원자전달 라디칼 중합(ATRP)에 의해 poly(vinyl chloride) (PVC) 주사슬과 poly(styrene sulfonic acid) (PSSA) 곁사슬로 되어있는 양쪽성 PVC-g-PSSA 가지형 공중합체를 합성하였다. PVC-g-PSSA 가지형 공중합체 고분자를 템플레이트로 사용하고 졸겔법을 적용하여, 결정성 아타네제상의 미세기공 이산화티타튬 필름을 제조하였다. TiO2 전구체인 TTIP를 친수성인 PSSA 영역과 선택적으로 작용시켜 TiO2 메조기공 필름을 성장하였으며, 이를 주사전자 현미경 (SEM)과 엑스레이회절 (XRD)분석을 통해 분석하였다. 스핀코팅 횟수와 P25 도입에 따른 염료감응 태양전지 성능을 체계적으로 분석하였다. 그 결과 준고체 고분자 전해질을 이용하였을 때, 100 mW/㎠ 조건에서 에너지 변환 효율이 2.7%에 이르렀다.

To reduce manufacturing costs of crystalline silicon solar cells, silicon wafers have become thinner. In relation to this, the properties of the aluminium-back surface field (Al-BSF) are considered an important factor in solar cell performance. Generally, screen-printing and a rapid thermal process (RTP) are utilized together to form the Al-BSF. This study evaluates Al-BSF formation on a (111) textured back surface compared with a (100) flat back surface with variation of ramp up rates from 18 to 89˚C/s for the RTP annealing conditions. To make different back surface morphologies, one side texturing using a silicon nitride film and double side texturing were carried out. After aluminium screen-printing, Al-BSF formed according to the RTP annealing conditions. A metal etching process in hydrochloric acid solution was carried out to assess the quality of Al-BSF. Saturation currents were calculated by using quasi-steady-state photoconductance. The surface morphologies observed by scanning electron microscopy and a non-contacting optical profiler. Also, sheet resistances and bulk carrier concentration were measured by a 4-point probe and hall measurement system. From the results, a faster ramp up during Al-BSF formation yielded better quality than a slower ramp up process due to temperature uniformity of silicon and the aluminium surface. Also, in the Al-BSF formation process, the (111) textured back surface is significantly affected by the ramp up rates compared with the (100) flat back surface.

We have investigated the structural and electrical properties of Ga-doped ZnO (GZO) thin films deposited by anRF magnetron sputtering at various RF powers from 50 to 90W. All the GZO thin films are grown as a hexagonal wurtzitephase with highly c-axis preferred parameters. The structural and electrical properties are strongly related to the RF power. Thegrain size increases as the RF power increases since the columnar growth of GZO thin film is enhanced at an elevated RFpower. This result means that the crystallinity of GZO is improved as the RF power increases. The resistivity of GZO rapidlydecreases as the RF power increases up to 70W and saturates to 90W. In contrast, the electron concentration of GZO increasesas the RF power increases up to 70W and saturates to 90W. GZO thin film shows the lowest resistivity of 2.2×10−4Ωcmand the highest electron concentration of 1.7×1021cm−3 at 90W. The mobility of GZO increases as the RF power increasessince the grain boundary scattering decreases due to the reduced density of the grain boundary at a high RF power. Thetransmittance of GZO thin films in the visible range is above 90%. GZO is a feasible transparent electrode for application asa transparent electrode for thin film solar cells.

We have investigated the structural and optical properties of Ga-doped ZnO (GZO) thin films deposited by RFmagnetron sputtering at various deposition temperatures from 100 to 500oC. All the GZO thin films are grown as a hexagonalwurtzite phase with highly c-axis preferred parameter. The structural and electrical properties are strongly related to depositiontemperature. The grain size increases with the increasing deposition temperature up to 400oC and then decreases at 500oC. Thedependence of grain size on the deposition temperature results from the variation of thermal activation energy. The resistivityof GZO thin film decreases with the increasing deposition temperature up to 300oC and then decreases up to 500oC. GZO thinfilm shows the lowest resistivity of 4.3×10−4Ωcm and highest electron concentration of 1.0×1021cm−3 at 300oC. The mobilityof GZO thin films increases with the increasing deposition temperature up to 400oC and then decreases at 500oC. GZO thinfilm shows the highest resistivity of 14.1cm2/Vs. The transmittance of GZO thin films in the visible range is above 87% atall the deposition temperatures. GZO is a feasible transparent electrode for the application to the transparent electrode of thinfilm solar cells.

