Study On Performance Of Dye-sensitized Solar Cells Based On Nitrogen-doped Carbon Counter Electrode

Dye-sensitized solar cells(DSSCs)have attracted many researchers due to low cost?simpleness of preparation?high energy conversion efficiency and environmental friendliness.As one of the most important components of dye sensitized solar cells,the counter electrode(CE)is utilized to transfer electrons from the external circuit back to the redox electrolyte,catalyze the reduction of triiodide(I3-)to iodide(I-)and reflect the transmitted sunlight.Pt has been conventionally used as the ideal CE due to its high catalytic activity and excellent conductivity,however,Pt is a scarce and costly resource,which greatly limits the popularization and application of dye-sensitized solar cell in real life.Therefore,it is urgent to explore a kind of cheap and efficient counter electrode material to replace the traditional Pt counter electrode.This dissertation is mainly concentrated on using carbon materials as the carrier of the counter electrode,modifying them via nitrogen doping or pore forming.And then the effects of carbon counter electrode materials on the photoelectric performance of dye-sensitized solar cells,and the reason for the enhanced electrocatalytic performance of carbon counter electrode materials were studied.The main research results are as follows:(1)Bagasse and urea were used as carbon precursor and nitrogen sources,respectively,nitrogen doped bagasse-derived carbon(NBC)was synthesized by a simple and environmental hydrothermal method,and then chemical reduction method was used to reduce the H2PtCl6 to Pt,which the low Pt was loaded on the carrier of NBC,finally,we successfully prepared the nitrogen-doped bagasse-derived carbon/low Pt(NBC/Pt).Compared with the traditional Pt CE,the NBC/Pt CE had stronger reflection sunlight,accelerated the catalytic reduction reaction of I3-,and reduced the transmission resistance of the electrolyte/CE,thereby shortened the electron transmission life of the NBC/Pt/electrolyte interface,and greatly enhanced the electrocatalytic activity of NBC/Pt CE.Moreover,the current density(Jsc),open circuit voltage(Voc)and fill factor(FF)of the NBC/Pt DSSCs were improved,its photoelectric conversion efficiency(?)was improved from 6.09%to 6.98%.(2)Graphene oxide(GO)was prepared by the modified Hummers' method,and the nitrogen doped porous graphene(N-prGO)was synthesized by hydrothermal method and high temperature calcination method.The experimental results showed that the nitrogen doping and porous structure can effectively increase the specific surface area of N-prGO and provide more catalytic active sites,thus greatly improving the electrocatalytic activity.The electrochemical characterizations of electrochemical impedance spectroscopy(EIS),cyclic voltammetry(CV)and Tafel curves suggested that N-prGO had the minimum transmission resistance of counter electrode/electrolyte interface and the optimal electrocatalytic performance.The J-V curves showed that the photoelectric properties of N-prGO DSSCs compared with Pt DSSCs had been improved.The photocurrent density and photoelectric conversion efficiency were reached to 13.9 mA cm-2 and 6.52%,respectively,which was increased by 9.45%and 11.1%respectively compared with the traditional Pt DSSCs.