• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.210-213
• /
• 2006

나노입자를 이용하여 치밀한 $Cu(In,\;Ga)Se_2$ 태양전지용 광흡수층을 제조하기 위해 먼저, 콜로이달 방법으로 합성된 20nm이하의 CIGS 나노입자를 저가의 스프레이 법을 이용하여 CIGS 막을 제조하였다. 제조된 CIGS막을 two-zone RTP (rapid temperature Process) 방법으로 Se 분위기 안에서 열처리를 행하였다. 입자의 치밀화를 위해 기판의 온도, Se 증발온도와 수송가스의 유량을 조절하여 CIGS 입자성장을 행하였다. 그러나, Se의 증발온도가 높을수록 CIGS와 MO 박막 사이에서 $MoSe_2$ 층이 형성되었다. 형성된 $MoSe_2$층의 부피 팽창으로 인해 하부의 유리기판과 Mo층 사이에서 peeling off 현상이 발생했다. 이러한 Peeling off현상을 억제하면서 CIGS 나노입자 성장을 하기 위해, Se 공급을 빨리 할 수 있도록 Se의 증기압을 높였으며, 최적조건에서 급속 열처리 공정을 통해 CIGS 나노입자 성장과 치밀화를 위한 소결거동을 관찰하였다.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.25 no.4
• /
• pp.402-406
• /
• 1988

The MgGa2Se4 single crystal for study of optical properties is for the first time grown by Bridgmna method. The crystal structure of grown MgGa2Se4 single crystal has the Rhomobohedral structure (R3m) and its lattice constant are a=3.950\ulcorner c=38.893\ulcornerin Hexagonal structure. The energy band structure of grown MgGa2Se4 single crystal structure has direct band gap and the optical energy gap measured from optical absorption in this crystal is 2.20eV at 290K. The temperature dependence of energy gap was given Eg(T)=Eg(O)-aT\ulcorner)B+T), from varshni equation, where Eg(O)=2.34eV, a=8.79x10**-4eV/and b=250K.

• Korean Journal of Materials Research
• /
• v.20 no.12
• /
• pp.661-668
• /
• 2010

Cu(In,Ga)$Se_2$(CIGS) photovoltaic thin films were electrodeposited on Mo/glass substrates with an aqueous solution containing 2 mM $CuCl_2$, 8 mM $InCl_3$, 20 mM $GaCl_3$ and 8mM $H_2SeO_3$ at the electrodeposition potential of -0.6 to -1.0 V(SCE) and pH of 1.8. The best chemical composition of $Cu_{1.05}In_{0.8}Ga_{0.13}Se_2$ was found to be achieved at -0.7 V(SCE). The precursor Cu-In-Ga-Se films were annealed for crystallization to chalcopyrite structure at temperatures of 100-$500^{\circ}C$ under Ar gas atmosphere. The chemical compositions, microstructures, surface morphologies, and crystallographic structures of the annealed films were analyzed by EPMA, FE-SEM, AFM, and XRD, respectively. The precursor Cu-In-Ga-Se grains were grown sparsely on the Mo-back contact and also had very rough surfaces. However, after annealing treatment beginning at $200^{\circ}C$, the empty spaces between grains were removed and the grains showed well developed columnar shapes with smooth surfaces. The precursor Cu-In-Ga-Se films were also annealed at the temperature of $500^{\circ}C$ for 60 min under Se gas atmosphere to suppress the Se volatilization. The Se amount on the CIGS film after selenization annealing increased above the Se amount of the electrodeposited state and the $MoSe_2$ phase occurred, resulting from the diffusion of Se through the CIGS film and interaction with Mo back electrode. However, the selenization-annealed films showed higher crystallinity values than did the films annealed under Ar atmosphere with a chemical composition closer to that of the electrodeposited state.

