Quantum dot light emitting diodes using size-controlled ZnO NPs

김주성,강병호,정현민,김세완,Binrui Xu,강신원 한국물리학회 2018 Current Applied Physics Vol.18 No.6

The particle size and trap energy level of ZnO were adjusted by varying the concentration of precursors using a sol–gel process, and the energy transport properties of the electron transport layer in quantum dot light-emitting diodes (QD-LEDs) were analyzed. Thus far, no study has considered the efficient electron transport properties of quantum dot light-emitting devices with respect to trap energy levels owing to the oxygen vacancies of ZnO. The particle size and trap energy levels of ZnO were analyzed based on optical properties such as photoluminescence and absorbance. The optimized device showed excellent performance, with a maximum luminance of 50,120 cd/ m2, a high efficiency of 5.85 cd/A, and a threshold voltage of 2.5 V. The Y-ZnO (yellow photoluminescence ZnO)- based QD-LEDs not only enhanced the injection efficiency of electrons into the emitting layer but also confined the holes in the emitting layer due to the shallow trap level of Y-ZnO, in contrast to the deep trap levels of G-ZnO (green photoluminescence ZnO) and B-ZnO (blue photoluminescence ZnO). Here, we present the first attempt to analyze the electron transport behavior of the electron transport layer of the resulting device.

Human-robot Collision Detection Based on the Improved Camshift Algorithm and Bounding Box

Shuangning Lu,Zhouda Xu,Binrui Wang 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.10

Aiming at the problem of collision detection and collision point information evaluation in the process of human-robot collaboration, the binocular camera is used as an external sensor to observe. Collision detection is realized by tracking the motion of human-robot through the color information of joints. Firstly, the Camshift algorithm is used to track the position of the manipulator joints and the human arm joints based on the color information. In order to solve the factors that may cause target loss during tracking process, such as shelter and background color similar problems, Kalman filter is integrated on the basis of Camshift algorithm. A similarity threshold is set to judge whether there is interference in the tracking process. The tracking experiment proved that the Kalman filter is effective and enhances the robustness of the tracking algorithm. Secondly, a bounding box collision detection method based on space domain is designed. The sphere bounding box and the cylindrical bounding box is used as the human-robot bounding boxes. The equations of the distance between different boxes are derived and the position of the collision point on the manipulator is calculated. Finally, an experimental environment is built for verification. The distance error of the collision is within 0-10 mm, and the position error between the calculated collision point and the pre-determined collision point is within 10%.

Optimization of Cd2+ partial electrolyte treatment on the absorber layer for high-efficiency Cu2ZnSnSe4 solar cells

김옥식,권진범,김세완,Binrui Xu,배진혁,손대호,김영일,김세윤,김대환,강진규,강신원 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.80 No.-

Currently, many researchers are focused on promising new energy technologies such as Cu2ZnSnS4-basedsolar cells to replace fossil fuel sources. Investigations into a variety of methods have been done toanalyze the interfacial problems and improve the cell interfacial properties via a variety of methods. Inparticular, In order to improve the electrical performance of Cu2ZnSnSe4 (CZTSe) based solar cells, the Cdpartial electrolyte (Cd PE) treatment that is an effective method in CIGS solar cells prior to applying theirCdS buffer layer to their absorber layer has been studied. In our study, we investigated the Cd PEtreatment time, the Cd PE bath temperature, and the correlation between Cd PE treatment and CdSthickness. The optimum Cd PE absorber treatment was 7 min at 70 C, with a CdS layer of 35 nm thickdeposited cells. This combination increased photo-carrier collection in the short wavelength range andreduced absorber-buffer interface recombination. The efficiency of a 35 nm buffer layer sample withoutPE treatment was 8.90%. The efficiency of another 35 nm buffer layer sample was 10.38% (Voc: 441 mV,Jsc: 38.15 mA/cm2, and FF: 61.58%) after Cd PE treatment due to the increase of Jsc, FF and Rs despite thedeficit of Voc.

Enhancing the Photovoltaic Performance of Polymer Solar Cells by Manipulating Photoactive/Metal Interface

Jiang, Yu,Sai-Anand, Gopalan,Xu, Binrui,Lee, Jae-Sung,Kim, Sae-Wan,Yeom, Se-Hyuk,Bae, Jin-Hyuk,Kang, Shin-Won American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11

<P>In this work, a hybrid system composed of inorganic zinc oxide nanocrystals (ZnO NCs) and the organic conjugated polymer (poly[(9,9-bis(3'-(N, N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-( 9,9-dioctylfluorene)]) (PFN) was utilized as an electron selective interlayer (ESIL) to improve the electro-optical characteristics of bulk-heterojunction (BHJ) polymer solar cells (PSCs). To accomplish, water/alcohol-soluble cationic polyelectrolyte, PFN, was introduced into ZnO NCs (ZnO-PFN), aiming to enhance the electron extraction capability between the photoactive layer and the metal (Al) electrode in standard geometry BHJ PSCs. Importantly, the ZnO-PFN blend system achieved a higher power conversion efficiency (PCE) than pristine (ZnO NCs) ESILs. Moreover, an optimized photovoltaic (PV) performance was obtained with a low volume of PFN incorporated into the ZnO NCs ESIL. To validate the PV performance, PSCs were fabricated based on co-polymer of thienyl substituted BDT with TT:phenyl-C71-butyric acid methyl ester (PBDTTT-C-T:PC71BM) and poly(3-hexylthiophene-2,5-diyl): phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) photoactive systems and observed superior PV characteristics for ZnO-PFN hybrid ESILs. The optical transparency, microstructure, and morphological characteristics were evaluated using appropriate characterization techniques to demonstrate the superiority of the hybrid ZnO-PFN blend system. PSCs based on this ZnO-PFN composite based ESIL suggested an alternative practical approach to enhance the efficiency of the fabricated devices.</P>

