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In this work, we report a study of the evolution of Cu–In–Ga–Se system during selenization. The metallic precursors were selenized in Se vapour atmosphere at temperature range from 210 to 380 °C. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra were used to investigate morphological and structural pro...
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Thin and ultra thin liquid films driven by a forced gas/vapor flow (stratified or annular flows), i.e. shear-driven liquid films in a narrow channel, is one of the promising candidate for the thermal management of advanced semiconductor devices with high local heat release. In experiments performed in this paper with locally heated shear-driven liq...
A thin liquid film completely covering a solid surface has the potential to rupture
into rivulets when exposed to external heat flux due to thermocapillary instabilities
and vaporization. This has implications for many industrial applications, but
particularly for fire suppression. Film rupture drastically reduces the wetted
surface area thereby ex...
Citations
... Various methods so far adopted for the preparation of copper chalcopyrite thin films include chemical bath deposition [10], selenization [11,12] sputtering [13], electrochemical deposition [14], galvanic synthesis [15], co-deposition [16], evaporation [17], electrodeposition [18,19], solvothermal method [20], MOCVD [21] and spray pyrolysis technique etc. A very few reports are available on synthesis of copper selenide by spray pyrolysis. ...
Copper selenide thin films have been deposited by spraying a mixture of aqueous solutions (0.50 M) of copper chloride hydrate (CuCl2·2H2O) and selenourea (H2NC
(Se) NH2) at various substrate temperatures. The as deposited copper selenide thin films were used to study a wide range of characteristics including structural, surface
morphological, optical, electrical, and photovoltaic power output characteristics. X-ray diffraction (XRD) study reveals that the films are polycrystalline in nature
with hexagonal (mineral klockmannite) crystal structure. The SEM study reveals that the grains are uniform with uneven spherically shaped and spread over the entire
surface of the substrates. The direct band gap values are found to be in the range 2.29-2.36 eV depending on the substrate temperature. The measured values of
efficiency (η) and fill factor (FF) are found to be 0.99 % and 0.51 respectively for film deposited at 350oC.
... In (a) and (b) of Fig. 2, there are many holes and particles in the Cu-poor films, and the grain size is less than 1 lm. With increasing Cu content in the film, the formation of Cu x Se phase during the selenization process can improve crystallinity of the film [17]. In (c) and (d) of Fig. 2, previous holes and particles disappear in the Cu-rich films, and the grain size grow larger. ...
This paper reports the Raman spectra and electrical analysis of Se-deficient Cu(In,Ga)Se2 (CIGS) films with various Cu contents. These films were deposited by low-cost two-step process consisting of sputtering of metallic precursor and subsequent selenization. Raman spectra exhibit the formation of chalcopyrite phase while signs of secondary phases like CuxSe and ordered vacancy compound are also observed. Electrical measurements show the change of main carrier source as well as the transformation of conduction type with varying Cu content. Comprehensive analysis of Raman spectra and electrical measurements qualitatively explains the relationship between electrical properties and Cu contents. Based on this relationship, the optimal range of Cu/(Ga + In) for Se-deficient CIGS solar cells is identified as 0.875–0.925, which is smaller than that for Se-sufficient CIGS solar cells due to the presence of Se vacancies. The efficiency data of CIGS solar cells fabricated with same absorber deposition process are in good agreement with this optimal range. The results of this paper could be used to estimate device performance at early process stages.
... einzelner Körner nicht möglich war, bleibt diese Zuordnung spekulativ.Während dem RTP-Prozess kommt es durch die Phasenseparation in Cu-und In-Selenide zu einer vollständigen Umstrukturierung der Schicht. Untersuchungen an teilprozessierten Absorbern zeigen für sequentiell gesputterte Cu-In[75] und Cu 0,75 Ga 0,25 -In[135] sowie für cogesputterte Cu-In Schichten[136] [137] das gleiche typische Bild: Große, hexagonale CuSe Plättchen ragen weit aus einem feinkörnigen Untergrund heraus. Der feinkörnige Untergrund besteht anfänglich aus In 4 Se 3[135], mit zunehmender Temperatur aus InSe sowie CISe[135] [137]. ...
