• Bulletin of the Korea Photovoltaic Society
• /
• v.3 no.3
• /
• pp.18-31
• /
• 2017

박막 태양전지 기술은 현재 가장 큰 시장점유율을 보이고 있는 결정질 Si 태양전지의 차세대 후보로서 큰 관심을 받고 있다. 결정질 Si 태양전지보다 높은 효율로서, 저가로 생산할 수 있는 수준을 목표로 하여 $Cu(In,Ga)Se_2$ (CIGS) 를 비롯한 다양한 종류의 박막 태양전지들이 개발되고 있는데, 이 글에서는 최근에 범용성 초저가 박막 태양전지로 각광을 받고 있는 kesterite 박막 태양전지에 대해서 살펴보기로 한다. 가장 많이 연구되는 kesterite구조의 $Cu_2ZnSn(S,Se)_4$ (CZT(S,Se)) 박막 태양전지는 차세대 태양전지의 유력 후보군인 화합물태양전지 중에서 CdTe와 CIGS 그리고 새롭게 떠오르고 있는 페로브스카이트 등에 비해 범용 무독성 원소를 광흡수층으로 사용한다는 장점을 가지고 있지만 아직까지는 이들보다 효율이 낮아 상용화하기에는 좀 더 시간이 필요할 것으로 판단된다. CZT(S,Se)계 박막 태양전지의 기본적인 물성, 공정, 분석법 등을 알아보고 고효율을 달성하는 방법에 대하여 제시하고자 한다. 공정에 대한 상세한 최근 동향과 설명은 최근 한국공업화학회 소식지에 실린 강진규 박사의 리뷰논문을 참고하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.22 no.3
• /
• pp.127-133
• /
• 2012

To achieve low-cost and high-efficiency of thin-film solar cells applications, the sol-gel method that can be coated on a large area substrate, obtain homogeneous thin films of high purity was used. We studied structural and optical characteristics versus annealing temperature of $Cu_2ZnSnS_4$ which has kesterite structure by substitution low-cost sulfur (S) instead of high-cost selenium (Se). By analyzing XRD patterns, main peak was observed at $2{\theta}=28.5^{\circ}$ when Zn/Sn ratio is 0.8/1.2. And when we observed kesterite structure which has orientation of (112) direction, the more annealing temperature increase the bigger strength of (112) direction is. $Cu_2ZnSnS_4$ thin film showed characteristics of kesterite structure at $550^{\circ}C$. And when we calculated lattice constant, a = 5.5047 and $c=11.014{\AA}$ as same JCPDS (Joint Committee on Powder Standards) data measured. We measured optical transmittance to analyze optical characteristics. Optical transmittance was lower than 65 % at visible ray (${\lambda}=380{\sim}770nm$).

• Korean Journal of Materials Research
• /
• v.22 no.5
• /
• pp.259-273
• /
• 2012

Chalcogenide-based semiconductors, such as $CuInSe_2$, $CuGaSe_2$, Cu(In,Ga)$Se_2$ (CIGS), and CdTe have attracted considerable interest as efficient materials in thin film solar cells (TFSCs). Currently, CIGS and CdTe TFSCs have demonstrated the highest power conversion efficiency (PCE) of over 11% in module production. However, commercialized CIGS and CdTe TFSCs have some limitations due to the scarcity of In, Ga, and Te and the environmental issues associated with Cd and Se. Recently, kesterite CZTS, which is one of the In- and Ga- free absorber materials, has been attracted considerable attention as a new candidate for use as an absorber material in thin film solar cells. The CZTS-based absorber material has outstanding characteristics such as band gap energy of 1.0 eV to 1.5 eV, high absorption coefficient on the order of $10^4cm^{-1}$, and high theoretical conversion efficiency of 32.2% in thin film solar cells. Despite these promising characteristics, research into CZTS-based thin film solar cells is still incomprehensive and related reports are quite few compared to those for CIGS thin film solar cells, which show high efficiency of over 20%. The recent development of kesterite-based CZTS thin film solar cells is summarized in this work. The new challenges for enhanced performance in CZTS thin films are examined and prospective issues are addressed as well.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.305-305
• /
• 2007

• Korean Journal of Materials Research
• /
• v.25 no.12
• /
• pp.708-712
• /
• 2015

This study reports the effects of $H_2S$ gas concentration on the properties of $Cu_2ZnSnS_4(CZTS)$ thin films. Specifically, sulfurization process with low $H_2S$ concentrations of 0.05% and 0.1%, along with 5% $H_2S$ gas, was studied. CZTS films were directly synthesized on Mo/Si substrates by chemical bath deposition method using copper sulfate, zinc sulfate heptahydrate, tin chloride dihydrate, and sodium thiosulfate pentahydrate. Smooth CZTS films were grown on substrates at optimized chemical bath deposition condition. The CZTS films sulfurized at low $H_2S$ concentrations of 0.05 % and 0.1% showed very rough and porous film morphology, whereas the film sulfurized at 5% $H_2S$ yielded a very smooth and dense film morphology. The CZTS films were fully crystallized in kesterite crystal form when they were sulfurized at $500^{\circ}C$ for 1 h. The kesterite CZTS film showed a reasonably good room-temperature photoluminescence spectrum that peaked in a range of 1.4 eV to 1.5 eV, consistent with the optimal bandgap for CZTS solar cell applications.

