Study On The Synthesis Of Graphene Based Nanomaterial And Its Application On Photovaltaics

To solve the energy crisis and environmental pollution problems,researchers have been prompted to intensively investigate solar cells which can provide clean and renewable energy to reduce the consumption of fossil fuels.Dye-sensitized solar cells(DSSCs)and perovskite solar cells are promising photovoltaic devices,primarily because of their sample process,low cost and high efficiency.Inspired by the fact that the hybrid materials can provide superior electrochemical performance due to the positive synergistic effect,we describe a novel graphene based hybrid material that exhibits both high conductivity and excellent catalytic activity to substitute for precious metals platinum(Pt)in DSSC.In addition,we have used the self-doped graphene as the hole transport material for high stability and performance perovskite solar cells.The research contents in this thesis are as follows:(1)We report,for the first time,the synthesis of a hybrid catalyst composed of fullerene-structured MoSe2 hollow spheres anchored on highly nitrogen-doped graphene(referred to herein as HNG)to simultaneously optimize conductivity and catalytic activity.Since the conductivity and catalytic activity of the composites depended on the degree of N-doping in the graphene as well as the MoSe2 structure,we highlight the importance of incorporating the small molecule diethylenetriamine(DETA)to provide a high N content for doping graphene and to serve as a surfactant for fullerene-structured MoSe2 hollow spheres.More importantly,our HNG-MoSe2 hybrid catalyst exhibits excellent catalytic activity and conductivity comparable to that of Pt due to the superior synergy between HNG and MoSe2.The resulting DSSC shows a conversion efficiency of 10.01%,which is close to that observed for Pt-based DSSC(10.55%).(2)We describe a novel quasi core-shell hybrid material that exhibits both high conductivity and excellent catalytic activity.The material consists of a core of CoS nanoparticles coated with a shell of ultrathin N-doped graphene(NDG)layers that act as conductive paths to overcome the problem of low conductivity due to grain boundaries and defects between the CoS nanoparticles.A DSSC prepared with this quasi core-shell NDG/CoS catalyst as the CE showed a high short-circuit current density(20.38 mA cm-2)and an energy-conversion efficiency of 10.71%,which is,as far as we know,the highest reported efficiency for a DSSC based on a Pt-free CE.(3)We demonstrated a hybrid catalyst composed of reduced graphene oxide/Cu2S quantum dots as a transparent CE for DSSC.Owing to the synergistic effect between ultrathin-RGO and ultrasmall-QDs,the counter electrode based on the hybrid catalyst displayed highly transparent performance,excellent conductivity,and catalytic activity.Meanwhile,with regard to above advantages,the DSSC based on this hybrid catalyst achieved the efficiency of 7.12%,which is comparable to that of Pt device(7.38%).(4)We introduce the high conductive reduced graphene oxide(RGO)into graphene oxide to enhanced graphene conductivity of GO for the first time.We used the self-assembly method to prepared the GO-RGO film and the UV-O3 treatment for higher level work function of GO-RGO.Afterwards,the perovskite solar cell obtained the PCE of 14.11%and high stability based on the stable GO-RGO hole transport material.