Silicon heterojunction solar cells have been studied by many research groups. In this work, silicon heterojunction solar cells having a simple structure of Ag/ZnO:Al/n type a-Si:H/p type c-Si/Al were fabricated. Samples were fabricated to investigate the effect of transparent conductive oxide growth conditions on the interface between ZnO:Al layer and a-Si:H layer. One sample was deposited by ZnO:Al at low working pressure. The other sample was deposited by ZnO:Al at alternating high working pressure and low working pressure. Electrical properties and chemical properties were investigated by light I-V characteristics and AES method, respectively. The light I-V characteristics showed better efficiency on sample deposited by ZnO:Al by alternating high working pressure and low working pressure. Atomic concentrations and relative oxidation states of Si, O, and Zn were analyzed by AES method. For poor efficiency samples, Si was diffused into ZnO:Al layer and O was diffused at the interface of ZnO:Al and Si. Differentiated O KLL spectra, Zn LMM spectra, and Si KLL spectra were used for interface reaction and oxidation state. According to AES spectra, sample deposited by high working pressure was effective at reducing the interface reaction and the Si diffusion. Consequently, the efficiency was improved by suppressing the SiOx formation at the interface.

Cu(In,Ga)Se2(CIGS) photovoltaic thin films were electrodeposited on Mo/glass substrates with an aqueous solution containing 2 mM CuCl2, 8 mM InCl3, 20 mM GaCl3 and 8mM H2SeO3 at the electrodeposition potential of -0.6 to -1.0 V(SCE) and pH of 1.8. The best chemical composition of Cu1.05In0.8Ga0.13Se2 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˚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˚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˚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 MoSe2 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.

In this paper, double texturization of multi crystalline silicon solar cells was studied with laser and reactive ion etching (RIE). In the case of multi crystalline silicon wafers, chemical etching has problems in producing a uniform surface texture. Thus various etching methods such as laser and dry texturization have been studied for multi crystalline silicon wafers. In this study, laser texturization with an Nd:YVO4 green laser was performed first to get the proper hole spacing and 300μm was found to be the most proper value. Laser texturization on crystalline silicon wafers was followed by damage removal in acid solution and RIE to achieve double texturization. This study showed that double texturization on multi crystalline silicon wafers with laser firing and RIE resulted in lower reflectance, higher quantum yield and better efficiency than that process without RIE. However, RIE formed sharp structures on the silicon wafer surfaces, which resulted in 0.8% decrease of fill factor at solar cell characterization. While chemical etching makes it difficult to obtain a uniform surface texture for multi crystalline silicon solar cells, the process of double texturization with laser and RIE yields a uniform surface structure, diminished reflectance, and improved efficiency. This finding lays the foundation for the study of low-cost, high efficiency multi crystalline silicon solar cells.

The hybrid structured photo-electrode for dye-sensitized solar cells was fabricated based on the composites of nanoparticles and nanowires. Three samples with different hybrid structures were prepared with 17 vol%, 43 vol%, and 100 vol% nanowires. The energy conversion efficiency was enhanced from 5.54% for pure nanoparticle cells to 6.01% for the hybrid structure with 17 vol% nanowires. For the hybrid structured layers with high nanowires concentration (43 vol% and 100 vol%), the efficiency decreased with the nanowire concentration, because of the decrease of specific surface area, and of thus decreased current density. The random orientations of nanowires can be preserved by the doctor blade process, resulted in the enhanced efficiency. The hybrid structured layer can possess the advantages of the high surface area of nanoparticles and the rapid electron transport rate and the light scattering effect of nanowires.

