Electrochemical Preparation And Photoelectric Properties Of Ni₃Se₄/Graphene Composites

Dye-sensitized solar cell?DSSC?is a new type of solar cell,which has the characteristics of low cost,easy fabrication and relatively good photovoltaic performance.In recent years,DSSC has attracted great attention of researchers over the world.Counter electrode?CE?is a key component of DSSC.Excellent CEs need good catalytic activity and high conductivity.The traditional CE material is platinum.However,The reserves of Pt are scarce and the cost is high,and it is easy to be corroded by electrolytes,which limits the industrial production of DSSC.Metal selenide has been proved to be an excellent CE material with excellent catalytic activity and low cost.Graphene is a new two-dimensional material with good electrical conductivity,large specific surface area and catalytic activity.The introduction of graphene is a new direction to improve the performance of CE.Based on the above research background,this paper has done the following research:?1?Ni₃Se₄ films were prepared by a one-step electrochemical deposition method and used directly as DSSC CEs.The study shows that the Ni₃Se₄ prepared are irregular granules with good purity and crystallinity.In addition,the Ni₃Se₄ film prepared by the electrodeposition method has a mirror-like surface.This characteristic can reflect the light that has not been absorbed by the dye back to the photoanode and improve the light-harvesting efficiency,thereby further improving the efficiency of the cell.The effect of deposition time on the performance of Ni₃Se₄ CEs was investigated by electrochemical test and J-V characteristic curve test.The results show that the PCE of DSSC increases with the increase of deposition time,and the performance parameters such as peak current density,R_ct,J₀,J_limim and filling factor are also optimized with the increase of deposition time.However,the SEM shows that the increase of the deposition time will increase the size of the Ni₃Se₄ particles,which will reduce the specific surface area of the film and affect the performance of the electrode.From the results,based on the deposition time of 5min,10min,20min and 40min,the corresponding cell efficiencies were 6.48%,8.19%,8.29%,and 8.34%,respectively.The increase in efficiency after the deposition time reached 10 minutes was very small.Considering the preparation time is also a kind of cost,we choose the deposition time of 10min as the best solution.?2?Graphene oxide was prepared by a modified Hummers method,Ni₃Se₄/Graphene composite films were prepared by electrochemical deposition method,it was used as the DSSC counter electrode for the first time.The research shows that Ni₃Se₄ in composite materials also has good purity and crystallinity,and the graphene oxide is also well reduced.Compared with the Ni₃Se₄ deposited directly on the ITO,the Ni₃Se₄ particles deposited on the surface of the graphene are smaller in size,and the smaller particle size can provide a larger specific surface area for Ni₃Se₄ film,thereby improving the performance of the counter electrode.The test results of cyclic voltammetry,electrochemical impedance and Tafel polarization curves show that the Ni₃Se₄/Graphene composite has the best electrocatalytic performance and conductivity compared with the Ni₃Se₄ and the Pt.Meanwhile,the performance of Ni₃Se₄ is better than that of Pt.This result indicates that,on the one hand,the electrocatalytic activity of Ni₃Se₄ is superior to that of Pt.On the other hand,the introduction of graphene can further improve the performance of the CE.According to the J-V characteristic curve test,the efficiency of DSSCs based on Ni₃Se₄ CE,Ni₃Se₄/Graphene CE,and Pt CE was 8.19%,9.14%,and 8.04%,respectively,which was consistent with the electrochemical test results.In addition,the effect of graphene deposition time on the performance of the CE was also investigated.It was found that when the deposition time was 120 s,the performance of the CE was the best.