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By evaporating single element to grow two kinds of stacked layer precursors In/Cu/Se and In/Se/Cu first, In/Cu/Se precursor forms as CuSe2, CuSe and In metal phase, but In/Se/Cu precursor forms mainly as Cu11In9 alloy, In metal phase and amorphous Se. In RTA selenization process, the two kinds of stacked layer precursors form to CuInSe2 (for short as CIS) thin film in different reaction mechanisms, but both of the two stacked layers form to CIS with rough surface and uncompact structure, not the ideal thin film. Replacing by co-evaporating two elements to grow two kinds of binary stacked layrer precursors InSe/CuSe/Se and InSe/Cu/InSe/Se, finds that, after the RTA selenization process, both of the two precursors form CIS with good smoothness and compactness, and InSe/CuSe/Se precursor with much better structure than the other, having mean grain size in about 1~3£gm. In this result, appears that if skipping the stage which single element reacts with Se, generating the selenide InxSey, CuxSey (Such as InSe, In2Se3, CuSe, Cu2Se et cetera.), and using In-Se, Cu-Se binary stacked precursors in RTA process directly can acquire better CIS structure. And then, growing InSe/CuSe/Se stacked layer on Mo metal back contact, finds the phenomenon that the formed CIS thin film has many circle bulges structure on Mo thin film. After investigating this case, the reason was considered as the remaining compressive stress of Mo thin film (-272.9MPa). The interface problem of Mo/CIS has been solved by tuning the remaining stress of Mo with 1£gm thickness to compressive stress -194MPa, and 1£gm thickness CIS thin film is grown on that. However, if the remaining stress continuingly drecrese to almost no stress 1MPa or tensile stress 709.9MPa, CIS thin film peels with Mo thin film from the substrate. In the end, analyzing the CIS thin film formed by InSe/CuSe/Se stacked layer precursor (Cu/In ratio is 24%/26%), the result shows that the CIS film is a P-type In-rich thin film, the sheet resistence is 6.8*106£[/ ¡¼, carrier mobility is 1.103*102 cm2/V-s, carrier density is 1.318*1018 cm-3, and energy gap is about 1.0eV, the absorption coefficient is above 6.5*104cm-1, and the composition all over the film is very close to each other¡Aappearing this film with nice composition homogenization.

Low-cost and high-efficiency are of continuous interest for the fabrication of solar cells. I-III-VI compound semiconductors Cu(In,Ga)Se2 (CIGS) are the most important absorber materials in developing thin film solar cells. The bandgap of CIGS varies from about 1.1 to 1.7 eV, which is within the maximum solar absorption region. This is very important for the optimum conversion efficiency. The extraordinarily high absorption coefficient from direct bandgap leads to thinner thickness and lower fabrication cost for its use in thin film solar cells. In this experiment, we deposit CuInGa alloy layer on Mo-coated soda-lime glass by RF sputtering and then use selenization process to form Cu(In,Ga)Se2. We study the characterization of sputtered CIG alloy layer and selenized CIGS thin film.

Making CZTSe thin film of sputtering and Selenization.Sputtering Zn¡BSn precursor layers on Soda-lime glass¡Aand using evaporating to stack Cu layer.Let it annearing under Selenium atmosphere for less then one hour. We are looking forward a profit annealing process to grow CZTSe thin film.By changing temperature of Substrate¡Bannealing time and heating rate of Substrate. Using XRD and Raman to analysis composition and crystal structure. The morphology from SEM images.Taking analysis on optical and electronic property of the thin film.

In this experiment, selenides are used as the precursor and CIGS thin films are synthesized through selenization. At the first stage, the precursor with the layers of In-Se/Ga-Se/Cu-Se failed to produce CIGS thin films when the temperature is going up 10¢J per minute to the target temperature during selenization and the change of the composition of the precursor, the temperature duration and the temperature of selenization is tried. Later, the reaction is successfully done when the layers are changed into In-Ga-Se/Cu-Se with the temperature going up 10¢J per minute to 550¢J, lasting for 5 minutes. With various Ga containments, I analyize the optical and electronic properties. In order to see the composition of CIGS thin films in different propotion of Cu/In+Ga and Ga/In+Ga, I use EPMA and the properties of XRD peak shift with the containment of Ga to estimate the proportion of the containment of Ga. I found the conclusions by EPMA and XRD are very similar. At 150¢J, the precursors Cu-Se, In-Se and Ga-Se are fabricated and XPS, Raman, XRD or else are used to speculate the bonding of them. In addition, using XRD and Raman to analyze In-Ga-Se/Cu-Se selenides, I found, between 150¢J and 300¢J, Cu2-xSe bonding is the main; at 350¢J, InSe bonding intensifies obviously; at 400¢J, CIGS is formed.

