Tiwari Devendra, Yakushev Michael V, Koehler Tristan, Cattelan Mattia, Fox Neil, Martin Robert W, Klenk Reiner, Férmin David J
Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Ellison Place, NE1 8ST Newcastle upon Tyne, United Kingdom.
School of Chemistry, University of Bristol, Cantocks Close, BS8 1TS Bristol, United Kingdom.
ACS Appl Energy Mater. 2022 Apr 25;5(4):3933-3940. doi: 10.1021/acsaem.1c03729. Epub 2022 Mar 22.
The sub-bandgap levels associated with defect states in CuZnSnS (CZTS) thin films are investigated by correlating the temperature dependence of the absorber photoluminescence (PL) with the device admittance spectroscopy. CZTS thin films are prepared by thermolysis of molecular precursors incorporating chloride salts of the cations and thiourea. Na and Sb are introduced as dopants in the precursor layers to assess their impact on Cu/Zn and Sn site disorder, respectively. Systematic analysis of PL spectra as a function of excitation power and temperature show that radiative recombination is dominated by quasi-donor-acceptor pairs (QDAP) with a maximum between 1.03 and 1.18 eV. It is noteworthy that Sb doping leads to a transition from localized to delocalized QDAP. The activation energies obtained associated with QDAP emission closely correlate with the activation energies of the admittance responses in a temperature range between 150 K and room temperature in films with or without added dopants. Admittance data of CZTS films with no added dopants also have a strong contribution from a deeper state associated with Sn disorder. The ensemble of PL and admittance data, in addition to energy-filtered photoemission of electron microscopy (EF-PEEM), shows a detailed picture of the distribution of sub-bandgap states in CZTS and the impact of doping on their energetics and device performance.
通过将吸收体光致发光（PL）的温度依赖性与器件导纳谱相关联，研究了CuZnSnS（CZTS）薄膜中与缺陷态相关的子带隙能级。CZTS薄膜通过热解包含阳离子氯化物盐和硫脲的分子前驱体制备。将Na和Sb作为掺杂剂引入前驱体层，分别评估它们对Cu/Zn和Sn位点无序的影响。作为激发功率和温度函数的PL光谱的系统分析表明，辐射复合主要由准施主-受主对（QDAP）主导，其最大值在1.03至1.18 eV之间。值得注意的是，Sb掺杂导致从局域化QDAP向离域化QDAP的转变。在添加或未添加掺杂剂的薄膜中，与QDAP发射相关的活化能在150 K至室温的温度范围内与导纳响应的活化能密切相关。未添加掺杂剂的CZTS薄膜的导纳数据也有来自与Sn无序相关的更深能级的强烈贡献。PL和导纳数据的集合，除了电子显微镜的能量过滤光发射（EF-PEEM）外，还展示了CZTS中子带隙态分布的详细情况以及掺杂对其能量和器件性能的影响。