We have studied methods to save Si source during the fabrication process of crystalline Si solar cells. One way is to use a thin silicon wafer substrate. As the thickness of the wafers is reduced, mechanical fractures of the substrate increase with the mechanical handling of the thin wafers. It is expected that the mechanical fractures lead to a dropping of yield in the solar cell process. In this study, the mechanical properties of 220-micrometer-solar grade Cz p-type monocrystalline Si wafers were investigated by varying saw-damage etching conditions in order to improve the flexural strength of ultra-thin monocrystalline Si solar cells. Potassium hydroxide (KOH) solution and tetramethyl ammonium hydroxide (TMAH) solution were used as etching solutions. Etching processes were operated with a varying of the ratio of KOH and TMAH solutions in different temperature conditions. After saw-damage etching, wafers were cleaned with a modified RCA cleaning method for ten minutes. Each sample was divided into 42 pieces using an automatic dicing saw machine. The surface morphologies were investigated by scanning electron microscopy and 3D optical microscopy. The thickness distribution was measured by micrometer. The strength distribution was measured with a 4-point-bending tester. As a result, TMAH solution at 90˚C showed the best performance for flexural strength.

Changes in surface morphology and roughness of dc sputtered ZnO:Al/Ag back reflectors by varying the deposition temperature and their influence on the performance of flexible silicon thin film solar cells were systematically investigated. By increasing the deposition temperature from 25˚C to 500˚C, the grain size of Ag thin films increased from 100 nm to 1000 nm and the grain size distribution became irregular, which resulted in an increment of surface roughness from 6.6 nm to 46.6 nm. Even after the 100 nm thick ZnO:Al film deposition, the surface morphology and roughness of the ZnO:Al/Ag double structured back reflectors were the same as those of the Ag layers, meaning that the ZnO:Al films were deposited conformally on the Ag films without unnecessary changes in the surfacefeatures. The diffused reflectance of the back reflectors improved significantly with the increasing grain size and surface roughness of the Ag films, and in particular, an enhanced diffused reflectance in the long wavelength over 800 nm was observed in the Ag back reflectors deposited at 500˚C, which had an irregular grain size distribution of 200-1000 nm and large surface roughness. The improved light scattering properties on the rough ZnO:Al/Ag back reflector surfaces led to an increase of light trapping in the solar cells, and this resulted in a noticeable improvement in the Jsc values from 9.94 mA/cm2 for the flat Ag back reflector at 25˚C to 13.36 mA/cm2 for the rough one at 500˚C. A conversion efficiency of 7.60% (Voc = 0.93, Jsc = 13.36 mA/cm2, FF = 61%) was achieved in the flexible silicon thin film solar cells at this moment.

To fabricate TiO2 nanoparticle-based dye sensitized solar cells (DSSCs) at a low-temperature, DSSCs were fabricated using hydropolymer and ZnO nanoparticles composites for the electron transport layer around a low-temperature (200˚C). ZnO nanoparticle with 20 nm and 60 nm diameter were used and Pt was deposited as a counter electrode on ITO/glass using an RF magnetron sputtering. We investigate the effect of ZnO nanoparticle concentration in hydropolymer and ZnO nanoparticle solution on the photoconversion performance of the low temperature fabricated (200˚C) DSSCs. Using cis-bis(isothiocyanato)bis(2,20 bipyridy1-4,40 dicarboxylato) ruthenium (II) bis-tetrabutylammonium (N719) dye as a sensitizer, the corresponding device performance and photo-physical characteristics are investigated through conventional physical characterization techniques. The effect of thickness of the ZnO photoelectrode and the morphology of the ZnO nanoparticles with the variations of hydropolymer to ZnO ratio on the photoconversion performance are also investigated. The morphology of the ZnO layer after sintering was examined using a field emission scanning electron microscope (FE-SEM). 60 nm ZnO nanoparticle DSSCs showed an incident photon-to-current conversion efficiency (IPCE) value of about 7% higher than that of 20 nm ZnO nanoparticle DSSCs. The maximum parameters of the short circuit current density (Jsc), the open circuit potential (Voc), fill factor (ff), and efficiency (η) in the 60 nm ZnO nanoparticle-based DSSC devices were 4.93 mA/cm2, 0.56V, 0.40, and 1.12%, respectively.

