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Influence of Disassociation Probability on external quantum efficiency in Organic Electrophosphorescent Devices

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Semiconductor Photonics and Technology 2007年第3期13卷 181-185页

作者： ZHANG Jian-hua OU YANG Jun LI Xue-yong LI Hong-jian Department of Physics Xiangnan University Chenzhou 423000 CHN College of Physics Science and Technology Central South University Changsha 410083 CHN

An analytical model is presented to calculate the disassociation probability and the external quantum efficiency at high field in doped organic electrophosphorescence(EPH) devices. The charge recombination process and the triplet(T)-triplet(T) annihilation processes are taken into account in this model. The influences of applied voltage and the thickness of the device on the disassociation probability, and of current density and the thickness of the device on the external quantum efficiency are studied thoroughly by including and ignoring the disassociation of excitons. It is found that the dissociation probability of excitons will come close to 1 at high electric field, and the external EPH quantum efficiency is almost the same at low electric field. There is a large discrepancy of the external EPH quantum efficiency at high electric field for including or ignoring the disassociation of excitons.

关键词： electrophosphorescence disassociation probability triplet external quantum efficiency

Calculation and Improvement on external quantum efficiency of OLEDs

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Semiconductor Photonics and Technology 2006年第1期12卷 1-4页

作者： LI Chuan-nan XIE Wen-fa LIU Shi-yong College of Electronics Science and Engineering State Key Laboratory of Integrated Optoelectronics Jilin University Changchun 130012 CHN

The calculation of the external quantum efficiency(η_ ext ) of organic light-emitting devices(OLEDs) is presented theoretically. The basic idea is to obtain η_ ext by calculating the fraction of the generated light that can escape through the top surface and the average transmittance over the escape cone. During the calculation, the effects of the interference, absorption and multiple reflections are neglected. Then a result of a typical 8-tris-hydroxyquinoline aluminum(Alq_ 3 )-based OLEDs on a planar glass substrate is obtained. And a twice increase in η_ ext can be achieved by using a high-index-glass substrate with an antireflection coating(SiO_ 2 ) on substrate surface.

关键词： external quantum efficiency OLEDs Average transmittance Antireflection coating

Broadband photomultiplication-type polymer photodetectors and its application in light-controlled circuit

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Science China Chemistry 2022年第8期65卷 1642-1649页

作者： Ming Liu Qunping Fan Kaixuan Yang Zijin Zhao Xingchao Zhao Zhengji Zhou Jian Zhang Francis Lin Alex K.-Y.Jen Fujun Zhang Key Laboratory of Luminescence and Optical Information Ministry of EducationBeijing Jiaotong UniversityBeijing 100044China Department of Chemistry City University of Hong KongHong Kong 999077China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China Key Lab for Special Functional Materials Ministry of EducationNational and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technologyand School of MaterialsHenan UniversityKaifeng 475004China Guangxi Key Laboratory of Information Materials School of Material Science and TechnologyGuilin University of Electronic TechnologyGuilin 541004China Department of Materials Science and Engineering City University of Hong KongHong Kong 999077China Department of Materials Science and Engineering University of WashingtonWashington 98195-2120United States Hong Kong Institute for Clean Energy City University of Hong KongHong Kong 999077China

Photomultiplication-type polymer photodetectors(PM-PPDs)were achieved with polymer P3HT as donor and PY3Se-1V as acceptor based on structure of ITO/PEDOT:PSS/active layer/*** optimal weight ratio of P3HT to PY3Se-1V is about 100:*** of isolated electron traps are formed with PY3Se-1V surrounded by P3HT due to rather less content of PY3Se-1V in active layers and about 0.94 e V energy offset between the lowest unoccupied molecular orbitals(LUMO)of P3HT and *** optimal PM-PPDs exhibit broad spectral response from 350 to 950 nm and external quantum efficiency(EQE)values of68,200%at 360 nm,26,400%at 630 nm and 19,500%at 850 nm under-15 V *** working mechanism of PM-PPDs is attributed to the interfacial trap-assisted hole tunneling injection from external *** performance of PM-PPDs can be further improved by incorporating appropriate PMBBDT with high hole mobility as the third *** EQE values of optimal ternary PM-PPDs are increased to 105,000%at 360 nm,40,000%at 630 nm and 31,800%at 850 nm under-15 V bias,benefiting from the enhanced hole transport in ternary active *** optimal ternary PM-PPDs were successfully applied in a light-controlled circuit to turn on or turn off light emitting diode(LED).

