Performance Of Solar Cells Co-Sensitized By Green Sulfide Quantum Dots And N719 Dye

Dye-sensitized solar cells are promising photovoltaic devices,which have the advantages of simple preparation process,low cost,low energy consumption and high photoelectric conversion efficiency.However,its photoelectric conversion efficiency is still low compared with monocrystalline silicon or perovskite solar cells,because of the shortcomings of narrow absorption spectrum and low molar extinction coefficient of dyes,resulting in low solar spectral utilization efficiency.Inorganic quantum dots have excellent photoelectric properties such as high molar extinction coefficient and wide absorption spectrum.Therefore,in this paper,the advantages of the two are combined.Green inorganic quantum dots Ag₂S or Bi₂S₃ and N719 dye are used as composite photosensitizers to co-sensitize thin film solar cells.By expanding the spectral response range and intensity of photosensitizers,the photoelectric conversion efficiency of the cells is expected to be improved.Multilayer Ag₂S or Bi₂S₃ quantum dots were synthesized via the successive ionic layer adsorption and reaction route on Ti O₂ photoanode,and realize common sensitization with N719 dye by immersion adsorption method,and assembled with electrolyte and counter electrode to form a battery device.The microstructure and electrochemical properties of the materials and devices were characterized by XRD,EDS,SEM,TEM,UV-vis diffuse reflectance spectroscopy and electrochemical impedance spectroscopy.The results show that the introduction of quantum dots can enhance charge transfer and effectively inhibit electron-hole recombination.Under the irradiation of AM 1.5（100 m W/cm~2）xenon lamp,the co-sensitized solar cell sample deposited with four Ag₂S quantum dots showed the best performance:the photocurrent density was 10.99 m A/cm~2,and the photoelectric conversion efficiency was 4.82%.The solar cells deposited with two layers of Bi₂S₃ quantum dots have the best performance in the series of samples,with photocurrent density of 10.76 m A/cm~2 and photoelectric conversion efficiency of 4.7%,which are significantly higher than those sensitized only by N719（8.35 m A/cm~2 and 3.35%）under the same conditions.Compared with Ag₂S quantum dots(particle size of about 10^-9m),Bi₂S₃ quantum dots have a larger particle size range,which is distributed in the range of about10^-8-10^-10m.Therefore,we conclude that:Green Ag₂S QDs or Bi₂S₃ QDs with N719 sensitized solar cell can enhance the solar spectrum absorption and suppress electronic-hole compound,is an effective strategy to improve the efficiency of solar cells,the number of quantum dots（deposits）and the particle size and its energy level matching degree of composite with N719 photosensitizer were sensitized solar cells had a greater influence on the photovoltaic performance.