Charge carrier dynamics and self-trapping onSb2S3(100),Physical Review Materials

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Charge carrier dynamics and self-trapping onSb2S3(100)
Physical Review Materials ( IF 3.1 ) Pub Date : 2021-07-08 , DOI: 10.1103/physrevmaterials.5.075401
Lisa Grad ₁ , Fabian O. von Rohr ₂ , Matthias Hengsberger ₁ , Jürg Osterwalder ₁

Affiliation

Antimony sulfide (

{Sb}_{2} S_{3}

) is a promising material for solar energy conversion. It consists of earth-abundant elements with a low toxicity and high stability. Furthermore, it shows suitable optical and electronic properties like a large absorption coefficient and a convenient band gap of 1.7 eV. Nevertheless, so far, the obtained power conversion efficiencies and the open circuit voltages are far below the theoretical limits and need to be increased for a viable application of

{Sb}_{2} S_{3}

-based cells at the large scale. To achieve this it is important to identify the dominating loss mechanism. Here time-resolved two-photon photoemission experiments are presented from the (100) surface of a cleaved

{Sb}_{2} S_{3}

single-crystal to investigate the charge carrier dynamics after photoexcitation. Based on these measurements an ultrafast relaxation within below 150 fs towards the conduction band minimum is observed. This is followed by a decay within 1 ps into states, which are located in the band gap 0.06 eV and 0.44 eV below the conduction band minimum where the charge carriers have long lifetimes of 27 ps and 63 ps, respectively. Based on the energetic position, the energy width and the formation time of the lower-lying gap state a self-trapping mechanism of free charge carriers by optical phonons with a frequency of 1.44 THz is proposed, and the results are discussed in this context. These findings provide evidence that the poor performance of

{Sb}_{2} S_{3}

in solar devices can be traced back to intrinsically formed traps that can hardly be avoided.

中文翻译：

Sb2S3(100) 上的电荷载流子动力学和自陷

硫化锑（

锑_{2} 秒_{3}

) 是一种很有前途的太阳能转换材料。它由地球上丰富的元素组成，具有低毒性和高稳定性。此外，它显示出合适的光学和电子特性，如大吸收系数和 1.7 eV 的方便带隙。然而，到目前为止，获得的功率转换效率和开路电压远低于理论极限，需要增加才能实现

锑_{2} 秒_{3}

- 大规模的基于细胞。为了实现这一点，确定主要的损失机制很重要。这里时间分辨的双光子光电发射实验是从解理的 (100) 表面呈现的

锑_{2} 秒_{3}

单晶研究光激发后的电荷载流子动力学。基于这些测量，观察到在 150 fs 以下朝向导带最小值的超快弛豫。随后在 1 ps 内衰减到位于导带最小值以下 0.06 eV 和 0.44 eV 的带隙中，其中电荷载流子的寿命分别为 27 ps 和 63 ps。基于低能隙态的能量位置、能量宽度和形成时间，提出了频率为 1.44 THz 的光声子对自由电荷载流子的自陷机制，并在此背景下讨论了结果。这些发现提供了证据表明

锑_{2} 秒_{3}

在太阳能设备中，可以追溯到难以避免的本质上形成的陷阱。

更新日期：2021-07-08

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