Photoexcited charge carrier dynamics in Sb2Se3(100)

Abstract

Antimony selenide (Sb2Se3) consists of one-dimensional ribbons that are van der Waals bonded to each other. Due to its favorable optoelectronic properties, it is a promising material for solar energy conversion. Owing to its narrow direct band gap and its high absorption coefficient it is an efficient absorber for solar light. Besides, it is cheap, stable in harsh environments, and abundant with low toxicity. For its use in solar devices, efficient transport of photoexcited charge carriers towards the active interface and long lifetimes at sufficiently high energies are mandatory. Here time-resolved two-photon photoemission experiments on the (100) surface of Sb2Se3 are presented. Data were taken along and perpendicular to the direction of the one-dimensional ribbons in order to unravel the anisotropic lifetimes and relaxation dynamics of photoexcited charge carriers. In both cases, various conduction bands could be populated and within the first picosecond ultrafast scattering towards the lowest conduction band was observed. Moreover, long lifetimes of up to 35 ps in the conduction band bottom at the surface were obtained and no sign of trapping in defect states was found. These measurements shed light on the relaxation and scattering of free carriers in Sb2Se3, which is the key for the design of Sb2Se3-based electrodes.

Ultrafast carrier kinetics at surface and interface of Sb₂Se₃ film by transient reflectance

“…目前关于Sb 2 Se 3 薄膜载流子复合动力学的报 道包含以下几个方面. Yang等 [10] 和Wang等 [11] 分别应用太赫兹泵浦探测技术确定了Sb 2 Se 3 自由 载流子的寿命介于10-30 ps. 同时Wang等 [11] 还 根据Sb 2 Se 3 的纳秒瞬态吸收光谱, 确定其束缚载 流子寿命在10 ns量级.…”

“…Yang等 [10] 和Wang等 [11] 分别应用太赫兹泵浦探测技术确定了Sb 2 Se 3 自由 载流子的寿命介于10-30 ps. 同时Wang等 [11] 还 根据Sb 2 Se 3 的纳秒瞬态吸收光谱, 确定其束缚载 流子寿命在10 ns量级. 根据Sb 2 Se 3 晶体的时间和 角分辨光电子谱测量结果, Grad等 [12] 报道电子由 导带高能级向导带底的弛豫时间约为0.4 ps.…”

“…根据前文分析 可知, 载流子的冷却过程会加强带的填充效应, 引 由负最大值-恢复-转为正值过程持续时间约 为30 ps. Sb 2 Se 3 薄膜的自由载流子寿命约为10-35 ps [11,12] 电子传输层材料 [33,34] .…”

Substrate-Dependent Ultrafast Charge-Carrier Dynamics: Unveiling the Annealing Effect on Optoelectronic Performance of Sb2Se3Thin Films

“…Grad et al. observed a prolonged recombination lifetime of around 35 ps in a two-photon photoemission experiment on a defect-free Sb 2 Se 3 (100) single crystal . Another work, conducted by Wang et al, used THz spectroscopy and transient spectroscopy to investigate carrier trapping and carrier dynamics, discovering a wide PIA signal extending from 800 to 1300 nm and observed hot carrier thermalization time was 0.35 ps, while the trapping time was 23 ps …”

“…Grad et al observed a prolonged recombination lifetime of around 35 ps in a two-photon photoemission experiment on a defect-free Sb 2 Se 3 (100) single crystal. 27 trapping and carrier dynamics, discovering a wide PIA signal extending from 800 to 1300 nm and observed hot carrier thermalization time was 0.35 ps, while the trapping time was 23 ps. 28 Palwinder Singh et al reported low-temperature and roomtemperature transient spectra for the amorphous and crystalline films.…”