• Journal of the Korean Vacuum Society
• /
• v.21 no.6
• /
• pp.322-327
• /
• 2012

The strain effects of ZnSe epilayer on ZnSe/GaAs heterojunction structure grown by molecular beam epitaxy have been investigated by using electroreflectance (ER) spectroscopy. The ER measurements were performed as a function of modulation voltage, dc bias voltage, and temperature. From the room temperature ER spectrum, we observed a heavy-hole (HH: 2.609 eV) and light-hole (LH: 2.628 eV) transitions due to a compressive strain. With increasing the bias voltage, the amplitude of HH transition signal decreased and the amplitude of LH transition signal was almost the same. From the temperature dependence of ER spectra, we have studied the interaction between the strain and the thermal expansion coefficient.

• Journal of Sensor Science and Technology
• /
• v.10 no.6
• /
• pp.328-337
• /
• 2001

The stochiometric mix of evaporating materials for the $CdGa_2Se_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdGa_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $630^{\circ}C$ and $420^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CdGa_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.27{\times}10^{17}cm^{-3}$, $345\;cm^2/V{\cdot}s$ at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuInSe_2$ single crystal thin film, we have found that the values of spin orbit splitting ${\Delta}So$ and the crystal field splitting ${\Delta}Cr$ were 106.5 meV and 418.9 meV at 10 K, respectively. From the photoluminescence measurement on $CdGa_2Se_4$ single crystal thin film, we observed free excition ($E_x$) existing only high quality crystal and neutral bound exiciton ($D^{\circ}$, X) having very strong peak intensity. Then, the full-width-at -half-maximum(FWHM) and binding energy of neutral donor bound excition were 8 meV and 13.7 meV, respectivity. By Haynes rule, an activation energy of impurity was 137 meV.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.47.2-47.2
• /
• 2011

광전환 효율 20% (AM1.5G) 이상의 고효율 화합물 박막태양전지의 광흡수층으로 많은 관심을 받고 있는 $Cu(In,Ga)Se_2$ (CIGS) 태양전지의 광흡수층은 다양한 공정에 의해 제조가 가능하다. 현재 고효율 CIGS 셀 생성을 위해 널리 사용되고 있는 CIGS 흡수층 성장공정은 "co-evaporation (동시증발법)"과 2-step 공정이라 불리는 "precursorselenization(전구체-셀렌화)" 방법이다. 동시증발법은 개별원소 Cu, In, Ga, Se들을 고진공 분위기에서 고온(550~600$^{\circ}C$) 기판위에 증착하는 방법으로 소면적에서 가장 좋은 효율(~20%)을 보이는 공정이다. 하지만, 고온, 고진공 공정조건과 대면적 증착시 온도 및 조성 불균일 등의 문제점 등으로 상용화에 어려움이 있다. 전구체-셀렌화 공정은 1단계에서 다양한 방식(예: 스퍼터링, 전기도금, 프린팅 등) 방식으로 CuGaIn 전구체를 증착하고, 2단계에서 고온(550~600$^{\circ}C$)하에 H2Se gas 혹은 Se vapor와 반응시켜 CIGS를 생성한다. 일본의 Showa Shell와 Honda Soltec 등에 의해 이미 상업화 되었듯이, 저비용 대면적으로 상업화 가능성이 높은 공정으로 평가되고 있다. 하지만, 2단계에서 사용되는 H2Se 및 Se vapor의 유독성, 기상 Se과 금속전구체 간의 느린 셀렌화 반응속도, 셀렌화반응 후 생성된 CIGS 박막 두께방향으로의 Ga 불균일 분포, 생성된 CIGS/Mo 계면 접착력 저하 등의 문제점들이 개선, 해결되어야만 상업화에 성공할 수 있을 것이다. 본 연구에서는 Se layer가 코팅된 금속전구체의 셀렌화 반응메카니즘을 in-situ high-temperature XRD를 이용하여 연구하였다. 금속전구체는 스퍼터링, 스프레이 등 다양한 방법으로 제조되었고, 반응메카니즘 연구결과를 바탕으로 Se 코팅된 금속전구체를 이용한 급속열처리 공정의 최적화를 시도하였다.

