled to be DSSCs. The photovoltaic performance、electron transport and recombination of DSSC were investigated by J-V characteristic、incident photo-to-current conversion efficiency (IPCE)、electrochemical impedance spectroscopy (EIS) and intensity modulation photocurrent spectroscopy/intensity modulation voltage spectroscopy (IMPS/IMVS) test. The results showed that the light-to-electricity efficiency(η) of DSSC increased from3.78%to5.75%, the electron transport time(τt) in the photoanode increased from2.33ms to8.95ms and diffusion coefficient (Dn) from4.57×10-5cm2/s to14.74×10-5cm2/s with the thickness of the TiO2nanoparticle porous photoanode increased from5μm to14μm. The electron transport, recombination and collection process of DSSC competed and restricted with each other. The electron collection and η of cells were influenced by the electron diffusion ability. The electron lifetime (τn) and Dn was influenced the trap/detrap process of the surface state and trap state. The transportation and recombination of photoelectron competed each other which would impact the collection rate of photoelectron.(2) Research of DSSC performance based on TiO2nanoparticle/TiO2nanowire composite photoanode. The TiO2nanoparticle powder and TiO2nanowire powder were obtained by sol-gel process and hydrothermal method, respectively. Then, mixed these two powders with different ratio and prepared the paste for screen printing. The TiO2nanoparticle/TiO2nanowire composite film with14um thick was obtained by screen printing. After sensitization, the composite photoanode was assembled to be DSSC with I-/I3-electrolyte and Pt counter electrode. The effect of TiO2nanoparticle/TiO2nanowire ratio on the photovoltaic performance, electron transport and recombination of DSSC were investigated by J-V characteristic, IPCE. EIS and IMPS/IMVS test. The results showed that the η was first fell then rose and express the highest value of2.77%, the τt, and τn first increased then decreased with the TiO2nanowire ratio increased. When the TiO2nanowire ratio increased from50%to75%, the τt, decreased but Dn increased. But when the TiO2nanowire ratio increased from25%to50%, the τt increased and Dn decreased.(3) Research of QDSC performance based on TiO2nanowire arrays sensitized by CdS quantum dot. TiO2nanowire arrays on transparent conductive fluorine-doped tin oxide (FTO) substrates was prepared by hydrothermal synthesis method using the precursors of hydrochloric acid, deionized water and tetrabutyl titanate. The CdS quantum dot sensitized TiO2nanowire arrays photoanode was prepared by successive ionic layer adsorption and reaction technique. Then the photoanode was assembled to be QDSC with I-/I3-electrolyte and Pt counter electrode. The influence of sensitized cycles on the photovoltaic performance and electron transport of QDSC were studied. The results showed that, with the increase of sensitized cycles, the size and density of the CdS quantum dot increase, the η first increased then fell, for the cell assembled with15sensitized cycles showed the best photovoltaic performance, the short circuit current density is0.61mA/cm2, open circuit voltage0.65V, fill factor0.50, and photoconversion efficiency0.20%, Dn and t, are3.20×10-6cm2/s and2.10×10-2s respectively.(4) Research of QDSC performance based on TiO2nanoparticle porous photoanode sensitized by CdS quantum dot. We successively study the influence of the TiO2nanoparticle porous film and CdS quantum dot sensitized cycles to the photovoltaic performance. Then the performance of QDSC assembled by S27Sx-and I-/I3-electrolyte was compared. The results showed that optimum thickness of TiO2nanoparticle porous film is14μm; the best CdS quantum sensitized cycle is20times. The QDSC assembled by S2-/Sx-electrolyte had better stability than the QDSC assembled by I-/I3-electrolyte, but the fill factor was lower than the QDSC assembled by I-/I3-electrolyte because the weak catalyze ability of Pt to the reaction of S2-with electron and the whole unsatisfactory performance of S2-/Sx-electrolyte. Because of these, the photovoltaic performance was been restricted.