退火温度对TiO2/CdSe纳米片异质结薄膜光电性能的影响

摘要

采用水热法在FTO上制备(001)高活性晶面主导的TiO2纳米片薄膜,利用循环伏安法在TiO2纳米片薄膜上沉积CdSe颗粒,制备了TiO2/CdSe纳米片异质结薄膜.分别在150、250、350、450℃,氩气保护气氛中对样品进行退火.利用X射线衍射仪(XRD)、场发射扫描电镜(FESEM)、X射线光电子能谱分析仪(XPS)、紫外-可见(UV-Vis)分光光度计以及电化学工作站对不同温度退火后的TiO2/CdSe纳米片异质结薄膜的微观形貌、晶体结构、光电化学性能进行表征和测试.结果表明:六方相CdSe纳米颗粒均匀包覆在TiO2纳米片表面,直径30 nm左右;随着退火温度的升高CdSe纳米颗粒长大,形成光滑的CdSe薄膜,且晶化程度提高;TiO2纳米片表面的Se元素与Cd元素发生氧化;TiO2/CdSe纳米片异质结薄膜对可见光的吸收光谱发生红移,禁带宽度逐渐减小.光电化学性能测试表明随着退火温度的升高,TiO2/CdSe纳米片异质结薄膜的光电流密度显著提高,开路电压减小,但由于SeO2和CdO的出现,导致填充因子减小,影响光电转换效率的提高.在本实验条件下,TiO2/CdSe纳米片异质结薄膜的最佳退火温度为150℃,填充因子为0.77,光电转换效率达到3.12％.%TiO2 nanosheeet thin films were prepared by hydrothermal method.TiO2/CdSe nanosheet heterojunction thin films were prepared by electrochemical depositing CdSe nano-particles on the TiO2 nanosheets with (001) facets dominated.The synthesized films were annealed at 150,250,350 and 450 C under the protection of Ar gas.The effect of annealing on TiO2/CdSe nanosheet heterojunction thin films was studied by X-ray diffraction(XRD),field emission scanning eletron microscopy(FESEM),X-ray photoelectron spectroscopy(XPS),UV-Vis diffuse reflection spectrum (UV-Vis) and electrochemical workstation.The result indicates that hexagonal phase CdSe nanoparticles distribute on the surface of TiO2 nanosheet films uniformly with a diameter of 30 nm.With the increase of annealing temperature,CdSe nanoparticles are agglomerated and grown;the degree of crystallization increases;the Se and Cd on the surface of TiO2 nanosheets are oxidized;the absorption spectra appears red shift and the band gap reduces.The photoelectric performance test shows that the photocurrent density of the TiO2/CdSe nanosheet heterojunction thin films increases with the increase of the annealing temperature,but the open circuit voltage and the filling factor decreases,which leads to a reduction in the efficiency of photoelectric conversion.In this experimental condition,the optimum annealing temperature of TiO2/CdSe nanosheet heterojunction films is 150 ℃.The filling factor is 0.77 and the photoelectric conversion efficiency reaches 3.12％.