Correlation of doping concentration, charge transport of host, and lifetime of thermally activated delayed fluorescent devices

Song, Wook,Lee, Woochul,Kim, Kong Kyeom,Lee, Jun Yeob Elsevier 2016 ORGANIC ELECTRONICS Vol.37 No.-

<P><B>Abstract</B></P> <P>Origin of doping concentration dependence of lifetime of thermally activated delayed fluorescent (TADF) devices was examined using a TADF emitter doped in a hole transport type and a bipolar host material. Lifetime of the hole transport type host based TADF device was increased according to doping concentration of TADF emitter, while that of the bipolar host based TADF device was decreased according to doping concentration of TADF emitter. The doping concentration dependence of the lifetime could be correlated with recombination zone of the emitting layer. Broad recombination zone at high doping concentration in the hole transport type host and at low doping concentration in the bipolar host was proposed as the main contributor of the doping concentration dependence of the lifetime.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lifetime increase in thermally activated delayed fluorescent devices with a unipolar host according to doping concentration. </LI> <LI> Constant lifetime in thermally activated delayed fluorescent device with a bipolar host according to doping concentration. </LI> <LI> Correlation of recombination zone broadening with lifetime of thermally activated delayed fluorescent devices. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nb를 도핑하여 제작한 p형 WS2의 도핑농도에 따른 구조적 특성 연구

박기천,서민기,최보규,이경백,신동희 한국물리학회 2023 새물리 Vol.73 No.1

Herein, we demonstrated the doping of single-layer WS2 with Nb using chemical vapor deposition. The doping concentration of Nb atoms was adjusted by varying the amount of NbCl5 powder from 60 mg to 75 mg. On the basis of the doping concentration-dependent variations in Raman frequencies, photoluminescence, work function, and structural, and electrical measurements, the p-type characteristics of WS2 were strengthened with the increasing doping concentration. As estimated from the photoluminescence of Nb-doped WS2, the photoluminescence peak was 627 nm (1.98 eV) in pristine WS2 but red-shifted by 85 nm to 712 nm (1.74 eV) in the sample doped with 75 mg of Nb. This result suggested that Nb is a good p-type doping impurity for WS2. 화학 기상 증착법에 의해 Nb가 도핑된 WS2 결정립을 제작하였다. 여기서, Nb 원자의 도핑농도는 NbCl5의 파우더의 양을 60 mg에서 75 mg까지 변화시켜 조절하였다. 도핑농도에 따른 WS2의 특성을 구조적 및 전기적 실험을 통해 분석한 결과, 도핑농도가 증가함에 따라 WS2의 p형 특성이 더욱 강해진다는 것을 라만 주파수, 광발광, 및 일함수의 변화로 확인하였다. 특히, 광발광 측정을 통해 도핑농도의 증가에 따라 에너지 띠를 자세히 측정한 결과,초기 상태 WS2 광발광 피크는 627 nm (1.98 eV)이였지만, 75 mg Nb가 도핑된 시료에서는 712 nm (1.74 eV)로 85 nm 이동하였다. 이 결과 Nb가 WS2의 p형 도핑 불순물로서 매우 우수하다는 것을 시사한다.

Improved photoelectrochemical performance of molybdenum (Mo)-doped monoclinic bismuth vanadate with increasing donor concentration

Tayebi, Meysam,Tayyebi, Ahmad,Lee, Byeong-Kyu Elsevier Science Publishers 2019 Catalysis today Vol.328 No.-

