Promoting academic excellence and development world class research centers

國立成功大學「發展國際一流大學及頂尖研究中心計畫」

  延攬優秀人才工作報告表

NCKU Project of Promoting Academic Excellence & Developing World Class Research Centers

Work Report Form for Distinguished Scholars

□續聘

■離職

Name of the Employee

Mora Veera Madhava Rao 男 女 Male Female 聘　期 Period of Employment from 2011 年(y)　01 月(m)01 日(d) to 2011 年(y) 03 月(m)31 日(d) 研究或教學或科技研發與 管理計畫名稱 The project title of research,

teaching, technology development and management

Promoting academic

excellence and development world class research centers

計畫主持人 （申請單位主管） Project Investigator (Head of Department/Center) Prof. Yan-Kuin Su 補助延聘編號

Grant Number

HUA100-3-15-032

一、

（由受聘人填寫）

Please summarize the entire research, teaching, or science and technology R&D and management work process (To be completed

by the employee)

1) (Bi0.5Na0.5)0.93Ba0.07TiO3 lead-free ceramics with addition of Ga2O3 (Physica B 403 (2008) 3596– 3598)

(M.V. Madhava Rao, Chen-Feng Kao)

As a candidate of a lead-free (Bi0.5Na0.5TiO3)0.93(BaTiO3)0.07+ x wt% Ga2O3 with x 1 0.0–0.2 has been synthesized by solid-state sintering ceramic-fabrication technique. The effect of Ga2O3 addition with ceramics enhanced the dielectric constant of free (Bi0.5Na0.5TiO3)0.93(BaTiO3)0.07+ x wt% Ga2O3 ceramics significantly. At room temperature, the dielectric constant is increased and relatively low dielectric loss occurred at high frequencies. X-ray diffraction pattern showed that the coexistence of tetragonal and rhombohedral phases in the (Bi0.5Na0.5TiO3)0.93(BaTiO3)0.07 composition was not changed by adding Ga2O3

2) High efficiency Polymer Photovoltaic Devices with Glycerol-modified Buffer Layer ( IEEE Photonics Technology Letters, Vol.20, No.23, 2008, 1935)

(T.S. Huang, C.Y. Huang, Yan Kuin Su, J.S Fang, M.V. Madhava Rao, T.F. Guo, and T.C. Wen)

The properties of organic photovoltaic devices (OPVs) with poly(3,4-ethylene dioxythiophene) : poly(styrene-sulfonate) buffer layer modified by doping glycerol with different concentrations have been investigated. The power conversion efficiency(PCE) of the device has been improved from 3.37 to 4.27 % under AM 1.5 G (90 mW/cm illumination) after the buffer layer was modified. The short-circuit current density also 24% increased with the modification. Surprisingly, as the doping concentration of glycerol was more than 30 mg/ml, PCE of the OPVs no longer increased even though the conductivity of buffer layer continually increased with doping concentration of glycerol. We particularly analyzed the effect of glycerol-modified buffer layer on performance of polymer photovoltaic devices by the contact angle and atomic force microscopy measurements, and the influence of surface morphology of buffer layer was also discussed.

(M.V.Madhava Rao, Yan-Kuin Su, T.S. Huang, C.H. Yeh, and M.L. Tu)

We demonstrate that fabrication and characterization of nanocomposite polymer light emitting devices with metal Zinc Oxide(ZnO) nanoparticle and 2,3-dibutoxy-1,4-poly(phenylenevinylene) (DBPPV). The current and luminance characteristics of devices with ZnO nanoparticles are much better than those of device pure DBPPV. Optimized maximum luminance efficiencies of DB-PPV:ZnO(3:1 wt%) (1.78 cd/A) and with annealing(2.45 cd/A) having a brightness 643, 776 cd/m2 _{at a current density of 36.16, 31.67 mA/cm}2 _{are observed respectively. Current density-voltage and} brightness-voltage characteristics indicate that addition of ZnO nanoparticles can facilitate electrical injection and charge transport. The thermal annealing is thought to result in the formation of an interfacial layer between emissive polymer film and cathode. 4) Structural and electrical properties of La0.6Sr0.2Ca0.2Fe0.8M0.2O3 ( M=Al, Co, Ni, Cu, and Mn) perovskite

type oxides

(Material Science: An Indian Journal, 5, 3(2009)218) (M.V. Madhava Rao, and C.F. Kao)

Fine powders of La0.6Sr0.2Ca0.2Fe0.8M0.2O3( M=Al, Co, Ni, Cu, and Mn) were prepared by a co-precipitation method. The

structural, morphological and thermal properties of fine powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermo gravimetric analysis (TGA). The electrical conductivity of cathode materials was increasing slightly with the increasing of dopant of Al, Co, Ni, Cu and Mn. The dielectric constant of the cathodes measured as a function of frequencies, it is seen that the doping of different oxides dielectric constant increases.

