• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.111-115
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• 2015

To improve the efficiency of the Si solar cell, high minority carrier life time is required. Therefore, the passivation technology is important to eliminate point defects on the silicon surface, causing the loss of minority carrier recombination. PECVD or post-annealing of thermally-grown $SiO_2$ is commonly used to form the passivation layer, but a high-temperature process and low thermal stability is a critical factor of low minority carrier lifetime. In this study, atomic layer deposition was used to grow the $Al_2O_3$ passivation layer at low temperature process. $Al_2O_3$ was selected as a passivation layer which has a low surface recombination velocity because of the fixed charge density. For the high charge density, an improved minority carrier lifetime, and a low surface recombination, nitrogen was doped in the $Al_2O_3$ thin film and the improvement of passivation was studied.

• Current Photovoltaic Research
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• v.6 no.2
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• pp.43-48
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• 2018

The traditional silicon heterojunction solar cells consist of intrinsic amorphous silicon to prevent recombination of the silicon surface and doped amorphous silicon to transport the photo-generated electrons and holes to the electrode. Back contact solar cells with silicon heterojunction exhibit very high open-circuit voltages, but the complexity of the process due to form the emitter and base at the backside must be addressed. In order to solve this problem, the structure, manufacturing method, and new materials enabling the carrier selective contact (CSC) solar cell capable of achieving high efficiency without using a complicated structure have recently been actively developed. CSC solar cells minimize carrier recombination on metal contacts and effectively transfer charge. The CSC structure allows very low levels of recombination current (eg, Jo < 9fA/cm2), thereby achieves high open-circuit voltage and high efficiency. This paper summarizes the core technology of CSC solar cell, which has been spotlighted as the next generation technology, and is aiming to speed up the research and development in this field.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.541-543
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• 1995

We propose the improved threshold current ratio method to determine the reflectivity of coated facets. The carrier recombination time used in the improved threshold current ratio method depends on the value of facet reflectivities. However, the carrier recombination time used in the conventional threshold current ratio method is constant regardless of facet reflectivities. The difference between the results of the two methods increases as the reflectivity of a coated facet decreases.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.4
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• pp.408-413
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• 1995

We investigated the effect of mechanical backside damage upon minority carrier recombination lifetime measurement in Czochralski silicon substrate by laser excitation/microwave reflection photoconductance decay method. The intensity of mechanical damage was evaluated by X-ray double crystal rocking curve, X-ray section topography and wet oxidation/preferential etch methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the threshold full width at half maximum value which affect minority carrier lifetime measurement is about 13 secs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.27-34
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• 1999

We investigated the effect of mechanical back side damage in viewpoint of electrical and surface morphological characteristics in Czochralski silicon wafer. The intensity of mechanical damage was evaluated by minority carrier recombination lifetime by laser excitation/microwave reflection photoconductance decay technique, atomic force microscope, optical microscope, wet oxidation/preferential etching methods. The data indicate that the higher the mechanical damage degree, the lower the minority carrier lifetime, and surface roughness, damage depth and density of oxidation induced stacking fault increased proportionally.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.10
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• pp.1427-1435
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• 2002

The main aim of the present article is numerically to investigate the micro-scale heat transfer phenomena in a silicon microstructure irradiated by picosecond-to-femtosecond ultra-short laser pulses. Carrier-lattice non-equilibrium phenomena are simulated with a self-consistent numerical model based on Boltzmann transport theory to obtain the spatial and temporal evolutions of the lattice temperature, the carrier number density and its temperature. Especially, an equilibration time, after which carrier and lattice are in equilibrium, is newly introduced to quantify the time duration of non-equilibrium state. Significant increase in carrier temperature is observed for a few picosecond pulse laser, while the lattice temperature rise is relatively small with decreasing laser pulse width. It is also found that the laser fluence significantly affects the N 3 decaying rate of Auger recombination, the carrier temperature exhibits two peaks as a function of time due to Auger heating as well as direct laser heating of the carriers, and finally both laser fluence and pulse width play an important role in controlling the duration time of non-equilibrium between carrier and lattice.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.230.1-230.1
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• 2016

본 연구에서는 Host-Dopant system 기반 적색 인광 OLED의 Emitting layer(EML)에서 doping 위치에 따른 특성 변화를 분석하였다. EML은 host 물질로 60 nm 두께의 CBP를 사용하고, 적색 발광을 위해 10 %의 $Ir(btp)_2$를 CBP의 Front, Middle, Back side에 각각 20 nm씩 doping하였다. 본 구조의 적색 인광 OLED는 current density, luminance, efficiency, EL spectrum 등을 통해 전기적, 광학적 특성 변화를 확인하였다. Front, Back side에 doping으로 인한 CBP의 Energy level이 3.6 eV에서 1.9 eV로 감소하여 각각 HTL/EML, EML/HBL의 경계에 carrier direct injection이 활성화 되었고, 이로 인한 charge balance의 저하를 확인하였다. EL spectrum결과 각 소자는 CBP의 618 nm 파장 외에도, 추가적으로 TPBi의 398 nm, NPB의 456 nm의 파장을 보였다. 이를 통해 doping 위치에 따라 exciton이 형성되는 recombination zone이 이동하고 있음을 확인하였고, Front side는 6 V의 인가전압에서는 발광 파장이 398 nm에서 높은 값을 보이나 8 V, 10 V, 12 V에서 618 nm에서 높은 값을 보이는 것으로 인가전압에 의해 recombination zone이 HTL쪽으로 이동되는 것 또한 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.947-950
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• 2001

We report the characteristics of organic light emitting diodes (OLEDS) by controlling the carrier mobility according to the crystalline of Iron(II) Phthalocyanine(Fe-Pc) and metal-free Phthalocyanine (H$_2$-Pc). In order to change the recombination zone, we controlled the hole mobility by changing the crystal structures of Fe-Pc and H$_2$-Pc. OLEDs were constructed with ITO/Fe-Pc/triphenyl-diamine (TPD)/tris-(8-hydroxyquinoline)aluminum (Alq$_3$)/Al and ITO/H$_2$-Pc/triphenyl-diamine (TPD)/tris-(8-hydroxyquinoline)aluminum (Alq$_3$)/Al. The electroluminescent properties were changed according to the heat-treatments of Fe-Pc and H$_2$-Pc. We observed that the recombination zone and the carrier mobility were changed as the higher occupied molecular orbital levels of Fe-Pc and H$_2$-Pc decreased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.85-88
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• 2006

The transport properties of amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. The effects of As addition on the carrier mobility and recombination lifetime in amorphous selenium (a-Se) films have been studied using the moving photocarrier grating (MPG) technique. We have found an increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with the drift mobilities of holes and electrons obtained by time of flight (TOF) measurement.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.250-254
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• 2007

Applying the moving photo-carrier grating(MPG) technique and time-of-flight(TOF) measurements, we studied the transport properties of stabilized amorphous selenium typical of the material used in direct conversion X-ray imaging devices. For MPG measurement, we obtained electron and hole mobility and the recombination lifetime of $\alpha-Se$ films with arsenic(As) additions. We found an apparent increase in hole drift mobility and recombination lifetime, especially when 0.3 % As was added into $\alpha-Se$ film, whereas electron mobility decreased with the addition of As due to the defect density. For TOF measurement, a laser beam with pulse duration of 5 ns and wavelength of 350 nm was illuminated on the surface of $\alpha-Se$ with a thickness of 400 ${\mu}m$. The measured hole and electron transit times were about 8.73 ${\mu}s$ and 229.17 ${\mu}s$, respectively.