三明治夹层结构设计实现外量子效率超过20%的发光场效应晶体管

论文

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速递

Light-emitting field-effect transistors with EQE over 20% enabled by a dielectric-quantum dots-dielectric sandwich structure

Lingmei Kong, Jialong Wu, Yunguo Li, Fan Cao, Feijiu Wang, Qianqian Wu, Piaoyang Shen, Chengxi Zhang, Yun Luo, Lin Wang, Lyudmila Turyanska, Xingwei Ding, Jianhua Zhang, Yongbiao Zhao, Xuyong Yang

Science Bulletin, 2022,67(5): 529–536

doi: 10.1016/j.scib.2021.12.013

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简介

新兴的量子点(QD)发光场效应晶体管(QLEFET)能够以较低成本产生高颜色纯度的发光, 并且其光电特性易于调节. 研究人员在设计器件结构和理解深层物理机制等方面已作了大量尝试, 但由于界面处的电荷/激子损耗和QD层与相邻载流子传输层之间存在着较大的能量势垒, 目前QLEFET的整体性能仍然偏低. 鉴于此, 本文采用一个介电层-QD-介电层的(DQD)的三明治夹层结构设计, 实现了外量子效率(EQE)超过20%的QLEFET. 该DQD结构可以通过调节能带排列进一步调控器件中载流子行为, 从而使激子复合区移动进入QD发光层. 此外, 通过抑制表面陷阱和界面电荷转移诱导的荧光猝灭引起的激子损耗, 有效提高了激子的辐射复合. 本研究提出的DQD夹层结构设计是一种改善QLEFET电致发光性能的全新概念, 也可以将其应用到其他材料体系中, 促进QD在新型光电器件中的开发应用.

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图文速览

Fig. 1 Device structure of QLEFETs with an emission layer of CdSe/ZnS QDs. (a) Schematic diagram of the device structure, (b) cross-sectional SEM image and (c) EDS compositional mapping images of a QLEFET with a DQD sandwiched structure. The scale bars are 100 nm. The thicknesses of Al₂O₃, ZnO, and PEDOT:PSS layerare ~ 150, 80 and 60 nm, respectively. (d) Representative high-resolution TEM images of cross-sections of (left) QDs/PEIE/PEDOT:PSS and (right) ZnO/MABr/QDs heterostructures.

Fig. 2 Performance characterizationof QLEFETs. (a) Normalized PL and EL spectra of QLEFET with a DQD sandwich structure. Inset: thephotograph of the operating devices with (top) and without (bottom) the DQDstructure. The emitting area is 1 mm × 0.05 mm at V_GS = −50 V. The scale bar is 400 μm. (b) Electrical transfer characteristicsof the QLEFETs. (c) Mott-Schottky plots of the control and QLEFETs with DQD structure. (d) Luminance (L)–V_GS and (e) EQE–V_GS of the QLEFETs. (f) Histogram of the maximum EQEs measured on 20 devices.

Fig. 3  Assessment of morphology and energy level alignment of the QD films. AFM images and a representative z-profile of (a) ZnO, (b) QDs and (c) QDs/PEIE films. UPS spectrain (d) secondary electron regionand (e) frontier electronic structure region of the QDs and the QDs/PEIE films. (f) Schematic diagram of energy level alignment in the PEIE modified QD films, where E_vac is the vacuum energy.

Fig. 4 Optical characteristics of the QDs/ZnO film and trap densities characteristics of the ZnO film. (a) PL spectra and (b) TRPL decay curves of the QDs, ZnO/QDs and ZnO/MABr/QDs films coated on the glass substrate. Spectra were acquired under excitation with 365 nm. (c) Ball-and-stick model of the top layer of (i) wurtzite ZnO(100) surface, (ii) ZnO (100) surface with adsorbed MABr, (iii) ZnO (100) surface with one Schottky defect and (iv) ZnO (100). surface with MABr adsorbed at the Schottky defect. (d) XPS spectra of the ZnO and ZnO/MABr films. (e) Current density (J)–V curves for devices with structures of ITO/ZnO/Al and ITO/ZnO/MABr/Al.

Fig. 5 Device structure and performance characterization of QLEDs. (a) Energy level diagram of the QLEDs. (b) Normalized EL and PL spectra, (c) J–V–L characteristics and (d) CE–J–EQE characteristics of QLEDs. Inset in (b): the photograph of the operating device with an emitting area of 2 mm × 2 mm at applied voltage of 7.5V.

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本文通讯作者

王飞久 教授  河南大学光伏材料省重点实验室. 主要从事低维材料制备, 非线性光学表征, 及光电子器件研究; 包括碳纳米管、石墨烯、与新型二维材料的制备、光学表征、以及其在光伏电池，晶体管等光电子器件方面的研究.

丁星伟  副研究员 上海大学新型显示技术与应用集成教育部重点实验室. 主要从事基于原子层沉积技术的氧化物薄膜晶体管和薄膜封装方面的研究工作. 

杨绪勇  教授  上海大学新型显示技术及应用集成教育部重点实验室. 主要从事发光材料与器件的研究, 尤其专长纳米发光材料与器件的研究.

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