... Untersuchungen an teilprozessierten Absorbern zeigen für sequentiell gesputterte Cu-In[75] und Cu 0,75 Ga 0,25 -In[135] sowie für cogesputterte Cu-In Schichten[136] [137] das gleiche typische Bild: Große, hexagonale CuSe Plättchen ragen weit aus einem feinkörnigen Untergrund heraus. Der feinkörnige Untergrund besteht anfänglich aus In 4 Se 3[135], mit zunehmender Temperatur aus InSe sowie CISe[135] [137]. Mit Fortschreiten der Reaktion werden die CuSe-Plättchen abgebaut. ...
... Untersuchungen an teilprozessierten Absorbern zeigen für sequentiell gesputterte Cu-In[75] und Cu 0,75 Ga 0,25 -In[135] sowie für cogesputterte Cu-In Schichten[136] [137] das gleiche typische Bild: Große, hexagonale CuSe Plättchen ragen weit aus einem feinkörnigen Untergrund heraus. Der feinkörnige Untergrund besteht anfänglich aus In 4 Se 3[135], mit zunehmender Temperatur aus InSe sowie CISe[135] [137]. Mit Fortschreiten der Reaktion werden die CuSe-Plättchen abgebaut. ...
Inhomogenitäten in industriell mit SEL-RTP (Stacked Elemental Layer- Rapid Thermal Processing) hergestellten Absorbern für Solarzellen wurden mit Rasterelektronenmikroskopie und energiedispersiver Röntgenmikroanalyse (EDX) an Oberfläche und Querschnitt untersucht. Delaminieren der Absorber macht Rückseite der Absorber und Oberseite des Rückkontaktes zugänglich. Die vertikalen Ga- und S-Gradienten wurden über EDX-Messungen mit variierter Anregungsenergie abgeschätzt.
Die Inhomogenitäten wurden drei verschiedenen Ursachen zugeordnet: Precursor, RTP oder Eindringen von Na aus dem Glassubstrat.
Inhomogenitäten im Precursor werden durch die Entnetzung des In beim Sputtern mit getrennten In- und CuGa-Targets verursacht. Dies führt zu einer lateral inhomogenen Ga/In-Verteilung nahe dem Rückkontakt. Eine raue Precursoroberfläche wird in den Absorber übertragen. Ternäre Targets verbessern die laterale Ga/In-Homogenität.
Während der RTP führen unausgeglichene Diffusionsströme von Ga und In zur Oberseite und von Leerstellen zur Unterseite zur Bildung von Poren am Rückkontakt (Kirkendall Effekt). Dies verursacht auch die Cu/Ga-reichen Rückstände, die beim Delaminieren auf dem Rückkontakt verbleiben. Vertikale Ga- und S-Gradienten werden durch RTP und Na-Gehalt im Precursor beeinflusst.
Die gravierendsten Inhomogenitäten werden durch Eindringen von Na während der RTP durch Unterbrechungen in der Na-Diffusionsbarriere zwischen Glas und Precursor verursacht. Dies können Pinholes oder Risse in der Diffusionsbarriere sein, entstanden beim Schneiden der P1-Linie mit einem ns-Laser. Die beobachteten Veränderungen in Zusammensetzung und Morphologie erweiterten den Kenntnisstand über die Wirkungsweise von Na. Na aus dem Precursor ist von Beginn der Absorberbildung an anwesend und verbessert hauptsächlich die Versorgung mit Se. Na aus dem Glas dringt erst bei höheren Temperaturen ein, wenn Se abreagiert oder verdampft ist. Dadurch verbessert es sowohl die Versorgung mit Se als auch mit S. Dies ermöglicht die bevorzugte Reaktion des Ga mit S und verändert die Ga- und S-Gradienten im Absorber massiv. Korngröße, Anzahl der Poren und der Cu/Ga-reichen Reste sowie das Ausmaß der Mo(S,Se)2-Bildung werden beeinflusst. Risse können durch die Verwendung eines ps-lasers verhindert werden.
