The performance‐boosting effect of alkali treatments is well known for chalcogenide thin‐film solar cells based on Cu(In,Ga)Se₂ (CIGS) and Cu₂ZnSn(S,Se)₄ (CZTSSe–kesterite) absorbers. In contrast to heavier alkali elements, lithium is expected to alloy with the kesterite phase leading to the solid solution (Li_xCu_1−x)₂ZnSn(S,Se)₄ (LCZTSSe), which offers a way of tuning the semiconductor bandgap by changing the ratio Li/(Li+Cu). Here is presented an experimental series of solution‐processed LCZTSSe with lithium fraction Li/(Li+Cu) ranging from x = 0 to 0.12 in the selenized absorber as measured by means of inductively coupled plasma mass spectrometry. The proportional increase in lattice parameter a and bandgap from 1.05 to 1.18 eV confirms the lithium alloying in the kesterite phase. Increase in grain size is observed for x up to 0.07, whereas a higher lithium fraction leads to a porous absorber morphology due to an inhomogeneous distribution of Li‐containing compounds in the kesterite layer. An increase of the photoluminescence quantum yield is observed as the Li fraction increases in the absorber layer. A champion device exhibits a remarkable efficiency of 11.6% (12.2% active area) for x = 0.06, close to the world record value of 12.6% demonstrating the effectiveness of lithium alloying.

中文翻译：

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锂合金化的高效（LixCu1-x）2ZnSn（S，Se）4钾盐型太阳能电池

对于基于Cu（In，Ga）Se ₂（CIGS）和Cu ₂ ZnSn（S，Se）₄（CZTSSe-kesterite）吸收剂的硫属化物薄膜太阳能电池，碱处理的性能提升作用是众所周知的。与较重的碱金属元素相反，锂有望与钾钛矿相形成合金，从而形成固溶体（Li _x Cu _{1- x}）₂ ZnSn（S，Se）₄（LCZTSSe），这提供了一种调节半导体带隙的方法通过改变比率Li /（Li + Cu）。此处介绍了一系列锂溶液中Li /（Li + Cu）范围为x的固溶LCZTSSe实验借助于电感耦合等离子体质谱法测得的硒化吸收剂的浓度为0到0.12。晶格参数a和带隙从1.05 eV到1.18 eV的成比例增加，证实了锂镁橄榄石相的合金化。x达到0.07时，晶粒尺寸会增加，而较高的锂含量会导致多孔吸收体形貌，这是由于含锂化合物在钾钛矿层中的分布不均匀所致。随着吸收层中Li分数的增加，观察到光致发光量子产率的增加。当x = 0.06时，冠军设备的效率高达11.6％（有效面积为12.2％），接近世界纪录的12.6％，证明了锂合金的有效性。