Study On The Construction And Photoelectric Conversion Efficiency Of Dye Sensitized Solar Cells Based On SnO₂

As a typical representative of the third generation of solar cells,dye-sensitized solar cells?DSSCs?have been extensively studied because of their low cost,simple process and high theoretical photoelectric conversion efficiency.Since 1991,Professor Michael Gr?tzel has reported a cheap,high-efficiency titanium dioxide?TiO₂?colloidal solar cells with a photoelectric conversion efficiency of 7.1%on Nature,a great breakthrough has been made in less than 30 years.Now the efficiency has exceeded14%.At present,the most commonly used photoanode material is TiO₂,but its electron mobility is low,which affects the transmission rate of photogenerated electrons,thus increasing the probability of electronic recombination reaction and affecting the performance of DSSCs.Based on this,tin dioxide?SnO₂?which is similar to the structure of TiO₂ and has faster electron mobility was chosen as the photoanode material in this paper.The pure SnO₂ photoanode was improved by adding scattering layer?SL?,alumina layer?Al₂O₃?and ion doping.The photoelectric conversion efficiency of SnO₂ photocathode was improved and the performance of DSSCs was optimized.The research contents are as follows:?1?Study on slow growth phenomenon of Double SnO₂ DSSCs efficiency.Different sizes of SnO₂ nanocrystals were synthesized by a hydrothermal method,and the DSSCs of four different photoanodes?SnO₂,SnO₂/SL,SnO₂/Al₂O₃,SnO₂/SL/Al₂O₃?were fabricated.The morphology and size of the materials were characterized by XRD,FESEM,TEM and EDS.The photovoltaic properties of the DSSCs were measured under standard conditions?AM 1.5,100mW/cm²?.The charge transfer of DSSCs was studied by electrochemical impedance spectroscopy?EIS?.The results show that the efficiency of DSSCs with scattering layer and Al₂O₃ layer has been significantly improved,especially the photoanode with both layers,the efficiency has reached 2.53%,which is 86%higher than that of pure SnO₂.In addition,the open circuit voltage(V_OC),fill factor?FF?and current density(J_SC)have also been greatly improved.It is found through experiments that the addition of the scattering layer and the Al₂O₃ layer can enhance the dye adsorption capacity of the photoanode.And adding scattering layer can increase the chemical capacitance?C_??of DSSCs,while the photoanode coated with Al₂O₃ can improve the transfer resistance(R_ct)of DSSCs,thereby suppressing the composite reaction of electrons.After long-term tracking test,it was found that the efficiency of SnO₂ DSSCs increased slowly compared with TiO₂ DSSCs.At 20 days,the efficiency of DSSCs reached the highest,up to 4.57%.After that,it had good stability.?2?The influence of the performance of DSSCs with Al doping.SnO₂ nanocrystals with different proportion Al doping were prepared by simple hydrothermal method.Al-doped SnO₂ photoanodes were fabricated by silk-screen printing.XRD,FESEM,TEM,EDS and UV-Vis were used to characterize the morphology and optical properties of the materials.Comparing to pure SnO₂,the open-circuit voltage,short circuit current,fill factor of 2%Al-doped SnO₂ photoanode are 0.6 V,9.61mA/cm²and 61.08%,respectively,in an AM 1.5 solar simulator.The DSSCs energy conversion efficiency of 2%Al-doped SnO₂ improves from 1.28%to 3.51%.Our work demonstrates that the Al-doped SnO₂ nanocrystals for DSSCs can adjust SnO₂conduction band and suppress charge recombination.The energy-conversion efficiency of 2%Al-doped SnO₂ DSSCs effectively is enhanced consequently.?3?Research on DSSCs based on SnO₂/BiVO₄ photoanode.SnO₂ nanocrystals and BiVO₄ nanoparticles were synthesized by hydrothermal method,respectively,and SnO₂/BiVO₄ composites were prepared by mixing in a certain proportion.The materials were characterized by XRD,FESEM and EDS,and the corresponding DSSCs were fabricated.The photovoltaic performance of DSSCs was tested under standard conditions.The results show that BiVO₄ can effectively improve the open-circuit voltage and photoelectric conversion efficiency of DSSCs.Especially when 0.02 g BiVO₄ was added,the performance of DSSCs was the best.The open-circuit voltage can reach 0.55 V,the current density can rise to 10.14mA/cm²,and the efficiency can reach 1.91%,which is 33%higher than that of pure SnO₂.Through the photoanode desorption and EIS test,,it was found that proper amount of BiVO₄ could enhance the ability of SnO₂ to adsorb dyes,inhibit the charge recombination reaction at the interface of DSSCs,and improve the performance of DSSCs.