Hydrogen‐doped In₂O₃ (IOH) films are used as a transparent back contact in bifacial Cu(In,Ga)Se₂ (CIGS) solar cells. The effect of the IOH thickness and the impact of the sodium incorporation technique on the photovoltaic parameters are studied, and clear correlations are observed. It is shown that a loss in short circuit current density (J_SC) is the major limitation at back side illumination. The introduction of a thin Al₂O₃ layer on top of the IOH significantly increases the collection efficiency (ϕ(x)) for electrons generated close to the back contact. In this way, the J_SC loss can be mitigated to only ~ 25% as compared with front side illumination. The Al₂O₃ film potentially reduces the interface defect density or, alternatively, creates a field effect passivation. In addition, it prevents the excessive formation of Ga₂O₃ at the CIGS/IOH interface, which is found otherwise when a NaF layer is added before absorber deposition. Consequently, detrimental redistributions in Ga and In close to the back contact can be avoided. Finally, a bifacial CIGS solar cell with an efficiency (η) of η = 11.0% at front and η = 6.0% at back side illumination could be processed. The large potential for further improvements is discussed.

中文翻译：

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使用氢掺杂的In2O3薄膜作为透明背面触点的双面Cu（In，Ga）Se2太阳能电池

氢掺杂的In ₂ O ₃（IOH）薄膜用作双面Cu（In，Ga）Se ₂（CIGS）太阳能电池中的透明背接触。研究了IOH厚度的影响以及钠掺入技术对光伏参数的影响，并观察到明确的相关性。结果表明，短路电流密度（J _SC）的损失是背面照明的主要限制。在IOH顶部引入薄的Al ₂ O ₃层可显着提高靠近背触点产生的电子的收集效率（ϕ（x））。这样，J _SC与正面照明相比，损耗可减少至仅〜25％。Al ₂ O ₃膜可能会降低界面缺陷密度，或者产生场效应钝化。另外，它防止了在CIGS / IOH界面上过量形成Ga ₂ O ₃，否则在吸收体沉积之前添加NaF层时会发现这种情况。因此，可以避免Ga和In中靠近背接触的有害重新分布。最后，可以加工双面CIGS太阳能电池，其正面照明效率（η）为η= 11.0％，背面照明效率为（η= 6.0％）。讨论了进一步改进的巨大潜力。