摘要/Abstract

硼烯基纳米复合体是一种极具潜力的电极材料，因此硼烯的功函调控对于最大化器件的能量转换效率及性能至关重要.本工作基于第一性原理密度泛函理论，研究了Li吸附对双层α-硼烯（DBBP）的结构、电子性质和功函的影响及影响Li_n/DBBP功函变化的因素（如基底变形、电子转移、真空和费米能级）.结果表明，Li吸附可将DBBP的功函从4.65 eV调低至1.96～4.46 eV，优于文献报道的Li吸附单层BBP （从4.16 eV调至2.31～3.67 eV）、双层石墨烯中插入Li （3.4～3.9 eV）和K （3.3～3.8 eV）的功函调控效果.其中，Li_2（D）/DBBP （3.73 eV）和Li_3（D）/DBBP的功函（2.91 eV）分别与常用的电极材料Mg （3.68 eV）和Ca （2.90 eV）相近，Li_4（D）/DBBP的功函（1.96 eV）甚至低于Ca.本研究表明Li吸附是降低DBBP功函的一种简单而有效的方法，具有金属性和低功函的Li吸附DBBP纳米材料在电子器件中的阴极材料方面具有应用价值.
关键词: 硼烯, 功函, 吸附, 电子结构, 结合能
As a new member of the two-dimensional nanomaterial family, borophene is regarded as a potential material platform for nanoscale electronic devices. Especially, borophene-based electrodes have potential application values in light-emitting diodes, organic light-emitting diodes, organic solar cells and field emitters. Therefore, the work function modulation (to an optimal value) of borophene is highly important to maximize the energy conversion efficiency and performance of the device. Based on the first-principles density functional theory, the effects of Li adsorption on the structure, electronic properties and work function of double-layer α-borophene (DBBP) are studied. The calculation results show that Li adsorption can effectively adjust the work function of DBBP from 4.65 eV to 1.96~4.46 eV with different Li contents. This engineering range is superior to what are reported in the literatures for Li-adsorbed monolayer BBP (modified from 4.16 eV to 2.31~3.67 eV), and double-layer graphene with intercalated Li (3.4~3.9 eV) and K (3.3~3.8 eV). The work functions of Li_2(D)/DBBP (3.73 eV) and Li_3(D)/DBBP (2.91 eV) are close to the commonly used electrode materials Mg and Ca, respectively, while the work function of Li_4(D)/DBBP is even lower than Ca. In addition, the factors that affect the work function reduction of Li_n/DBBP relative to DBBP, such as configuration, substrate deformation, binding energy, electron transfer, charge rearrangement, electrostatic potential, vacuum and Fermi level, are systematically studied. The results demonstrate that the decrease in the Li_n/DBBP work function is mainly due to the change in Fermi level, while the change in vacuum level only plays a minor role. Apart from that, the deformation of the substrate does not have a positive effect on the reduction of the Li_n/DBBP work function, but the electron transfer from the adsorbed atoms to the matrix (charge redistribution caused by chemical effects) is the inherent reason for the decrease in the Li_n/DBBP work function. This study shows that Li adsorption is a simple and effective method to reduce the work function of DBBP. Due to its metallic character and extremely low work function, Li-adsorbed DBBP nanomaterials can be utilized as cathode materials in electronic devices.
Key words: borophene, work function, adsorption, electronic structure, binding energy


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