Cahen David, Rakita Yevgeny, Egger David A, Kahn Antoine
Dept. of Mol. Chem. & Materials Science, Weizmann Institute of Science, Herzl 234, Rehovot, 7610001, Israel.
Department of Materials Engineering, Ben Gurion University of the Negev, Be'er Sheva, 8410501, Israel.
Adv Mater. 2024 Dec;36(50):e2407098. doi: 10.1002/adma.202407098. Epub 2024 Oct 31.
The (opto)electronic behavior of semiconductors depends on their (quasi-)free electronic carrier densities. These are regulated by semiconductor doping, i.e., controlled "electronic contamination". For metal halide perovskites (HaPs), the functional materials in several device types, which already challenge some of the understanding of semiconductor properties, this study shows that doping type, density and properties derived from these, are to a first approximation controlled via their surfaces. This effect, relevant to all semiconductors, and already found for some, is very evident for lead (Pb)-HaPs because of their intrinsically low electrically active bulk and surface defect densities. Volume carrier densities for most polycrystalline Pb-HaP films (<1 µm grain diameter) are below those resulting from even < 0.1% of surface sites being electrically active defects. This implies and is consistent with interfacial defects controlling HaP devices in multi-layered structures with most of the action at the two HaP interfaces. Surface and interface passivation effects on bulk electrical properties are relevant to all semiconductors and are crucial for developing those used today. However, because bulk dopant introduction in HaPs at controlled ppm levels for electronic-relevant carrier densities is so difficult, passivation effects are vastly more critical and dominate, to first approximation, their optoelectronic characteristics in devices.
半导体的（光）电子行为取决于其（准）自由电子载流子密度。这些载流子密度通过半导体掺杂来调节，即受控的“电子污染”。对于金属卤化物钙钛矿（HaPs）这种已对某些半导体特性的理解提出挑战的多种器件类型中的功能材料，本研究表明，掺杂类型、密度以及由此衍生的特性，在一阶近似下是通过其表面来控制的。这种对所有半导体都相关且已在某些半导体中发现的效应，对于铅（Pb）-HaPs 尤为明显，因为它们本质上电活性体缺陷和表面缺陷密度较低。大多数多晶 Pb-HaP 薄膜（晶粒直径<1 µm）的体载流子密度低于即使表面位点中<0.1%为电活性缺陷时所产生的载流子密度。这意味着且与界面缺陷控制多层结构中的 HaP 器件一致，其中大部分作用发生在两个 HaP 界面处。表面和界面钝化对体电学性质的影响与所有半导体相关，并且对于开发当今使用的半导体至关重要。然而，由于在 HaPs 中以受控的 ppm 水平引入与电子相关的载流子密度的体掺杂剂非常困难，钝化效应在一阶近似下更为关键，并主导了它们在器件中的光电特性。