• Applied Microscopy
• /
• v.25 no.2
• /
• pp.65-72
• /
• 1995

The interfacial structures of ZnSe/GaAs which were grown by single chamber MBE at $300^{\circ}C$ were investigated by high resolution transmission electron microscope working at 300 kV with resolution of 0.18 nm. The interfaces of ZnSe/GaAs whose thickness is 2,700 nm are wavy and extensive stacking faults were formed in ZnSe epilayer but the interfaces maintained the coherency with the substrate GaAs. The stacking faults are formed in {111} planes and their sizes are $10{\sim}20nm$ in length and two or three atomic layer in width with the density of $10^9/cm^2$. Micortwins and moire fringes are also observed. However. in 10 nm ZnSe epilayer, the interfaces are pseudomorphic and only moire fringes are observed in local areas. The cylindrical defects which are perpendicular to the interface with $50{\sim}60nm$ in length, were observed with the interval of 50 nm at ZnSe/GaAs interfaces in 2,700nm epilayer. The origin and character of these defects are unknown, however, they played a role of producing the structural defects at the interfaces.

• Solar Energy
• /
• v.20 no.2
• /
• pp.43-54
• /
• 2000

We prepared and characterized $Cu(In_{1-x}Ga_x)Se_2$(CIGS) films using a elemental co-evaporation method for absorbing layer of high efficiency thin film solar cells. The CIGS films deposited on a soda-lime glass exhibited low resistivity because of higher carrier concentration. Na was accumulated at the CIGS surface and the 0 and Se were also accumulated at the surface, suggesting that oxidation is a driving force of Na accumulation. The structure of CIGS film was modified or a secondary phase was formed in the Cu-poor CIGS bulk films probably due to the incorporation of Na into Cu vacancy sites. As the Ga/(In+Ga) ratio increased, the diffraction peaks of $Cu(In_{1-x}Ga_x)Se_2$ films were shifted to larger angle and splitted, and the grain size of $Cu_{0.91}(In_{1-x}Ga_x)Se_2$ films became smaller. All $Cu_{0.91}(In_{1-x}Ga_x)Se_2$ films showed the p-type conductivity regardless of the Ga/(In+Ga) ratio. Ag/n-ZnO/i-ZnO/CdS/$Cu_{0.91}(In_{0.7}Ga_{0.3})Se_2$/Mo solar cells were fabricated. The currently best efficiency in this study was 14.48% for $0.18cm^2$ area ($V_{oc}=581.5mV,\;J_{sc}=34.88mA$, F.F=0.714).

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1584-1586
• /
• 2002

CuIn$Se_2$ (CIS) and related compounds such as Cu($In_xGa_{1-x})Se_2$(CIGS) have been studied by their potential for use in photovoltaic devices. CIS thin film materials which have high absorption coefficient and wide bandgap, have attracted much attention as an alternative to crystalline and amorphous silicon solar cells currently in use. Cu-rich CIGS film have very low resistivity, due to coexistence of the semimetallic $Cu_{2-x}Se$. In-rich CIGS films show high resistivity, since these films are compensated films without the $Cu_{2-x}Se$ phase. Optical properties of the CIGS films also change in accordance with the resistivity for the Cu/(In+Ga) ratio. The Cu-rich films have different spectra from In-rich films in near infrared wavelengths.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11b
• /
• pp.163-166
• /
• 2001

The stochiometric mix of evaporating materials for the $ZnGa_{2}Se_{4}$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $ZnGa_{2}Se_{4}$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $610^{\circ}C$ and $450^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $ZnGa_{2}Se_{4}$ single crystal trun films measured from Hall effect by van der Pauw method are $9.63{\times}10^{17}cm^{-3}$, $296cm^{2}/V{\cdot}s$ at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c axis of the $ZnGa_{2}Se_{4}$ single crystal thin film, we have found that the values of spin orbit splitting $\Delta$ So and the crystal field splitting $\Delta$Cr were 251.9 meV and 183.2 meV at 10 K, respectively. From the photoluminescence measurement on $ZnGa_{2}Se_{4}$ single crystal thin film, we observed free excition (Ex) existing only high quality crystal and neutral bound exiciton $(A^{0},X)$ having very strong peak intensity. Then, the full-width-at -half-maximum(FWHM) and binding energy of neutral acceptor bound excition were 11 meV and 24.4 meV, respectivity. By Haynes rule, an activation energy of impurity was 122 meV.