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采用等离子体化学气相沉积技术,通过交替改变H2流量,制备了多层结构的氢化初始晶硅薄膜,利用拉曼(Raman)散射、傅里叶变换红外(FTIR)透射光谱和光电流谱等技术研究了薄膜的微观结构和光电响应特性.微观结构分析揭示,薄膜呈现为由纳米晶硅和非晶硅两相组成的初始晶硅结构,薄膜光学带隙随晶化度提高逐渐降低.光电流谱的结果显示,纳米硅晶粒对薄膜内部光生载流子的空间分离可有效降低其非辐射复合几率,导致薄膜光电响应峰值随晶化度的提高向短波方向移动,然而纳米硅晶粒界面缺陷对载流子的空间限制使薄膜长波谱段的光电响应显著降低.外加偏压下,观察到350～1000nm范围的光电响应,表明外加偏压可促进光生载流子的有效收集.分析表明,纳米硅晶粒内部电子-空穴对的空间分离及界面载流子激发的共同作用,导致薄膜光电响应及外量子效率大幅增加和峰位的红移.实验结果为初始晶硅高效太阳电池的载流子输运控制提供了基础数据.
The plasma-enhanced chemical vapor deposition (HVDC) technique was used to fabricate a multilayered hydrogenated initial crystalline silicon thin film by alternating H2 flow rate. Raman scattering, Fourier transform infrared (FTIR) spectroscopy and photocurrent spectroscopy The microstructure and the photoelectrical response characteristics of the films were investigated.The microstructure analysis revealed that the films presented an initial crystalline silicon structure consisting of two phases of nanocrystalline silicon and amorphous silicon.The optical bandgap of the films decreased gradually with the increase of crystallinity. The results show that the spatial separation of nano-silicon grains on the photo-generated carriers can effectively reduce the non-radiative recombination probability, which leads to the peak of photoelectric response of the nanostructured silicon film moving toward the short-wave direction with the increase of crystallinity. However, The photoelectrical response of the film in the long-wavelength spectral region was significantly reduced by space constraints on carriers.The photoelectrical response in the range of 350-1000 nm was observed under applied bias voltage, indicating that the external bias could promote the efficient collection of photo-generated carriers.It was shown that, The interaction between electron-hole pairs and interfacial carrier excitation in the nanocrystalline silicon grains leads to a dramatic increase in the photoelectrical response and the external quantum efficiency Red shift results in an initial peak of crystalline silicon solar cells efficient carrier transport control provides basic data.