<P><B>Abstract</B></P> <P>Molybdenum (Mo)-doped Monoclinic Bismuth Vanadate (Mo-BiVO<SUB>4</SUB>; BVO) catalysts were fabricated via a simple dip coating method. We systematically studied the effect of Mo-doping with various concentration (1–5%) in BVO electrode through photoelectrochemical (PEC), Mott-Schottky and impedance measurement. Intermediate heat treatment and number of successive dip coating deposition were utilized to control the monoclinic crystallization and thickness of Mo-BVO photoanodes. Furthermore, the effect of Mo-doping in morphology, structure, chemical states and optical properties of the obtained electrodes were characterized by different physico-chemical and morphological methods BVO with 2% Mo doping (2% Mo-BVO) showed the best PEC performance, of about 15 times higher than that of the pure BVO. Improved charge carrier transport and optimized light absorption obtained upon Mo doping into the BVO crystal lattice while the monoclinic scheelite structure with small band-gap was retained. To understand the effect of Mo-doping, Mott Schottky and Impedance measurement carried out, in order to evaluate the donor concentration and conductivity of pure BVO and Mo-BVO. Interestingly, 2% Mo-BVO showed the maximum donor concentration (5.7E + 27) and minimum flat band potential (V<SUB>fb</SUB> = −0.45) compared to other prepared electrodes. Furthermore, we attempt to discuss the improved PEC performance of Mo-BVO using high donor concentration, up-shifting of Fermi level and consequently facilitating electrons transport in Mo-BVO compared to pure BVO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mo-BVO electrodes were fabricated via a four dip-coating cycles method. </LI> <LI> Photocurrent density increased 15-fold for 2% Mo-BVO compared with pure BVO. </LI> <LI> Mott-Schottky results indicated 2% Mo-BVO has the maximum donor concentration. </LI> <LI> The PEC measurement showed shifting of onset potential to lower voltage for Mo-BVO. </LI> <LI> The Impedance data exhibited 2% Mo-BVO has the best PEC performance compared to other photoanodes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Characteristics of Polycrystalline β-SiC Films Deposited by LPCVD with Different Doping Concentration

Sangsoo Noh,Eungahn Lee,Xiaoan Fu,Chen Li,Mehran Mehregany 한국전기전자재료학회 2005 Transactions on Electrical and Electronic Material Vol.6 No.6

The physical and electrical properties of polycrystalline β-SiC were studied according to different nitrogen doping concentration. Nitrogen-doped SiC films were deposited by LPCVD(low pressure chemical vapor deposition) at 900 ºC and 2 torr using 100 % H2SiCl2 (35 sccm) and 5 % C2H2 in H2(180 sccm) as the Si and C precursors, and 1 % NH3 in H2(20~100 sccm) as the dopant source gas. The resistivity of SiC films decreased from 1.466 Ω×㎝ with NH3 of 20 sccm to 0.0358 Ω×㎝ with 100 sccm. The surface roughness and crystalline structure of β-SiC did not depend upon the dopant concentration. The average surface roughness for each sample 19-21 ㎚ and the average surface grain size is 165 ㎚. The peaks of SiC(111), SiC(220), SiC(311) and SiC(222) appeared in polycrystalline β-SiC films deposited on Si/SiO2 substrate in XRD(X-ray diffraction) analysis. Resistance of nitrogen-doped SiC films decreased with increasing temperature. The variation of resistance ratio is much bigger in low doping, but the linearity of temperature dependent resistance variation is better in high doping. In case of SiC films deposited with 20 sccm and 100 sccm of 1 % NH3, the average of TCR(temperature coefficient of resistance) is -3456.1 ppm/°C and -1171.5 ppm/°C, respectively.

RF Sputtering으로 증착한 어닐링 온도변화에 따른 Ga-doped ZnO 박막 특성 연구

한승익,김홍배 한국반도체디스플레이기술학회 2016 반도체디스플레이기술학회지 Vol.15 No.2

This paper, Ga-doped ZnO (GZO) thin films which were deposited on Corning glass substrate using an magnetron sputtering deposition technology and then the post deposition annealing process was conducted for 30 minutes at different temperature of 100, 200, 300, and 400℃, respectively. So as to investigate the properties for the relevant the Concentration and Oxygen Vacancy with Annealing temperature of Ga-doped ZnO thin films by RF Sputtering method. The Carrier concentration is enhanced as annealing temperature decreases, and also the oxygen vacancy concentration is enhanced as annealing temperature decreased. Oxygen vacancy will decrease along with Carrier concentration. This change in Carrier concentration is related to changes in oxygen vacancy concentration. The figure of merit obtained in this study means that Ga-doped ZnO films which annealed at 400℃ have the lowest Carrier concentration and Oxygen vacancy, which have the highest optoelectrical performance that it could be used as a transparent electrode.

