[论文解读] Impacts of Fermi Level Pinning at Hole-Selective Contacts in CdSeTe/CdTe Solar Cells

Ariful Islam, Nathan D. Rock+4 more|arXiv (Cornell University)|Mar 7, 2026

Chalcogenide Semiconductor Thin Films被引用 0

一句话总结

该论文为 CdSeTe/CdTe 太阳能电池建立了一个器件物理模型，显示由供体样缺陷在 p 型 空穴接触处的费米能级钉扎主要降低填充因子，并探索钝化的空穴选择层以缓解带弯曲。

ABSTRACT

P-type doped CdTe free surfaces Schottky contacts, and even interfaces with isostructural p-ZnTe frequently exhibit downward band bending and moderate to high recombination velocities. Fermi level pinning by donor-like states can explain these band diagram features, as well as device response characteristics such as 1st quadrant rollover in current-voltage (JV) versus temperature (JVT). Parasitic downward band bending also produces voltage-dependent photocurrent collection, producing fill factor (FF) efficiency losses, JV dark/light non-superposition (or JV take-off), and irregularities in Jsc-Voc and Suns-Voc measurements. Herein, we develop a device physics model of state-of-the-art CdSeTe/CdTe solar cells consistent with known characterization of materials and devices, including the optical, thermalization, and trapping effects of band tail states and isolated defects. We use this model to demonstrate that Fermi-level pinning at the p-ZnTe/p-CdSeTe hole contact by donor-like defects reproduces the aforementioned observables, and conclude that (for contemporary few-um absorber thicknesses and low mobilities) it primarily affects FF rather than Voc. We investigate the performance gains possible from hypothetical passivated, hole-selective layers at the ZnTe/CdTe interface, which eliminate the downwards band bending caused by donor-like defects. For thinner devices and larger minority carrier diffusion lengths, these strategies will become more important for continued efficiency improvements.

研究动机与目标

• 理解 p 型 CdTe 自由表面和 p-ZnTe 界面的向下带弯曲与复合的动机
• 解释供体样缺陷态如何钉扎费米能级并引起观测到的器件行为
• 开发包含带尾态和与 CdSeTe/CdTe 器件相关的缺陷的基于物理的模型
• 评估在 ZnTe/CdTe 界面上假设的钝化空穴选择层对效率的潜在提升

提出的方法

• 构建一个器件物理模型，结合带尾态和孤立缺陷的光学、热化和捕获效应
• 模拟 p-ZnTe/p-CdSeTe 空穴接触处由供体样缺陷引起的费米能级钉扎
• 将模型预测与已知材料和器件表征进行比较
• 评估钉扎在不同 absorber 厚度与迁移率下对电压、电流和填充因子的影响
• 探讨移除向下带弯曲的钝化空穴选择层对性能的潜在提升

实验结果

研究问题

• RQ1 供体样缺陷引起的费米能级钉扎在空穴接触处如何影响 CdSeTe/CdTe 太阳能电池的 J-Vs/Voc 与 FF？
• RQ2 向下带弯曲在目前器件中对光电流收集及器件非理想性（J-V_T、Suns-Voc）有多大影响？
• RQ3 钝化的空穴选择界面是否能够缓解带弯曲并提升薄吸收层的器件性能？
• RQ4 在何种条件下（厚度、扩散长度、迁移率）钝化策略对效率提升的影响更显著？

主要发现

• 在 p-ZnTe/p-CdSeTe 空穴接触处的费米能级钉扎 reproduces observed band bending and recombination behavior.
• 在当前几微米吸收层、低迁移率的器件中，钉扎主要降低填充因子而非 Voc。
• 寄生向下带弯曲导致电压相关的光电流和非理想的 J-V 特性（暗/光 J-V 不可叠加，Suns-Voc 不规则）。
• 假设的在 ZnTe/CdTe 界面的钝化空穴选择层可消除向下带弯曲并改善性能。
• 对于更薄的器件和更大的少数载流子扩散长度，钝化策略对效率提升变得更为重要。