스크린 인쇄공법을 이용하여 구형 실리콘 태양전지용 전면 전극을 제작하였고 그 물성을 검토하였다.집광형 구형 실리콘 태양전지는 종래의 결정질 실리콘 태양전지 발전 시스템 설치비용 중 21%를 차지하는 실리콘 소재의 사용량을 줄이기 위해 볼 형태의 구형 실리콘을 사용하였고, 입사되는 태양광을 최대한 활용하기위해 알루미늄으로 된 집광판을 사용하는 것을 특징으로 한다. 전도성 필러로써 Flake 형태의 Ag 파우더를 사용하였고, 기재와의 접착력을 부여하기 위한 유기 바인더로서 에폭시수지, 폴리에스테르수지,아크릴수지 등을 비교 검토한 결과, 에폭시수지 고형분 12%를 첨가한 paste가 기재와의 접착성, 태양전지 광전변환효율, 내구성에서 가장 우수함을 알 수 있었다.

Mo thin films were used for the back electrode because of the low resistivity in the Mo/CuInGaSe2 contact inchalcopyrite solar cells. 1µm thick Mo thin films were deposited on soda lime glass by varying the Ar pressure with the dc-magnetron sputtering process. The effects of the Ar pressure on the morphology of the Mo back electrode were studied andthe relationships between the morphology and electro-optical properties, namely, the resistivity as well as the reflectance of theMo thin films, were investigated. The resitivity increased from 24µΩ·cm to 11833µΩ·cm; this was caused by the increasedsurface defect and low crystallinity as the Ar pressure increased from 3×10−3 to 3×10−2Torr. The surface morphologies ofthe Mo thin films changed from somewhat coarse fibrous structures to irregular and fine celled strucutures with increased surfacecracks along the cell boundaries, as the Ar pressure increased from 3×10−3 to 3×10−2Torr. The changes of reflectances in thevisible light range with Ar pressures were mainly attributed to the surface morphological changes of the Mo thin films. Thereflectance in the visible light range showed the highest value of 45% at 3×10−3Torr and decreased to 18.5% at 3×10−2Torr.

This paper investigates the dependence of a-Si:H/c-Si passivation and heterojunction solar cell performances on various cleaning processes of silicon wafers. It is observed that the passivation quality of a-Si:H thin-films on c-Si wafers depends highly on the initial H-termination properties of the wafer surface. The effective minority carrier lifetime (MCLT) of highly H-terminated wafer is beneficial for obtaining high quality passivation of a-Si:H/c-Si. The wafers passivated by p(n)-doped a-Si:H layers have low MCLT regardless of the initial H-termination quality. On the other hand, the MCLT of wafers incorporating intrinsic (i) a-Si:H as a passivation layer shows sensitive variation with initial cleaning and H-termination schemes. By applying the improved cleaning processes, we can obtain an MCLT of 100μsec after H-termination and above 600μsec after i a-Si:H thin film deposition. By adapting improved cleaning processes and by improving passivation and doped layers, we can fabricate a-Si:H/c-Si heterojunction solar cells with an active area conversion efficiency of 18.42%, which cells have an open circuit voltage of 0.670V, short circuit current of 37.31 mA/cm2 and fill factor of 0.7374. These cells show more than 20% pseudo efficiency measured by Suns-Voc with an elimination of series resistance.

