シリコン系ナノ結晶表面での多重励起子の生成

采用液体介质激光烧蚀技术，在非晶ssi靶材表面产生高定域等离子体，制备了ssi -ncs。该方法合成了ssi -ncs合金，这是使用薄膜沉积、高频等离子体增强化学气相沉积或脉冲激光沉积等传统技术无法实现的。所制备的纳米颗粒达到约4nm的量子约束尺寸，通过透射电子显微镜观察到其原子结构清晰。采用同步辐射XRD分析了si0.88 - sn0.12 -ncs合金，得到了理论上符合直接能隙跃迁的si0.88 - sn0.12 -ncs合金。光带隙通过吸光度测量估计为0.81eV，远低于硅带隙。傅里叶瞬态红外光谱显示ssi -ncs表面存在低浓度的氧，这对器件的稳定性具有重要意义。利用混合太阳能电池器件分析了ssi -ncs的光伏性能。我们的研究结果强调了使用共轭聚合物PTB7与sis -ncs混合作为有源层的器件的短路电流的改善。这种改进与较长波长的更好的吸收有关，这是由于低能量带隙和它可能的直接跃迁。开路电压的改善也被证实，这与体异质结质量有关。这是第一次报道ssi -ncs合金的光伏效应。

SiSn-ncs were fabricated by laser ablation in liquid media technique that generates high localized plasma on the surface of amorphous SiSn target. This method synthetized SiSn-ncs alloys that was not possible using conventional techniques such as thin film deposition, high frequency plasma enhanced chemical vapor deposition, or pulsed laser deposition. The nanoparticles generated reach a quantum confinement size about 4nm with clear atomic plans observed by transmission electron microscopy. SiSn-ncs were analyzed by synchrotron radiation XRD to estimate a Si0.88Sn0.12-ncs alloys that can correspond theoretically to direct energy gap transition. Optical bandgap was estimated to be 0.81eV by absorbance measurements, which is well below the silicon bandgap. A low concentration of oxygen on the surface of SiSn-ncs was underlined by Fourier transient infrared spectra, which is of great importance for the stability over time of the devices.The photovoltaic properties of SiSn-ncs were also analyzed using hybrid solar cell devices. Our findings underlines an improvement of the short-circuit current for devices using conjugated polymer PTB7 mixed with SiSn-ncs as active layer. This improvement is related to a better absorption at longer wavelengths due to the low energy band gap and also due to its possible direct transition. An improvement of the open-circuit voltage is also confirmed, related to the bulk heterojunction quality. It is the first report about the photovoltaic effect of SiSn-ncs alloy.