In this work, sulfur distribution in the surface and bulk of copper indium gallium selenide (CIGS) thin films and CIGS/molybdenum (Mo) interface after sulfurization was investigated. The morphology of the surfaces and cross-sections of the thin films was observed by scanning electron microscopy. X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to study the phases, structures and chemical components of the thin films. After sulfurization, the grain size became larger and a sulfur-contained phase could be found in the XRD pattern. Interestingly, Raman spectroscopy and XPS indicated that sulfur was abundant not only in the surface but also in the CIGS/molybdenum interface. Besides, the chemical state of indium in the surface was also modified by the annealing treatment. These results help in understanding the complicated interface behavior of CIGS solar cells and benefit the improvement of the devices.
The as-deposited CuIn1-xGaxSe2 (CIGS) thin films were fabricated by magnetron sputtering from a quaternary CIGS target, and then the as-deposited films were annealed in a temperature range from 240℃ to 550℃. The effect of the annealing temperature on the electric properties (carrier concentration and carrier mobility) of the films was investigated in particular. The results show that when the annealing temperature was lower than 270℃, the highly conducive CuSe phase existed in the films leading to a high carrier concentration (1017-1019 cm-3) and a low carrier mobility (~0.1 cm2·V-1·s-1). These films are not suited for CIGS absorber usage. When the annealing temperature was higher than 410℃, the carrier mobility of the films was high about 10 cm2·V-1·s-1 and the carrier concentration was in a range of 1014-1017 cm-3 due to the disappearance of the CuSe phase. When the annealing temperature was higher than 410℃, with the increase of the annealing temperature the grains grew larger and the crystallinity of the films was enhanced, which could reduce the defects in the films and result in the decrease of the carrier concentration. From the aspect of the carrier concentration and the carrier mobility, the appropriate annealing temperature for fabricating the absorbers of the CIGS solar cells is from 450℃ to 550℃.
Thin films of copper selenide have been deposited by spraying a mixture of aqueous solutions (0.50 M) of copper chloride hydrate (CuCl2·2H2O) and selenourea [H2NC(Se)NH2] on preheated fluorine doped tin oxide coated glass substrates at various substrate temperatures. The cell configurations copper selenide/0.5 M K2SO4/C are used for studying the capacitance–voltage (C–V) characteristics in the dark, current–voltage (I–V) characteristics in dark and under illumination, photovoltaic power output and spectral response characteristics of the as deposited films. Photoelectrochemical study records that as deposited copper selenide thin films are of p-type. The spectral response characteristics of the films at room temperature show a prominent, sharp peak at 550 nm. The measured values of efficiency (η) and fill factor (FF) are found to be 0.99 % and 0.51 respectively for film deposited at 350 °C.
Thin films of copper selenide were deposited onto amorphous glass substrates at various substrate temperatures by computerized spray pyrolysis technique. The as deposited copper selenide thin films were used to study a wide range of characteristics including structural, surface morphological, optical and electrical, Hall Effect and thermo-electrical properties. X-ray diffraction study reveals that the films are polycrystalline in nature with hexagonal (mineral klockmannite) crystal structure irrespective of the substrate temperature. The crystalline size is found to be in the range of 23–28 nm. The SEM study reveals that the grains are uniform with uneven spherically shaped and spread over the entire surface of the substrates. EDAX analysis confirmed the nearly stoichiometric deposition of the film at 350 °C. The direct band gap values are found to be in the range 2.29–2.36 eV depending on the substrate temperature. The Hall Effect study reveals that the films exhibit p-type conductivity. The values of carrier concentration and mobility for the film are found to be 5.02 × 1017 cm−3 and 5.19 × 10−3 cm2 V−1 s−1; respectively for film deposited at 350 °C.
