Kavanagh Seán R, Scanlon David O, Walsh Aron, Freysoldt Christoph
Department of Chemistry & Thomas Young Centre, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
Department of Materials & Thomas Young Centre, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
Faraday Discuss. 2022 Oct 28;239(0):339-356. doi: 10.1039/d2fd00043a.
The efficiency of a solar cell is often limited by electron-hole recombination mediated by defect states within the band gap of the photovoltaic (PV) semiconductor. The Shockley-Read-Hall (SRH) model considers a static trap that can successively capture electrons and holes. In reality however, true trap levels vary with both the defect charge state and local structure. Here we consider the role of metastable structural configurations in capturing electrons and holes, taking the tellurium interstitial in CdTe as an illustrative example. Consideration of the defect dynamics, and symmetry-breaking, changes the qualitative behaviour and activates new pathways for carrier capture. Our results reveal the potential importance of metastable defect structures in non-radiative recombination, in particular for semiconductors with anharmonic/ionic-covalent bonding, multinary compositions, low crystal symmetries or highly-mobile defects.
太阳能电池的效率通常受到光伏（PV）半导体带隙内缺陷态介导的电子-空穴复合的限制。肖克利-里德-霍尔（SRH）模型考虑了一个能够相继捕获电子和空穴的静态陷阱。然而在实际中，真正的陷阱能级会随缺陷电荷状态和局部结构而变化。在此，我们以碲化镉中的碲间隙原子为例，考虑亚稳结构构型在捕获电子和空穴方面的作用。对缺陷动力学和对称性破缺的考虑改变了定性行为，并开启了新的载流子捕获途径。我们的结果揭示了亚稳缺陷结构在非辐射复合中的潜在重要性，特别是对于具有非谐/离子-共价键、多元成分、低晶体对称性或高迁移率缺陷的半导体而言。