关键词： polymer photodetectors photomultiplication external quantum efficiency broadband

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Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well solar cells

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Chinese Physics B 2014年第6期23卷 629-634页

作者：杨静赵德刚江德生刘宗顺陈平李亮吴亮亮乐伶聪李晓静何晓光王辉朱建军张书明张宝顺杨辉 State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Sciences

Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well （MQW） solar cells are investigated. It is found that due to the reduction of piezoelectric polarization and the enhancement of tunneling transport of photo-generated carriers in MQWs, the external quantum efficiency （EQE） of the solar cells increases in a low energy spectral range （λ 〉 370 nm） when the barrier thickness value decreases from 15 nm to 7.5 nm. But the EQE decreases abruptly when the barrier thickness value decreases down to 3.75 nm. The reasons for these experimental results are analyzed. We are aware that the reduction of depletion width in MQW region, caused by the high resistivity of the p-type GaN layer may be the main reason for the abnormally low EQE value at long wavelengths （λ 〉 370 nm）.

关键词： nitride materials external quantum efficiency polarization p-type GaN resistivity

Chiral multiple-resonance thermally activated delayed fluorescence materials based on chiral spiro-axis skeleton for efficient circularly polarized electroluminescence

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Science China Chemistry 2024年第7期67卷 2257-2264页

作者： Shi-Quan Song Xiao Han Zhong-Zhong Huo Ching-Fai Yip Xian-Fang Hong Meng-Ning Ding You-Xuan Zheng State Key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic MaterialsSchool of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China Key Laboratory of Mesoscopic Chemistry of Ministry of Education School of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China

Chiral luminescence materials have potential applications in the field of three-dimensional displays due to their circularly polarized luminescence(CPL)***,the further development of circularly polarized organic light-emitting diodes(CP-OLEDs)needs to meet the requirements of high efficiency,high color purity,low cost,and high dissymmetry factor(gPLor gEL),chiral multiple resonance thermally activated delayed fluorescence(MR-TADF)materials are considered as candidates in these ***,based on a pair of chiral spirofluorene precursors,two pairs of high-performance chiral MR-TADF emitters((R/S)-p-Spiro-DtBuCzB and(R/S)-m-Spiro-DtBuCzB)are developed,which exhibit strong emissions peaking at 491 and 502 nm in toluene with full-width at half-maximum values of 25 and 33 nm,*** addition,small singlet–triplet energy gaps of 0.15 and 0.10 eV with high absolute photoluminescence efficiencies of 95.0%and 96.7%are observed for p-Spiro-DtBuCzB and m-Spiro-DtBuCzB molecules,*** based on p-Spiro-DtBuCzB and m-Spiro-DtBuCzB display high maximum external quantum efficiencies of 29.6%and 33.8%,*** importantly,CP-OLEDs present symmetric circularly polarized electroluminescence spectra with|gEL|factors of 3.36×10^(-4)and 7.66×10^(-4)for devices based on(R/S)-p-Spiro-DtBuCzB and(R/S)-m-Spiro-DtBuCzB enantiomers,respectively.

关键词： chiral spiro-axis skeleton-based material multiple resonance thermally activated delayed fluorescence circularly polarized electroluminescence dissymmetry factor external quantum efficiency

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A GQD-based composite film as photon down-converter in CNT/Si solar cells

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Nano Research 2021年第11期14卷 3893-3899页

作者： Xuewei Zhao Yizeng Wu Zhiyuan Xia Shulong Chang Yuanyuan Shang Anyuan Cao School of Materials Science and Engineering Peking UniversityBeijing100871China School of Physics and Microelectronics Zhengzhou UniversityZhengzhou450001China

Graphene quantum dots (GQDs), have unique quantum confinement effects, tunable bandgap and luminescence property, with a wide range of potential applications such as optoelectronic and biomedical areas. However, GQDs usually have a strong tendency toward aggregation especially in making solid films, which will degrade their optoelectronic properties, for example, causing undesired fluorescence quenching. Here, we designed a composite film by embedding GQDs in a polyvinyl pyrrolidone (PVP) matrix through hydrogen bonding with well-preserved fluorescence, with a small addition of acid for compensating the poor conductivity of PVP. As a multifunctional solid coating on carbon nanotube/silicon (CNT/Si) solar cells, the photon down-conversion by GQDs and the PVP anti-reflection layer for visible light lead to enhanced external quantum efficiency (by 12.34% in the ultraviolet (UV) range) and cell efficiency (up to 14.94%). Such advanced optical managing enabled by low-cost, carbon-based quantum dots, as demonstrated in our results, can be applied to more versatile optoelectronic and photovoltaic devices based on perovskites, organic and other materials.