5) Fullerene and pentacene as a pure organic connecting layer in tandem organic light emitting devices (J of electrochemical Society, 157, 1(2010)H69)

(M. V. Madhava Rao, Tsung-Syun Huang, Yan- Kuin Su, Yen-Tang Huang)

A nondoped organic system of fullerene _C60_/pentacene was investigated as a connecting unit for green electroluminescent tandem organic light emitting devices with two identical emissive units consisting of_N,N_-di_naphthalene-1-yl_-N,N_-diphthalbenzidine_/tris_8-hydroxyquinoline aluminum_ _Alq3_ that exhibited better current efficiencyand current density characteristics over conventional devices. At 20 mA/cm2, the current efficiency of the tandem devices using a nondoped organic layer of C60/pentacene was about 3.4 cd/A, almost 34% improvement over that of the corresponding conventional devices. The connecting unit showed a superior optical transparency, resulting in a minimal microcavity effect in thedevices. Interface dipole and band bending on both sides of the C60/pentacene interface was suggested for the formation of an intrinsic p–n junction, which is a prerequisite of a connecting unit, leading to a significant performance improvement in the tandem devices.

6) Three-Band White Light-Emitting Diodes based on Hybridization of polyfluorene and colloidal CdSe/ZnS Quantum Dots

(IEEE Photonics Technological Letters, 22,5(2010)305)

(C.Y. Huang, T.S. Huang, C.Y. Cheng, Y.C. Chen, C.T. Wan, M.V. Madhava Rao, and Yan Kuin Su)

device with the blend ratio of PFO : green QD: red QD being 6 : 1 : 1, while the maximum brightness was dramatically decreased.

7) Polymer light-emitting devices using poly(ethylene oxide) as an electron injecting layer (Nano-Micro Letters, 2,(2010)49)

(M.V. Madhava Rao, T.S. Huang, Yan-Kuin Su, M.L. Tu, C.Y. Huang, and S.S. Wu)

The performance of polymer light emitting devices (PLEDs) based on polyvinyl carbazole (PVK) is improved by introducing a nanoscale interfacial thin layer, made of poly(ethylene oxide) (PEO), between the calcium cathode and the PVK emissive layer. It is believed that the PEO layer plays a key role in enhancing the device performance. In comparison to the device with Ca/Al as the cathode, the performance of the PLED with PEO/Ca/Al cathode, including the driving voltage, luminance efficiency is significantly improved. These improvements are attributed to the introduction of a thin layer of PEO that can lower the interfacial barrier and facilitate electron injection

8) Color-tunable polymer light-emitting diodes with conjugated polymer homojunctions, (Jap. J. Appl. Phys., 49,(2010)04DK10)

(C.Y. Huang, Yan-Kuin Su, C.Y. Cheng, M.V. Madhava Rao, Y.C. Chen, T.S. Hunag, T.C. Wen, T.F. Guo)

Color-tunable light-emitting diodes with a polymer homojunction structure have been demonstrated. The homojunction structure consisted of two emissive layers, and poly(9,9-dioctylfluorene) (PFO) was used as the host material in both emissive layers. One emissive layer was composed of a blend of blue-emitting PFO and its green-emitting copolymer, and the other one was composed of a blend of green-emitting PFO copolymer and red-emitting poly[2-methoxy-5(20-ethylhexyloxy)-1,4-phenylene vinylene] (MEHPPV). In device characterization, when the injection current was increased, partial electrons could easily pass through the second emissive layer and flow into the first emissive layer near the anode, because there was no potential barrier existing in the homojunction. Therefore, the emission color of our devices could be tuned as orange, yellow, white, and cyan by adjusting the injection current or bias voltage.