Characteristics of Polycrystalline β-SiC Films Deposited by LPCVD with Different Doping Concentration

Noh, Sang-Soo,Lee, Eung-Ahn,Fu, Xiaoan,Li, Chen,Mehregany, Mehran The Korean Institute of Electrical and Electronic 2005 Transactions on Electrical and Electronic Material Vol.6 No.6

The physical and electrical properties of polycrystalline $\beta$-SiC were studied according to different nitrogen doping concentration. Nitrogen-doped SiC films were deposited by LPCVD(1ow pressure chemical vapor deposition) at $900^{\circ}C$ and 2 torr using $100\%\;H_2SiCl_2$ (35 sccm) and $5 \%\;C_2H_2$ in $H_2$(180 sccm) as the Si and C precursors, and $1\%\;NH_3$ in $H_2$(20-100 sccm) as the dopant source gas. The resistivity of SiC films decreased from $1.466{\Omega}{\cdot}cm$ with $NH_3$ of 20 sccm to $0.0358{\Omega}{\cdot}cm$ with 100 sccm. The surface roughness and crystalline structure of $\beta$-SiC did not depend upon the dopant concentration. The average surface roughness for each sample 19-21 nm and the average surface grain size is 165 nm. The peaks of SiC(111), SiC(220), SiC(311) and SiC(222) appeared in polycrystalline $\beta$-SiC films deposited on $Si/SiO_2$ substrate in XRD(X-ray diffraction) analysis. Resistance of nitrogen-doped SiC films decreased with increasing temperature. The variation of resistance ratio is much bigger in low doping, but the linearity of temperature dependent resistance variation is better in high doping. In case of SiC films deposited with 20 sccm and 100 sccm of $1\%\;NH_3$, the average of TCR(temperature coefficient of resistance) is -3456.1 ppm/$^{\circ}C$ and -1171.5 ppm/$^{\circ}C$, respectively.

Impact of fin shapes and channel doping concentrations on the operation of junctionless transistors

Park, So Jeong,Jeon, Dae-Young,Kim, Gyu-Tae Elsevier 2019 MICROELECTRONIC ENGINEERING Vol.207 No.-

<P><B>Abstract</B></P> <P>The influence of variations in the Si fin shape on the electrical properties of junctionless transistors (JLTs) was investigated through two-dimensional Poisson equation numerical simulations at different doping concentrations. Stronger gate coupling in a triangular fin channel was observed, arising from suppression of the variation in the conduction threshold voltage with increasing doping concentration, compared to JLTs with rectangular fin channels. The potential distribution in the channel cross-section shows a less varied potential at the bottom of a triangular channel than at the bottom of a rectangular channel, and supports the result that triangular channels are less sensitive to variations in channel doping concentration.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The performance of junctionless transistors (JLT) was investigated with fin shapes. </LI> <LI> The impact of fin shapes was studied with numerical simulations. </LI> <LI> V<SUB>th</SUB> variation with doping concentration N<SUB>d</SUB> is suppressed in triangular channels. </LI> <LI> Heavily doped JLTs are more vulnerable with change of fin shapes. </LI> <LI> Stronger gate coupling in triangular fin is observed with potential distributions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

p-Pillar 영역의 두께와 농도에 따른 4H-SiC 기반 Superjunction Accumulation MOSFET 소자 구조의 최적화

정영석,구상모,Jeong, Young-Seok,Koo, Sang-Mo 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.6

