Sun Bin, Najarian Amin Morteza, Sagar Laxmi Kishore, Biondi Margherita, Choi Min-Jae, Li Xiyan, Levina Larissa, Baek Se-Woong, Zheng Chao, Lee Seungjin, Kirmani Ahmad R, Sabatini Randy, Abed Jehad, Liu Mengxia, Vafaie Maral, Li Peicheng, Richter Lee J, Voznyy Oleksandr, Chekini Mahshid, Lu Zheng-Hong, García de Arquer F Pelayo, Sargent Edward H
Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, M5S 1A4, Canada.
Materials Science and Engineering Division, National Institute of Standards and Technology (NIST), Gaithersburg, MD, 20899, USA.
Adv Mater. 2022 Aug;34(33):e2203039. doi: 10.1002/adma.202203039. Epub 2022 Jul 17.
Colloidal quantum dots (CQDs) are promising materials for infrared (IR) light detection due to their tunable bandgap and their solution processing; however, to date, the time response of CQD IR photodiodes is inferior to that provided by Si and InGaAs. It is reasoned that the high permittivity of II-VI CQDs leads to slow charge extraction due to screening and capacitance, whereas III-Vs-if their surface chemistry can be mastered-offer a low permittivity and thus increase potential for high-speed operation. In initial studies, it is found that the covalent character in indium arsenide (InAs) leads to imbalanced charge transport, the result of unpassivated surfaces, and uncontrolled heavy doping. Surface management using amphoteric ligand coordination is reported, and it is found that the approach addresses simultaneously the In and As surface dangling bonds. The new InAs CQD solids combine high mobility (0.04 cm V s ) with a 4× reduction in permittivity compared to PbS CQDs. The resulting photodiodes achieve a response time faster than 2 ns-the fastest photodiode among previously reported CQD photodiodes-combined with an external quantum efficiency (EQE) of 30% at 940 nm.
胶体量子点（CQDs）因其可调谐带隙和溶液加工特性，是用于红外（IR）光检测的有前景的材料；然而，迄今为止，CQD红外光电二极管的时间响应不如硅和铟镓砷提供的响应。据推断，II-VI族CQDs的高介电常数由于屏蔽和电容导致电荷提取缓慢，而III-V族——如果其表面化学能够掌握——具有低介电常数，因此增加了高速运行的潜力。在初步研究中，发现砷化铟（InAs）中的共价特性导致电荷传输不平衡，这是未钝化表面和不受控制的重掺杂的结果。报道了使用两性配体配位的表面管理方法，并且发现该方法同时解决了In和As表面的悬空键。新型InAs CQD固体结合了高迁移率（0.04 cm² V⁻¹ s⁻¹），与PbS CQDs相比，介电常数降低了4倍。由此产生的光电二极管实现了快于2 ns的响应时间——这是此前报道的CQD光电二极管中最快的——并在940 nm处具有30%的外量子效率（EQE）。
