Chen Zhi, Zhang Ping-Zhi, Zhou Yu, Zhang Xingming, Liu Xiaorui, Hou Zhufeng, Tang Jianfeng, Li Wei
School of Chemistry and Materials Science, Hunan Agricultural University, Changsha 410128, People's Republic of China.
School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, People's Republic of China.
J Phys Chem Lett. 2020 Dec 17;11(24):10354-10361. doi: 10.1021/acs.jpclett.0c03175. Epub 2020 Nov 24.
We report a time-domain simulation of charge carrier trapping and relaxation dynamics in pristine and defect-containing kesterite CuZnSnS (CZTS) structures. Our simulations show that introduction of a neutral sulfur vacancy in the CZTS system leads to a decrease of the charge recombination rate by a factor of ∼4, and the doubly positively charged sulfur vacancy results in a minor decrease of carrier lifetime, as compared to the pristine CZTS system. The neutral sulfur vacancy weakens the nonadiabatic (NA) electron-phonon coupling by moderately localizing charge density and accelerates the pure dephasing process, extending charge carrier lifetime. Therefore, the neutral sulfur vacancy is electrically benign. The doubly positively charged sulfur vacancy introduces a subgap state which is hardly populated, and recombination of the electron and hole bypassing the trap state dominates. As a result, the recombination rate decreases in the doubly charged sulfur vacancy structure. The reported results identified the key role of the sulfur-related vacancy on charge carrier trapping and relaxation of CZTS materials, carrying important implications for further optimization of CZTS and other thin-film solar cell materials.
我们报告了在原始的和含有缺陷的锡锌黄铁矿CuZnSnS（CZTS）结构中电荷载流子俘获和弛豫动力学的时域模拟。我们的模拟表明，在CZTS系统中引入中性硫空位会导致电荷复合率降低约4倍，与原始的CZTS系统相比，双正电荷硫空位会导致载流子寿命略有下降。中性硫空位通过适度地局域电荷密度来减弱非绝热（NA）电子-声子耦合，并加速纯退相过程，从而延长电荷载流子寿命。因此，中性硫空位在电学上是无害的。双正电荷硫空位引入了一个几乎不被占据的亚带隙态，电子和空穴绕过陷阱态的复合占主导。结果，双电荷硫空位结构中的复合率降低。所报道的结果确定了硫相关空位对CZTS材料中电荷载流子俘获和弛豫的关键作用，对进一步优化CZTS和其他薄膜太阳能电池材料具有重要意义。