In this work, static characteristics of 4H-SiC SJ-ACCUFETs were obtained by adjusting the p-pillar region. The structure of this SJ-ACCUFET was designed by using a two-dimensional simulator. The static characteristics of SJ-ACCUFET, such as the breakdown voltages, on-resistance, and figure of merits, were obtained by varying the p-pillar doping concentration from $1{\times}10^{15}cm^{-3}$ to $5{\times}10^{16}cm^{-3}$ and the thickness from $0{\mu}m$ to $9{\mu}m$. The doping concentration and the thickness of p-pillar region are closely related to the break down voltage and on-resistance and threshold voltages. Hence a silicon carbide SJ-ACCUFET structure with highly intensified breakdown voltages and low on-resistances with good figure of merits can be achieved by optimizing the p-pillar thickness and doping concentration.

PC1D 시뮬레이션을 이용해 태양전지 효율 최적화를 위한 주요 인자 연구

이기원(Lee, Kiwon),이종환(Lee, Jonghwan),이준신(Yi, Junsin) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.11

결정질 실리콘 웨이퍼를 이용한 고효율 태양전지를 제작하기 위해서는 반드시 고려해야 할 주요 인자들이 있다. 그 중에서도 Base resistivity, Thickness, Doping concentration, Texture size, Texture angle등의 주요 인자를 PC1D 시뮬레이션 프로그램을 이용하여 최적화 해 보았다. 그 결과, Base resistivity값은 낮을수록 좋으나 지나치게 낮을 경우 재결합으로 인해 효율이 떨어지기 때문에 Base resistivity = 1{Omega}{cdot}cm에서 최대 효율을 얻을 수 있었다. 또한, Thickness는 두꺼울수록 R={rho}(L/A)의 식에 의해 직렬저항이 증가하여 효율이 감소하므로 Thickness = 200{mu}m 정도가 적정 값임을 확인할 수 있었다. Doping concentration의 경우 높을수록 재결합으로 인해 효율이 떨어지며 Doping concentration = 3.69{times}10^{-20}cm^{-3}에서 가장 좋은 효율을 보였다. Textrure size와 Textrure angle은 그 값이 클수록 빛의 흡수 정도가 증가해 효율이 증가함을 볼 수 있었고 Textrure size = 2{sim}4{mu}m, Texture angle = 79?에서 높은 효율을 보여주었다. 이와 같은 조건에서 고효율 태양전지를 제작을 위한 시뮬레이션을 한 결과, 16.23%의 변환효율을 얻을 수 있었다.

안티몬 도핑된 주석 산화물 투명전도막의 몰 농도에 따른 치밀한 표면 구조 제조

배주원,구본율,안효진,Bae, Ju-Won,Koo, Bon-Ryul,Ahn, Hyo-Jin 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.1

Sb-doped $SnO_2$ (ATO) transparent conducting films are fabricated using horizontal ultrasonic spray pyrolysis deposition (HUSPD) to form uniform and compact film structures with homogeneously supplied precursor solution. To optimize the molar concentration and transparent conducting performance of the ATO films using HUSPD, we use precursor solutions of 0.15, 0.20, 0.25, and 0.30 M. As the molar concentration increases, the resultant ATO films exhibit more compact surface structures because of the larger crystallite sizes and higher ATO crystallinity because of the greater thickness from the accelerated growth of ATO. Thus, the ATO films prepared at 0.25 M have the best transparent conducting performance ($12.60{\pm}0.21{\Omega}/{\square}$ sheet resistance and 80.83% optical transmittance) and the highest figure-of-merit value ($9.44{\pm}0.17{\times}10^{-3}{\Omega}^{-1}$). The improvement in transparent conducting performance is attributed to the enhanced carrier concentration by the improved ATO crystallinity and Hall mobility with the compact surface structure and preferred (211) orientation, ascribed to the accelerated growth of ATO at the optimized molar concentration. Therefore, ATO films fabricated using HUSPD are transparent conducting film candidates for optoelectronic devices.