The hole transport layer (HTL)-free carbon electrode-based perovskite solar cells (C-PSCs) possess promising commercial application potential due to their fascinating advantages of low cost and high stability. However, the large energy level mismatch between perovskite and carbon electrodes seriously restricts the photovoltaic performance. 3D/2D perovskite heterostructures have been widely adopted to regulate energy level alignment, whereas achieving a large built-in electric field (V_bi) is still a great challenge. Herein, we propose molecular dipole moment engineering to regulate the interface energy levels and V_bi of 3D/2D perovskite heterojunctions. Experimental and theoretical results demonstrate that an organic cation with ultra-large dipole moment significantly improves the work function of 2D perovskites, resulting in the formation of p-type 2D perovskites. Besides, an ultra-thick (>200 nm) 2D perovskite layer is constructed on the surface of the 3D perovskite film. This results in the construction of 3D/2D p–n junctions, significantly enhancing the V_bi. As a result, the formed powerful 3D/2D heterojunction not only effectively passivates the defect states, but also markedly promotes the extraction of photogenerated holes. The devices achieve a new record efficiency of 20.08% (certified 19.6%) for HTL-free C-PSCs. The unencapsulated devices maintain 96% of the initial value after operating for 1000 h at maximum power point.

中文翻译：

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用于高效碳基钙钛矿太阳能电池的超大偶极矩有机阳离子衍生的3D/2D p-n异质结


无空穴传输层（HTL）的碳电极基钙钛矿太阳能电池（C-PSC）由于其低成本和高稳定性的迷人优势而具有广阔的商业应用潜力。然而，钙钛矿和碳电极之间巨大的能级不匹配严重限制了光伏性能。 3D/2D钙钛矿异质结构已被广泛采用来调节能级排列，但实现大的内置电场（V _bi ）仍然是一个巨大的挑战。在此，我们提出分子偶极矩工程来调节3D/2D钙钛矿异质结的界面能级和V _bi 。实验和理论结果表明，具有超大偶极矩的有机阳离子显着提高了二维钙钛矿的功函数，从而形成了p型二维钙钛矿。此外，在3D钙钛矿薄膜的表面构建了超厚（>200 nm）2D钙钛矿层。这导致了 3D/2D p-n 结的构建，显着增强了 V _bi 。结果，形成的强大的3D/2D异质结不仅有效地钝化了缺陷态，而且显着促进了光生空穴的提取。该器件在无 HTL C-PSC 方面实现了 20.08% 的新纪录效率（认证为 19.6%）。未封装的器件在最大功率点运行 1000 小时后仍保持初始值的 96%。