염료감응형 태양전지에 사용되기 위한 유기/무기 복합소재를 합성하였다. 다양한 분자량(600, 1,500, 2,000, 3,400)의 polyethylene glycol 양 끝단을 ethoxysilane기로 치환하여 전구체를 제조하였으며, 전구체간의 졸-겔 반응을 통하여 복합소재를 합성하였다. 전해질막은 유기/무기 복합소재를 KI 및 I2로 도핑하여 제조하였으며, 제조한 전해질의 이온전도도 특성을 측정하였다. 전해질막의 이온전도도는 원료로 사용한 PEG에 크게 영향을 받았으며 가장 높은 이온전도도는 분자량 2,000의 PEG를 사용한 전해질막에서 볼 수 있었다. 복합전해질막은 이온전도도에 있어서 큰 향상을 보였다. PEO 전해질막에 비하여 분자량 2,000의 PEG를 사용하여 제조한 복합전해질막은 월등하게 높은 이온전도도를 보였다.

염료감응형 태양전지를 위한 고분자 전해질막을 제조하였다. 고분자물질로는 Poly(ethylene oxide) (PEO)를 사용하였으며, 가소제로서 poly(ethylene glycol) (PEG)를 첨가하였고, 전해질염 및 I - /I3 - ,의 공급원으로서 KI 및 I2를 첨가하여 고분자 전해질막을 제조하였으며, 이와 같은 고분자 전해질막을 바탕으로 염료감응형 태양전지를 제조하였다. 고분자 전해질 내의 가소제로서의 PEG 함량은 0%에서 85%의 범위로 변화하였다. 이러한 PEG 함량 전 구간에서 고분자 전해질막은 그 형태를 자체적으로 유지하는(self supporting) 완벽한 고체 전해질막의 형태로 제조되었다. PEG 함량이 증가하면서 전해질막을 통한 이온전도도와 I3- 이온의 확산도계수는 증가하였다. 염료감응형 태양전지에 있어서는 고분자 전해질막 내의 PEG 함량이 증가하면서 그 효율이 증가함을 볼 수 있었다.

CuInSe2 (CIS) thin films were electrodeposited on Mo-coated glass substrates in acidic solutionscontaining Cu2+, In3+, and Se4+ ions, depending on deposition parameters such as deposition potential (-0.4 to-0.8V[SCE]) and pH (1.7 to 1.9). The influences of PH and deposition potential on the atomic composition ofCu, In, and Se in the deposited films were observed. The best chemical composition, approaching 1:1:2 atomicratio for the elements, was achieved at -0.5V (SCE) and pH 1.8. The as-deposited films showed low crystallinityand were annealed at 300 to 500oC for 30 min to improve crystallization. The surface morphologies,microstructures, and crystallographic structures of the annealed films as well as the as-deposited films wereanalyzed with AFM, SEM, and XRD. The defects of spherical particles appeared on the surfaces of CIS thinfilms in the as-deposited state and decreased in size and number with increasing annealing temperatures.Additionally, the crystallization to chalcopyrite structure and surface roughness (Ra) of the as-deposited thinfilms were improved with the annealing process.

Electrochemical deposition characteristics of CdSe nanorods were investigated for hybrid solar cell applications. CdSe nanorods were fabricated by electrochemical method in CdSO4 and H2SeO3 dissolved aqueous solution using an anodic aluminum oxide (AAO) template. Uniformity of CdSe nanorods was dependent on the diameter and the height of holes in AAO. The current density, current mode, bath composition and temperature were controlled to obtain a 1:1 atomic composition of CdSe. CdSe nanorods deposited by direct-current method showed better uniformity compared to those deposited by purse-current and/or purse-reverse current methods due to the bottom-up filling characteristics. H2SeO3 concentration showed more significant effects on pH of solution and stoichiometry of deposits compared to that of CdSO4. A 1:1 stoichiometry of uniform CdSe nanorods was obtained from 0.25M CdSO4-5 mM H2SeO3 electrolytes with a direct current of 10 mA/cm2 at room temperature. X-ray diffraction and electron diffraction pattern investigations demonstrate that CdSe nanorods are a uniform cubic CdSe crystal.