• Applied Chemistry for Engineering
• /
• v.26 no.5
• /
• pp.526-532
• /
• 2015

Solar cells with other alternative energies are being importantly recognized related with post-2020 climate change regime formation. In a point of view of materials, solar cells are classified to organic and inorganic solar cells which can provide a plant-scale electricity. In particular, recent studies about compound semiconductor solar cells, such as III-V tandem solar cells, chalcopyrite-series CIGSSe solar cells, and kesterite-series CZTSSe solar cells were rapidly accelerated. In this report, we introduce a research trend and technical issues for the compound semiconductor solar cells.

• Korean Journal of Materials Research
• /
• v.23 no.11
• /
• pp.613-619
• /
• 2013

$Cu_2ZnSn(S_x,Se_{1-x})_4$ (CZTSSe) thin films were prepared by sulfurization of evaporated precursor thin films. Precursor was prepared using evaporation method at room temperature. The sulfurization was carried out in a graphite box with S powder at different temperatures. The temperatures were varied in a four step process from $520^{\circ}C$ to $580^{\circ}C$. The effects of the sulfurization temperature on the micro-structural, morphological, and compositional properties of the CZTSSe thin films were investigated using X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The XRD and Raman results showed that the sulfurized thin films had a single kesterite crystal CZTSSe. From the FE-SEM and TEM results, the $Mo(S_x,Se_{1-x})_2$ (MoSSe) interfacial layers of the sulfurized CZTS thin films were observed and their thickness was seen to increase with increasing sulfurization temperature. The microstructures of the CZTSSe thin films were strongly related to the sulfurization temperatures. The voids in the CZTSSe thin films increased with the increasing sulfurization temperature.

• Current Photovoltaic Research
• /
• v.4 no.3
• /
• pp.114-118
• /
• 2016

$Cu_{1.8}Zn_{1.2}(Sn_{1-x}Ge_x)S_4$ (CZTGeS) nanocrystals were mechanochemically synthesized from elemental precursor powders without using any organic solvents and any additives. The composition of CZTGeS nanocrystals were systematically varied with different Ge mole fraction (x) from 0.1 to 0.9. The XRD, Raman spectroscopy, high-resolution TEM, and diffuse reflectance studies show that the as-synthesized CZTGeS nanocrystals exhibited consistent changes in various structural and optical properties as a function of x, such as lattice parameters, wave numbers for $A_1$ Raman vibration mode, interplanar distances (d-spacing), and optical bandgap energies. The bandgap energy of the synthesized CZTGeS nanocrystals gradually increases from 1.40 to 1.61 eV with increasing x from 0.1 to 0.9, demonstrating that Ge-doping is useful means to tune the bandgap of mechanochemically synthesized nanocrystals-based kesterite thin-film solar cells. The preliminary solar cell performance is presented with an efficiency of 3.66%.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2012.05a
• /
• pp.98.2-98.2
• /
• 2012

Thin film solar cells are growing up in the market due to their high efficiency and low cost. Especially CdTe and $CuInGaSe_2$ based solar cells are leading the other cells, but due to the limited percentage of the elements present in our earth's crust like Tellurium, Indium and Gallium, the price of the solar cells will increase rapidly. Copper Zinc Tin Sulfide (CZTS) and Copper Zinc Tin Selenide (CZTSe) semiconductor (having a kesterite crystal structure) are getting attention for its solar cell application as the absorber layer. CZTS and CZTSe have almost the same crystal structure with more environmentally friendly elements. Various authors have reported growth and characterization of CZTSe films and solar cells with efficiencies about 3.2% to 8.9%. In this study, a novel method to prepare CZTSe has been proposed based on selenization of stacked Copper Selenide ($Cu_2Se$), Tin Selenide ($SnSe_2$) and Zinc Selenide (Zinc Selenide) in six possible stacking combinations. Depositions were carried out through RF magnetron sputtering. Selenization of all the samples was performed in Close Space Sublimation (CSS) in vacuum at different temperatures for three minutes. Characterization of each sample has been performed in Field Emission SEM, XRD, Raman spectroscopy, EDS and Auger. In this study, the properties and results of $Cu_2ZnSnSe_4$ thin films grown by selenization will be presented.

• Current Photovoltaic Research
• /
• v.3 no.3
• /
• pp.97-100
• /
• 2015

The kesterite $Cu_2ZnSnSe_4$ (CZTSe) thin film solar cells were synthesized by selenization of sputtered Cu/Sn/Zn metallic precursors on Mo coated soda lime glass substrate in Ar atmosphere. Cu/Sn/Zn metallic precursors were deposited by DC magnetron sputtering process with 30 W power at room temperature. As-deposited metallic precursors were placed in a graphite box with Se pellets and selenized using rapid thermal processing furnace at various temperature ($480^{\circ}C{\sim}560^{\circ}C$) without using a toxic $H_2Se$ gas. Effects of Selenization temperature on the morphological, crystallinity, electrical properties and cell efficiency were investigated by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD), J-V measurement system and solar simulator. Further details about effects of selenization temperature on CZTSe thin films will be discussed.