New Structural Design of Gated Lateral Bipolar Junction Transistor for Sensor Applications

Jeong, Hyun-Min,Kwon, Jin-Beom,Kwon, Hyurk-Choon,Kim, Ju-Seong,Xu, Binrui,Kwon, Dae-Hyuk,Kang, Shin-Won Institute of Electrical and Electronics Engineers 2018 IEEE transactions on electron devices Vol.65 No.1

<P>In this paper, we propose a gated lateral bipolar junction transistor (GLBJT) that has a cascade structure, resulting in improved sensing performance over conventional GLBJTs. The device can be operated in bipolar junction transistor (BJT) mode, metal–oxide–semiconductor field-effect transistor (MOSFET) mode, and a hybrid MOSFET-BJT mode under input bias control. The device exhibits higher transconductance than that of conventional GLBJTs owing to the cascade structure using pMOSFET. The cascade effect generated in the proposed device is shown to increase the transconductance, and the results from two experiments [pH response and C-reactive protein (CRP)-antigen detection] demonstrate that the sensitivity of the proposed sensor exceeds that of conventional GLBJTs. The proposed device offers approximately 2.5 times that the sensitivity of conventional GLBJTs in the pH and CRP-antigen detection experiments. These results confirm that the proposed device has enhanced sensitivity and suggests the possibility of realizing more efficient sensors with better sensitivity than that of conventional GLBJTs.</P>

Quantum dot light emitting diodes using size-controlled ZnO NPs

Kim, Ju-Seong,Kang, Byoung-Ho,Jeong, Hyun-Min,Kim, Sae-Wan,Xu, Binrui,Kang, Shin-Won ELSEVIER 2018 Current Applied Physics Vol.18 No.6

<P><B>Abstract</B></P> <P>The particle size and trap energy level of ZnO were adjusted by varying the concentration of precursors using a sol–gel process, and the energy transport properties of the electron transport layer in quantum dot light-emitting diodes (QD-LEDs) were analyzed. Thus far, no study has considered the efficient electron transport properties of quantum dot light-emitting devices with respect to trap energy levels owing to the oxygen vacancies of ZnO. The particle size and trap energy levels of ZnO were analyzed based on optical properties such as photoluminescence and absorbance. The optimized device showed excellent performance, with a maximum luminance of 50,120 cd/m<SUP>2</SUP>, a high efficiency of 5.85 cd/A, and a threshold voltage of 2.5 V. The Y-ZnO (yellow photoluminescence ZnO)-based QD-LEDs not only enhanced the injection efficiency of electrons into the emitting layer but also confined the holes in the emitting layer due to the shallow trap level of Y-ZnO, in contrast to the deep trap levels of G-ZnO (green photoluminescence ZnO) and B-ZnO (blue photoluminescence ZnO). Here, we present the first attempt to analyze the electron transport behavior of the electron transport layer of the resulting device.</P>

Stable hybrid organic/inorganic multiple-read quantum-dot memory device based on a PVK/QDs solution

Kim, Sae-Wan,Kwon, Jin-Beom,Kim, Na-Ri,Lee, Jae-Sung,Lee, Sang-Won,Kang, Byoung-Ho,Kim, Ju-Seong,Xu, Binrui,Bae, Jin-Hyuk,Kang, Shin-Won Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.481 No.-

<P><B>Abstract</B></P> <P>A thin-film memory device is proposed herein, based on quantum dots (QDs) with bi-stable characteristics under a positive voltage bias. The synthesized QDs had a CdSe/ZnS core/shell structure. The charge confinement effect within the QDs in the charge-storage layer was enhanced by adding (poly(9-vinylcarbazole)) (PVK). As the PVK concentration increases, the on/off ratio of the device increases. Noise was also reduced and stable I-V characteristics were demonstrated. Each thin film was fabricated by a spin-coating method, among solution process methods. The on/off ratio of the fabricated device was found to be maximum 378 × 10<SUP>3</SUP> at 1.5 wt% PVK concentration. The initial on/off state was maintained even when a negative voltage (commonly used for the “erase” function) was applied. In addition, the write voltage of the fabricated device using the conductive polymer poly-TPD was reduced from 2.8 to 1.7 V. By optimizing PVK concentration and forming the poly-TPD thin film, the fabricated memory device had an on/off ratio of about 4 × 10<SUP>3</SUP> at 0.5 V and the stored current maintained the initial value even after 200 h. Even with a single write process, the initially formed high state is maintained for more than 200 h, and it is possible to read repeatedly.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The multiple-read memory device based on quantum dots (QDs) and poly-vinyl carbazole (PVK) blended solutions was developed. </LI> <LI> The optimized concentration of PVK was 1.5 wt%, and then the on/off ratio was 378×10<SUP>3</SUP>, and the write voltage was 2.8 V. </LI> <LI> By using conductive polymer poly-TPD, write voltage can be reduced from 2.8 to 1.7 V. </LI> <LI> The stored current maintained the initial value even after 200 hours. </LI> </UL> </P>