| In the process of the development and utilization of new energy, photovoltaicsolar cell application has became one of the fastest-growing and the most influentialfield in scientific research. In the same time, the preparation of semiconductormaterial for solar cell became a hot research topic. A lot of semiconductor materialswith the nature of the P-type or N-type received wide attention for scientists. Whenthe different properties of the semiconductor material grow together, they can beformed P-N junction barrier in their interface, and prompting photoinducedelectron-hole pairs are effectively separated. Therefore, the composite of the P-typesemiconductor material and the N-type semiconductor material has been extensivelystudied in recent years.Cadmium Selenite (CdSe) is an N-type semiconductor material with band gap of1.76eV at room temperature, which is a direct transition band structure. It caneffectively absorb the energy of visible light, so there are broad prospects inphotovoltaic devices. Cadmium telluride (CdTe) is a P-type semiconductor materialwith bandgap of1.45eV at the room temperature, which is an indirect transition typeband structure and well matched with the solar spectrum. Therefore, it is a goodphotovoltaic material with high theoretical conversion efficiency (28%) inphotovoltaic energy conversion. At the same time, its performance is very stable, which is a popular thin-film solar cells in technically development. Study from theexperimental results, Cadmium telluride is easily to form into a large area of thinfilms, and the deposition rate is high. It is advantageous for improving itsphotoelectric properties if can obtained the CdSe/CdTe thin heterojunction. However,there are few reports on the preparation and photoelectric performance of thenanorods array CdSe/CdTe thin film heterojunction. In this paper, CdSe microrodsarray films are prepared on the ITO substrate, while the growth of CdTe thin film ontheir surface, at the same time, their photoelectric properties have been studied. Themain work is as follows:（1）It is reported here that the microrods array of CdSe on indium doped tin oxidecoated conducting glass (ITO) substrate has been developed by a simpleelectrochemical synthesis method. The electrodeposition of CdSe was alsoinvestigated by cyclic voltammetry technique. Field emission scanning electronmicroscope (FESEM) results show that the microrods’ length, diameter, and directionof growth are nearly uniform and perpendicular to the ITO substrate.Photoelectrochemical solar cells are constructed using CdSe microrods array as thePhotoanode in polysulphide electrolyte and their power output characteristics arestudied, which are0.398V (open circuit voltage),1.57mA/cm2(short circuit current)and0.256%(photoelectric conversion efficiency), respectively.（2）Wheat-like CdSe nanorods array films were prepared on the ITO substrate inthe solution with a low concentration of sulfuric acid. SEM images show that a morewheat-like CdSe array can be prepared in electrolyte solution containing0.01MCdSO4,0.01M Na2SeO3and0.208M H2SO4. A possible growth mechanism of thewheat-like CdSe array was proposed by analyzing the morphology of differentreaction stages. Photoelectrochemical properties of the wheat-like CdSe nanorodsarray films prepared using different concentration of sulfuric acid electrolyte solution were discussed. The photoelectrochemical measurement results showed that thewheat-like the array film having better photoresponse characteristics than the CdSenanorods array film. the samples’ the open circuit voltage, short circuit current densityand photoelectric conversion efficiency can reach up to1.08V,4.06mA/cm2and1.15%, respectively. Compared to the photoelectrochemical properties of the CdSenanorods array thin film, the reason that the wheat-like CdSe array film has a muchlarger surface area than the CdSe nanorods array thin film, which can increase theintensity of the light scattering for enhancing light capture, and increasing the contactarea with the test electrolyte. Therefore, these results are beneficial to thephotoelectrochemical properties of the wheat-like of CdSe array thin films.（3）CdTe films with sphalerite structure were prepared on the wheat-like CdSenanorods array film surface using the close-spaced sublimation method, the thicknesswas about10μm. It can be seen from the SEM images, CdTe films grew on thewheat-like CdSe array thin film surface. A significant red-shift of the absorption edgeis observed owning to the composite of CdTe and CdSe. The p-n heterojunction isformed at the interfaces of n-type wheat-like CdSe nanorods and p-type CdTe thinfilm owning to the nonlinear I-V curve. Therefore, we have successfully prepared theCdSe/CdTe thin film heterojunction solar cells, the open circuit voltage is0.274V, theshort circuit current density is8.34mA/cm2, and photoelectric conversion efficiencywas0.557%. The results of the battery in the solar spectrum incident quantumconversion efficiency (IPCE) show that the photoelectric conversion efficiency canreach up to17.2%at786nm. Furthermore, the photoelectric conversion mechanism ofthe CdSe/CdTe thin film heterojunction solar cells was also discussed. |
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