Preparation Of ZnO/graphene Composite Films By One-step Electrodeposition And Their Photoelectric Properties

In recent years,zinc oxide(ZnO),as an n-type semiconductor material,has the advantages of wide band gap(about 3.37 e V),high exciton binding energy(60 me V),excellent electrochemical stability,good electron mobility,diversified preparation methods,rich morphology and structure and perfect optical transmittance in the visible wavelength range have become one of the most promising materials for optoelectronic applications can use in optoelectronics field.However,ZnO has the problems of low absorption of the visible part of the solar spectrum and high carrier recombination rate generated by photons,which hinders the further improvement of the performance of ZnO based devices.In order to overcome these shortcomings,the composites of ZnO and graphene have been widely studied by many scholars.At present,ZnO and graphene composite materials are prepared by solvothermal treatment,chemical vapor deposition,ultrasonic spray pyrolysis and other harsh conditions involving complex operation,high temperature and high pressure.In order to solve the above problems,ZnO-rGO composite films were synthesized by one-step electrodeposition method with simple operation,low cost and no high temperature and high pressure.By introducing reduced graphene oxide(rGO)into ZnO,ZnO-rGO composites with increased specific surface area,reduced photogenerated electron hole pair recombination and increased conductivity were prepared,so that their photoelectric properties were improved compared with ZnO.The main research contents of this paper are as follows:(1)ZnO nanorods with uniform orientation and small diameter were prepared by one-step electrodeposition method by changing electrochemical parameters to control the nucleation and growth rate of ZnO nanorods.rGO films were prepared by electrodeposition,which shows that the preparation of ZnO-rGO composite films by electrodeposition is feasible.Through the characterization of X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and energy dispersive X-ray diffraction(EDS),the optimal parameters for the one-step preparation of ZnO-rGO composite films by electrodeposition are determined as follows:GO concentration in precursor solution is 5 mg L^-1,deposition potential is-1.1 V and deposition time is 600 s.(2)ZnO-rGO composites with good light absorption capacity and more surface-active sites were synthesized by adjusting the concentration of GO added to the electrolyte,deposition potential and time.ZnO-rGO composite was used as catalyst in the field of photocatalysis.The photocatalytic performance of ZnO-rGO as catalyst was evaluated through the experiment of photocatalytic degradation of different organic dyes.The ZnO-rGO catalyst prepared with 5 mg L^-1 GO electrolyte can degrade 99.1%MB in 120 min.(3)ZnO-rGO photoanode is prepared to solve the problems of low charge transfer rate,high carrier recombination rate generated by photons and low absorption and utilization rate of visible light part of solar spectrum when ZnO is used as photoanode.The optimum parameters were determined as follows:GO concentration in precursor solution was 5 mg L^-1,deposition potential and time were-1.1 V and 600 s.The band gap and charge transfer kinetics were analyzed by ultraviolet visible spectroscopy(UV-vis),electrochemical impedance spectroscopy(EIS)and incident photoelectron conversion spectroscopy(IPCE).It was proved that the addition of rGO could effectively increase the conductivity and reduce the recombination of photogenerated electron hole pairs.The photoelectric conversion efficiency(PCE),open circuit voltage(V_OC),short-circuit current density(J_SC)and filling factor(FF)of ZnO-rGO photoanode were 1.07%,386.15 m V,4.65 m A cm^-2 and 0.59,respectively.(4)Through SEM,J-V curve and stability test,it is proved that adding rGO to ZnO based electron transport layer to prepare ZnO-rGO electron transport layer can effectively reduce the number of hydroxyl groups on ZnO surface,avoid the direct contact between hydroxyl groups and CH₃NH₃Pb I₃ layer,and play the role of surface passivation.The photoelectric conversion efficiency(PCE),open circuit voltage(V_OC),short circuit current density(J_SC)and filling factor(FF)of PSC device based on ZnO-rGO electron transport layer are 11.03%,821.74 m V,22.59 m A cm^-2 and 0.59.The efficiency remains at the initial98%after 60 hours of storage in air.