The efficiencies of ${\mathrm{Cu}}_2\mathrm{ZnSn}{\mathrm{Se}}_4$ (CZTSe) solar cells with a narrower band gap at 1.0 eV are currently higher than those of ${\mathrm{Cu}}_2\mathrm{ZnSn}{\mathrm{S}}_4$ (CZTS), with the optimal band gap according to the Shockley-Queisser model. To understand this abnormal observation, we studied the nonradiative recombination rates induced by the deep levels of the dominant defects in CZTSe, i.e., the ${\mathrm{Sn}}_{\mathrm{Zn}}\left(2+/+\right)$, ${\mathrm{Sn}}_{\mathrm{Zn}}\left(+/0\right)$, and $\left[{\mathrm{Cu}}_{\mathrm{Zn}}\text{−}{\mathrm{Sn}}_{\mathrm{Zn}}\right]\left(+/0\right)$ levels. We found that the effective recombination centers in CZTS, namely, ${{\mathrm{Sn}}_{\mathrm{Zn}}}^{2+}$ and ${\left[{\mathrm{Cu}}_{\mathrm{Zn}}\text{−}{\mathrm{Sn}}_{\mathrm{Zn}}\right]}^{+}$, have much smaller carrier capture rates in CZTSe, and are less detrimental to the minority carrier lifetime and energy conversion efficiency. The smaller carrier capture rates for CZTSe can be attributed to the higher electronic transition energies, lower phonon frequencies, and weaker electron-phonon coupling effects in CZTSe compared to those in CZTS, because the large Se cations give rise to larger lattice constants and a softer lattice in CZTSe.

中文翻译：

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Cu2ZnSnSe4中的缺陷辅助非辐射复合：与Cu2ZnSnS4的比较研究

的效率 ${铜}_2\mathrm{ZnSn}{硒}_4$ （CZTSe）在1.0 eV的带隙较窄的太阳能电池目前高于 ${铜}_2\mathrm{ZnSn}{\mathrm{小号}}_4$（CZTS），并根据Shockley-Queisser模型获得最佳带隙。为了理解这种异常观察，我们研究了由深部CZTSe中主要缺陷水平引起的非辐射复合率，即${锡}_{锌}（2+/+）$， ${锡}_{锌}（+/0）$， 和 $\left[{铜}_{锌}\text{-}{锡}_{锌}\right]（+/0）$水平。我们发现CZTS中的有效重组中心是${{锡}_{锌}}^{2+}$ 和 ${\left[{铜}_{锌}\text{-}{锡}_{锌}\right]}^{+}$在CZTSe中具有较小的载流子捕获率，并且对少数载流子寿命和能量转换效率的危害较小。与CZTSe相比，CZTSe较小的载流子捕获速率可归因​​于CZTSe中较高的电子跃迁能，较低的声子频率和较弱的电子-声子耦合效应，因为较大的Se阳离子会产生较大的晶格常数且较软CZTSe中的晶格。