The crucial separation of photocarriers in solar cells can be efficiently driven by contacting semiconductor phases with differing doping levels. Here we show that intrinsic doping surges in methylammonium lead iodide (MAPbI₃) crystals as a response to environmental basicity. MAPbI₃ crystals were passivated with polybases to induce the deprotonation of its methylammonium ions (MA⁺). Stable crystals showed marked increases in photoluminescence and radiative decay, attributed to the presence of unbalanced charges acting as doped carriers. This emulates in a controlled manner the proton-withdrawing conditions of polycrystalline films, where excess basic precursors are found between grains. Raman spectroscopy showed the collective alignment of MA⁺ cations within the intrinsically doped lattices, thus revealing the buildup of electric fields. On this basis, we propose a mechanism for the formation of doping-gradients toward grain boundaries, potentially explaining the extended photocarrier lifetimes and diffusion lengths observed in perovskite solar cells.

中文翻译：

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混合有机-无机钙钛矿中质子的迁移触发了本征掺杂

通过使具有不同掺杂水平的半导体相接触，可以有效地驱动太阳能电池中光载流子的关键分离。在这里，我们表明甲基铵碘化铅（MAPbI ₃）晶体中的固有掺杂激增是对环境碱性的响应。MAPbI ₃晶体用多碱钝化以诱导其甲基铵离子（MA ⁺）的去质子化。稳定的晶体显示出光致发光和辐射衰减的显着增加，这归因于不平衡电荷作为掺杂载流子的存在。这以可控的方式模拟了多晶膜的质子吸收条件，其中在晶粒之间发现了过量的碱性前体。拉曼光谱显示MA ⁺的集体排列本征掺杂晶格中的阳离子，从而揭示了电场的建立。在此基础上，我们提出了一种向晶界形成掺杂梯度的机制，可能解释了钙钛矿型太阳能电池中观察到的延长的光载流子寿命和扩散长度。