Cl掺杂对CuI薄膜发光性能增强研究

Enhanced Band-edge Luminescence of CuI Thin Film by Cl-doping

宽禁带γ-CuI是一种具有优异光电和热电性能的p型透明半导体材料,近年来受到广泛关注。但作为一种新兴材料,其发光性能受材料缺陷影响的物理机理尚不清楚。本工作通过气相反应法制备了Cl掺杂的CuI薄膜,采用电镜表征方法研究Cl掺杂对多晶CuI薄膜表面形貌和阴极荧光发光特性的影响,并结合第一性原理计算探究了Cl在CuI薄膜中的主要存在形式,以揭示Cl掺杂CuI薄膜结构与发光性能的联系。研究结果表明,原本晶粒饱满但晶界显著的CuI薄膜掺杂Cl后呈现出致密平整的表面,表明Cl掺杂剂改变了CuI的表面结构。相比未掺杂区域,Cl掺杂区410nm处的荧光信号明显得到双倍增强,而在720nm附近的缺陷峰则略有降低,说明Cl掺杂极大改善了CuI薄膜的发光性能。通过第一性原理计算对该现象进行理论分析,发现引入Cl元素有效抑制了CuI中碘空位等深能级缺陷的产生,降低了激子发生非辐射跃迁的概率,从而改善CuI的发光性能,这与阴极荧光的结果一致。本研究获得的掺杂CuI薄膜带边发光峰的半峰宽仅为7nm,表现出极高的发光单色性。这些发现有助于对卤素掺杂获得的高性能CuI基材料的理解。

Wide band gapγ-CuI is a p-type transparent semiconductor with excellent optoelectronic and thermoelectric property,which has recently attracted worldwide attention.However,as an emerging material,its luminescence mechanism that is impacted by defects is rarely reported and remains obscure,limiting its further applications.In this work,Cl-doped CuI film was prepared by gas-phase reaction method.Using cathodoluminescence spectroscopy,effects of Cl doping on the surface morphology and cathodoluminescence property of CuI films were investigated in detail,and main defects of Cl presence in CuI films were explored by combining first-principle calculations,revealing relationship between structure and luminescent property of Cl-doped CuI films.These data showed Cl-doped region had a smoother surface than that of the undoped region with granular morphology,which clearly demonstrated that Cl dopant altered surface structure of the undoped region.Compared with the undoped region,the Cl dopant induced doubled fluorescence signal of band-edge emission at 410 nm,but reduced the defect peak at 720 nm,indicating that a small amount of Cl dopant brought a great luminescent improvement to CuI.The formation energy calculations of various crystal defects suggest that Cl can inhibit the formation of deep-level defects such as I vacancy in CuI and reduce the probability of non-radiative transition of excitons,which is consistent with the cathodoluminescence results.The full width at half maximum of the band-edge luminescence peak of Cl-doped CuI film is as small as 7 nm,showing extremely high luminescence monochromaticity.Therefore,the present findings deepen our understanding on how halogen doping boosts the luminescence performance of CuI-based materials.