| In recent years, with the rise of two-dimensional materials research, transition metal sulfide semiconductor material which has two-dimensional layered structure has aroused concern. Molybdenum disulfide（Mo S2） is a typical layered transition metal chalcogenides.Its structure is very similar to the layered structure of graphene. Dimensional Mo S2 has excellent electrical, optical and semiconductor properties. Together with adjustable bandgap, molybdenum disulfide has great prospects in the semiconductor optoelectronic devices.Chemical vapor deposition（CVD） process for the preparation method is simple and can achieve a large area continuous and mass synthesis of film, ease of forming doped films to fabricate heterojunction photovoltaic device, and it is is also applicable to grow other TMDCs material, having great prospects for industrial application. The advantage of CVD is that it allows of the preparation of high purity, crystallinity dimensional Mo S2 nano film.It has a value in the manufacture of monocrystalline and polycrystalline product which require high lattice arrangement. It is the most effective method for preparing large area,high quality Mo S2 film, having advantage in the thickness,size and the control of physical properties. In this artical, the Mo S2 nano film was deposited directly on quartz substrate by CVD approach using Mo O3 and sulfur powders as reactants. The surface morphology of the grown films was observed by metallographic optical microscope, scanning electron microscope（SEM） and atomic force microscopy（AFM）. Raman spectroscopic and photoluminescence（PL） spectroscopic analyses were conducted to evaluate the structural and optical property of the grown Mo S2 nano films. Monolayer Mo S2 film with thickness of 0.9nm was found by AFM. Thin films were characterized by Raman spectra, the Raman spectra of grown Mo S2 nano film has two characteristic peaks, corresponding to E2g1 and A1 g. There are Raman shifts with 19cm-1, 21.5cm-1, 23cm-1and 25cm-1, corresponding tosingle, double, triple and bulk MoS2 films, respectively. So we can make a preliminary determination that single, double, triple and bulk Mo S2 films have been grown on a quartz substrate. Meanwhile photoluminescence spectrum was conducted to analyze the optical properties of grown film, which further defined the single, double and triple layer Mo S2 films. Photoluminescence phenomenon were observed in single, double and triple layer Mo S2 films, the PL spectrum peaks of monolayer Mo S2 are at 670.7nm（1.85eV） and620nm（2eV）. The difference between the shoulder peak and the main peak is 0.15 eV, this is due to the 150 me V spin split of valence band resulting from spin coupling effect in monolayer Mo S2. In single, double and triple layer Mo S2 films, PL peak positions have a red shift, which indicates that with the reduction of Mo S2 film layers, optical band gap of Mo S2 becomes larger. The optical properties of two-dimensional Mo S2 films were studied.When MoS2 film turning from bulk to monolayer, the change of the band structure was analyzed theoretically, which is consistent with the experimental results. Finally, we use CVD to vulcanize Mo O3 film grown on the p-Si substrate to grow Mo S2 film. The p-Si and the Mo S2 film form a heterojunction. Basing on this, solar cell was fabricated. The test results of the solar cell show that there are photovoltaic effect in Mo S2 / p-Si heterojunction, and the open circuit voltage, short circuit current density, fill factor,conversion efficiency are 0.17 V, 0.324mA/cm2, 0.213, 0.012%, respectively. Further experiment is needed to improve the quality of the Mo S2 film. Our work shows that Mo S2/ p-Si heterojunction solar cell has great potential in solar cell applications. |
