Abstract In recent years CdTe thin film solar cells (SCs) have demonstrated promising market application foreground. However, a relatively large gap between the achieved SCs efficiencies and the theoretically predicted maximum efficiency still exists. In particular, the open circuit voltage (Voc) of the CdTe thin film SCs could be further increased, which is limited by high-work-function of CdTe. In this work, p-type narrow-gap SnTe thin films are proposed as a buffer layer in the back contact of CdTe SCs. The band alignment at SnTe/CdTe interface renders a small valance band offset, which expedites hole transport from the CdTe absorber to the hole electrode and improves the Ohmic contact for CdTe. With the insertion of a SnTe single buffer layer at the back contact, a Cu-free CdTe SC has been developed, which displays the same cell efficiency as the traditional cells using CuxTe as the back contact. The Voc of cells with ZnTe: Cu/SnTe double-layer at back contact is notably higher than the CdTe SCs fabricated with CuxTe or ZnTe: Cu single-layer at the back contact. Furthermore, accretion of hole concentration is also demonstrated by the diffusion of Sn in the CdTe absorber layer. This work shows the potential to improve CdTe SCs by using a narrow-gap IV-VI compound semiconductor.

中文翻译：

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具有背接触式 SnTe 缓冲层的 CdTe 薄膜太阳能电池

摘要 近年来，碲化镉薄膜太阳能电池（SCs）展现出广阔的市场应用前景。然而，实现的 SCs 效率与理论上预测的最大效率之间仍然存在相对较大的差距。特别是 CdTe 薄膜 SCs 的开路电压 (Voc) 可以进一步提高，这受到 CdTe 的高功函数的限制。在这项工作中，p 型窄隙 SnTe 薄膜被提议作为 CdTe SCs 背接触中的缓冲层。SnTe/CdTe 界面处的能带对齐呈现小的价带偏移，这加速了从 CdTe 吸收体到空穴电极的空穴传输，并改善了 CdTe 的欧姆接触。通过在背接触处插入 SnTe 单缓冲层，开发了无铜 CdTe SC，它显示出与使用 CuxTe 作为背接触的传统电池相同的电池效率。背面接触处具有 ZnTe:Cu/SnTe 双层的电池的 Voc 明显高于背面接触处使用 CuxTe 或 ZnTe:Cu 单层制造的 CdTe SC。此外，CdTe 吸收层中 Sn 的扩散也证明了空穴浓度的增加。这项工作显示了通过使用窄间隙 IV-VI 化合物半导体来改进 CdTe SCs 的潜力。