Ultrathin single- and three-stage Cu(In,Ga)Se2 absorber layers were analyzed with room temperature photoluminescence (PL) spectra. An anomalous blueshift was observed upon increasing carrier injection for both samples. This blueshift was attributed to the presence of bandgap fluctuations that are of the same order as the minority carrier diffusion length. From time resolved measurements, a diffusion length of a few 100 nms was deduced. The single-stage spectrum consists of two peaks, and the sample was, therefore, also analyzed by hyperspectral imaging, providing lateral PL and reflectance data with 1 μm resolution. Marginal variations were observed in the PL yield and spectra. This homogeneity could again be attributed to an intermediate scale of the bandgap fluctuation with an upper limit of 1 μm for the scale of the lateral bandgap fluctuations. The two peaks in the PL spectra of the single-stage sample could be attributed to interference, and correction methods were applied. The bandgap fluctuations were extracted for the three-stage and single-stage sample and were 45 meV and 72 ± 3 meV, respectively. It is suggested that this difference is attributed to the smaller grains and larger amount of grain boundaries in the single-stage sample.

中文翻译：

---

超薄 Cu(In,Ga)Se2 吸收层中的中等尺度带隙波动

使用室温光致发光 (PL) 光谱分析超薄单级和三级 Cu(In,Ga)Se2 吸收层。在增加两种样品的载流子注入后观察到异常蓝移。这种蓝移归因于与少数载流子扩散长度具有相同数量级的带隙波动的存在。从时间分辨测量中，推导出了几个 100 nm 的扩散长度。单级光谱由两个峰组成，因此还通过高光谱成像分析了样品，提供了分辨率为 1 μm 的横向 PL 和反射率数据。在 PL 产率和光谱中观察到边际变化。这种均匀性可以再次归因于带隙波动的中间尺度，横向带隙波动的尺度上限为 1 μm。单级样品的 PL 光谱中的两个峰可能归因于干扰，并应用了校正方法。提取了三级和单级样品的带隙波动，分别为 45 meV 和 72 ± 3 meV。这表明这种差异归因于单级样品中更小的晶粒和更多的晶界。