关键词： graphene quantum dots polyvinyl pyrrolidone energy-down-shift external quantum efficiency CNT/Si solar cells

Chemical regulation of metal halide perovskite nanomaterials for efficient light-emitting diodes

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Science China Chemistry 2018年第9期61卷 1047-1061页

作者： Kun-Hua Wang Bai-Sheng Zhu Ji-Song Yao Hong-Bin Yao Division of Nanomatenals & Chemistry Hefei National Laboratory for Physical Sciences at Microscale University of Science and Technology of China Hefei 230026 China Department of Chemistry University of Science and Technology of China Hefei 230026 China

Metal halide perovskite nanomaterials emerged as attractive emitting materials for light-emitting diodes(LEDs) devices due to their high photoluminescence quantum yield(PLQY), narrow bandwidth, high charge-carrier mobility, bandgap tunability, and facile synthesis. In the past few years, it has been witnessed an unprecedented advance in the field of metal halide perovskite nanomaterials based LEDs(Pe LEDs) with a rapid external quantum efficiency(EQE) increase from 0.1% to 14.36%. From the viewpoint of material chemistry, the chemical regulation of metal halide perovskite nanomaterials made a great contribution to the efficiency improvement of Pe LEDs. In this review, we categorize the strategies of chemical regulation as A-site cation engineering, B-site ion doping, X-site ion exchange, dimensional confinement, ligand exchange, surface passivation and interface optimization of transport layers for improving the EQEs of Pe LEDs. We also show the potentials of chemical regulation strategies to enhance the stability of Pe LEDs. Finally, we present insight toward future research directions and an outlook to further improve EQEs and stabilities of Pe LEDs aiming to practical applications.

关键词： chemical regulation metal halide perovskite nanomaterials light-emitting diodes external quantum efficiency

Infrared light-emitting diodes based on colloidal Pb Se/Pb S core/shell nanocrystals

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Chinese Physics B 2020年第1期29卷 482-488页

作者： Byung-Ryool Hyun Mikita Marus Huaying Zhong Depeng Li Haochen Liu Yue Xie Weon-kyu Koh Bing Xu Yanjun Liu Xiao Wei Sun Guangdong University Key Laboratory for Advanced quantum Dot Displays and Lighting Shenzhen Key Laboratory for Advanced Quantum Dot Displays and LightingDepartment of Electrical&Electronic EngineeringSouthern University of Science and TechnologyShenzhen 518055China School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore Shenzhen Planck Innovation Technologies Co.Ltd Shenzhen 518112China

Colloidal Pb Se nanocrystals(NCs)have gained considerable attention due to their efficient carrier multiplication and emissions across near-infrared and short-wavelength infrared spectral ***,the fast degradation of colloidal Pb Se NCs in ambient conditions hampers their widespread applications in infrared *** is well-known that the inorganic thick-shell over core improves the stability of ***,we present the synthesis of Pb Se/Pb S core/shell NCs showing wide spectral tunability,in which the molar ratio of lead(Pb)and sulfur(S)precursors,and the concentration of sulfur and Pb Se NCs in solvent have a significant effect on the efficient Pb S shell *** infrared light-emitting diodes(IR-LEDs)fabricated with the Pb Se/Pb S core/shell NCs exhibit an external quantum efficiency(EQE)of 1.3%at 1280 *** ligand exchange to optimize the distance between NCs and chloride treatment are important processes for achieving high performance on Pb Se/Pb S *** results provide evidence for the promising potential of Pb Se/Pb S NCs over the wide range of infrared optoelectronic applications.

关键词： Pb Se/Pb S core/shell nanocrystal ligand exchange infrared light-emitting diodes external quantum efficiency

Green light-emitting diodes based on hybrid perovskite films with mixed cesium and methylammonium cations

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Nano Research 2017年第4期10卷 1329-1335页

作者： Junjie Si Yang Liu Nana Wang Meng Xu Jing Li Haiping He Jianpu Wang Yizheng Jin State Key Laboratory of Silicon Materials Center for Chemistry of High-Performance & Novel Materials School of Materials Science and Engineering Zhejiang University Hangzhou 310027 China Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM) Nanjing Tech University (NanjingTech) 30 South Puzhu Road Nanjing 211816 China State Key Laboratory of Silicon Materials School of Materials Science and Engineering Zhejiang University Hangzhou 310027 China Center for Chemistry of High-Performance & Novel Materials State Key Laboratory of Silicon Materials Department of ChemistryZhejiang University Hangzhou 310027 China

We report the formation of high-quality Cs0.4MA0.6PbBr3 thin films with nearly full surface coverage and good emission properties upon the introduction of Cs^＋ into perovskite crystals. The Cs0.4MA0.6PbBr3 thin films were applied as emissive layers in light-emitting diodes. A maximum external quantum efficiency of -2.0% was achieved for these green-emitting devices.

关键词： perovskite light-emitting diodes cesium emission properties external quantum efficiency