9) Enhanced performance of Polymer light emitting devices using Zinc Oxide Nanoparticle with Poly(vinylcarbazole)

(J of The Electrochemical Society, 157, 8(2010)H832)

(M. V. Madhava Rao, Yan- Kuin Su, Tsung-Syun Huang, Ming-Lung Tu, Shang-Shung Wu, and Chun-Yuan Huang) The addition of zinc oxide ZnO nanoparticles into electroluminescent poly vinylcarbazole PVK polymer layers results in increased current densities, brightness, and luminance efficiencies in polymer light emitting devices. For low turn-on voltages, an increase in current density and good stability are achieved. At 9 V, we achieved a brightness of 743 cd/m2 with a luminance efficiency of 0.35 cd/A for PVK–ZnO nanocomposite devices. Electroluminescence EL spectra reveal that the EL yield of

PVK–ZnO nanoparticle devices increased greatly as compared with pure PVK devices. The current–voltage characteristics indicate that the addition of ZnO nanoparticles can facilitate better electrical injection and charge transport

10) White organic light emitting devices based on multiple-emissive-nano layers

(Nano-Micro Letters, Vol.2, No.4,(2010)242)

(M.V.Madhava Rao, Yan Kuin Su, T. S. Huang, Yi-Chun Chen)

The device has a simple structure of indium tin

oxide(ITO)/NPB(20 nm)//DPVBi(20nm)/CDBP:xIr(btp)2acac(10nm)/Alq3(25nm)/BCP(5nm)/CsF(1 nm)/Al(150 nm) x= 0.15, 2.5 and 3.0 wt%, where NPB and BCP are used as the hole-injecting layer, electron transporting and hole blocking layer, respectively. White light emission was realized in an OLED with 2.5% Ir(btp)2acac doping concentration. The device exhibits peak efficiency of 1.93 cd/A at 9V and maximum brightness of 7005 cd/m2 at 14V. The Commission Internationale de I’Eclairage(CIE)(1931) coordinates of white emission are well within the white zone, which moves from (0.35,0.33) to (0.26,0.30) when the applied voltage is varied from 5V to 14V.

二、

由計畫主持人或單位主管填寫

Please evaluate the performance of research, teaching or science and technology R&D and management Work: ( To be completed

by Project Investigator or Head of Department/Center)

(1)是否達到延攬預期目標？

Has the expected goal of recruitment been achieved?

Yes, he did a good job

(2)研究或教學或科技研發與管理的方法、專業知識及進度如何？

What are the methods, professional knowledge, and progress of the research, teaching, or R&D and management work?

During post doctoral research program, my group at NCKU in TAIWAN, He focused on An investigation and fabrication of organic light emitting devices”. Charge transport and injection properties in organic solids are of vital importance for improving performance characteristics of organic electronic devices

(3)受延攬人之研究或教學或科技研發與管理成果對該計畫(或貴單位)助益如何？

How have the research, teaching, or R&D and management results of the employed person given benefit to the project (or your unit)? His familiar with computer interfaced Keithley 2400 source meter, spectrometer(PR 650), home built probe station, thermal vacuum deposition, spin-coating, ink-jet printing, screen printing, photo-lithography, multilayer and tandem organic devices fabrication etc should be an added advantage to the proposed research

(4)受延攬人於補助期間對貴單位或國內相關學術科技領域助益如何？

How has the employed person, during his or her term of employment, benefited your unit or the relevant domestic academic field? Proposed past results in this person, work is based on a more robust and multilayer device architecture, which is especially suitable for industrial processing technique such as inkjet printing, screen printing or roll-to-roll production. The research into the electrical and optical properties of organic materials has been strongly motivated by their potential application in organic opto-electronic devices.

(5)具體工作績效或研究或教學或科技研發與管理成果：

Please describe the specific work performance, or the results of research, teaching, or R&D and management work:

His work has been presented at important international conferences and published in scientific journals, and some of his important scientific results were communicated. would like to express my strongest support.. His excellent skills, high motivation, intellectual qualities and real dedication to scientific research make him exceptionally suitable candidate for research position.

(6)

是否續聘受聘人?

_□續聘

□不續聘

Yes, In near future we will invite our research group for further research activities ※ 此報告表篇幅以三～四頁為原則。This report form should be limited to 3-4 pages in principle. ※ 此表格可上頂尖大學網頁/辦法、表格下載/綜合業務組下載。