This experiment was growing CZTSe (Cu2ZnSnSe4) single phase thin film by using rapid thermal selenization process on Se/Cu/Sn/Zn/SLG thin film. It can complete the reaction to avoid Cu2SnSe3 appearing during the RTP. To discuss the effect of nitrogen and selenium flow rates on the thin film quality and adhesion, and to confirm the composition of the CZTSe single phase thin film. And I also annealed and changed the Se/Cu/Zn/Sn/SLG stacked layer to improve the thin film uniformity. Finally, it was stacked on the Mo/SLG and annealed by varying raising rate of temperature in order to enhance the adhesion. The results indicated that the various flow of nitrogen could cause different conditions. The element selenium easily escaped due to lower nitrogen flow could not provide enough outer pressure; larger nitrogen flow carried the extra high vapor pressure gas go through the surface of substrate and lead to the worse adhesion with the substrate. Unfortunately, using the analysis of X-ray diffraction and Raman spectrum couldn¡¦t determine the single phase of CZTSe. However, it has been confirmed by optical bandgap. In this experiment, the compositions of CZTSe single phase are found to be Cu-poor and Zn-poor, the optical bandgap (Eg) is 0.88~1.04 eV, and the resistivity (£l) is 1~10-2 £[-cm. By the rapid thermal selenization process, because of the rapid gradient of temperature, it brought out the diffused non-uniformly among the precursors. Therefore, the uniformity of thin films would not be perfect. As the result, re-annealing and change are the efficient methods to improve the uniformity of the thin film. The problems are un-wetting effect exists in the stacked liquid phase Se/Cu/Zn/Sn and the sodium glass substrates. The morphologies of the thin films are island connection. Finally, increasing the temperature in 15 oC per second and annealing the thin film for one minute at 250 oC with the stacked layer of Se/Cu/Sn/Zn/Mo/SLG are successful to promote the adhesion between the CZTSe and Mo.

Since the phase stability region of CuInSe2 (CIS) extends as wide as a few atomic percent, composition variation in a microscopic scale is nature to this material and can be detected by EPMA or TEM-EDS. As the detection volume is kept as small as possible (e.g. we used an electron probe with a diameter of 3nm to measure a TEM specimen thinned by a focused ion beam to a 80 nm thickness), the composition data fluctuate rather significantly. For a near-stoichiometric CIS film prepared by co-evaporation or a selenized film using binary selenides as precursor, the composition variations in a nanometer scale were quite distinct. Due to the tedious procedures for making TEM specimens and doing measurements, we normally used EPMA for the composition analysis. Although the composition was measured in a micrometer scale, its variation still can be detected and expressed by the standard deviation. Our results showed that the selenized films prepared by using binary selenides as precursors (they were used to make the device in this work) had much better composition uniformity as compared with the films selenized from the elemental precursors. We also found that even the time period for the selenization process was short (rapid thermal selenization) or long (conventional selenization), the composition variation did not make any changes. Since there still has problems for making devices by using rapid thermal selenization, we successfully fabricated the CIS thin-film solar cells through the conventional selenization processes. The I-V characteristics of the best CIS cell is in the following: Voc=0.398 V, Jsc=41.14 mA/cm2, fill factor (FF)=54.58%, efficiency= 9.29%. We also made a CIGS cell and found that the open circuit voltage was increased to 0.461 V. However, the efficiency was 4.42%. It still needs more effort to boost its short circuit current and fill factor.

Copper Indium Gallium DiSelenide absorber layers are fabricated using a two step manufacturing-friendly process. The first step involves the sequential deposition of Copper and Gallium and codeposition of Indium and Selenium, not necessarily in that order, at 275o C. This is followed by the second stage, where the substrate is annealed in the presence of Selenium and a thin layer of Copper is deposited to neutralize the excess Indium and Gallium on the surface to form the Copper Indium Gallium diSelenide absorber layer. Elimination of the need for high degree of control and elimination of toxic gases like hydrogen selenide aid in the easy scalability of this process to industry. The performance of CuInGaSe2/CdS/ZnO solar cells thus fabricated was characterized using techniques such as I-V, C-V, Spectral Response and EDS/SEM. Cells with open circuit voltages of 450-475 mV, short circuit current densities of 30-40 mA/cm², fill factors of 60-68% and efficiencies of 8-12% were routinely fabricated. Gallium in small amounts seems to improve the open circuit voltages by 50-100 mV without significantly affecting the short circuit currents and the band gap in Type I precursors. Gallium also improves the adhesion of the CIS layer to the molybdenum back contact. Efforts are also being aimed at improving the short circuit current densities in our high bandgap devices. It is believed that improperly bonded Ga is hurting the electronic properties of the CIGS films. A part of this work involves the reduction of the detrimental effect of Ga on the Jsc's by modifying the base process, so as to improve the homogeneity of the film. The modifications include lowering the Ga level as well as fine-tuning the annealing step. Ar annealing of the samples has also been incorporated. The short circuit current densities have been improved significantly by the above mentioned modifications. At present, the best Jsc's are in the 33-35 mA/cm² range. The Voc's have also been improved by splitting the Ga into two layers and replacing the top Cu layer by a Ga layer. Light soaking studies of the absorber have also been carried out. The baseline Type I process has also been adapted to a new load-locked in-line evaporator system. Device performance dependence on Ga and In thickness as well as the top selenization temperature has been determined in this research. The effect of moisture on the quality of the films has been studied. Bandgap variations due to the presence/absence of Se during the Cu deposition has been investigated. The impact of substrate cleaning/Moly deposition conditions on the device performance has been explored. Insitu Ar annealing studies of CIGS absorbers have been carried out. Alternate buffer layers have been pursued. Devices with Voc's as high as 480 mV, Jsc's as high as 40.7 mA/cm² and fill factors of 66% have been fabricated.

Following the concept utilize binary selenides as precursors with rapid thermal process (RTP) to fabricate CuInSe2 (CIS) thin film. In order to find the most promise process to get high quality CIS, several precursor stacking sequences have been tested which including SLG/In-Se/Cu-Se/Se, SLG/Cu-Se/In-Se/Se, SLG/0.1In-Se/Cu-Se/0.9/In-Se/Se, and SLG/0.5In-Se/Cu-Se/0.5/In-Se/Se, and the experiment result shows SLG/In-Se/Cu-Se/Se is the most suitable stacking sequence. Subsequently, varying Se flux to obtain several kinds copper selenides (Cu7Se4, Cu3Se2, CuSe, CuSe2) and indium selenides, try to find the suitable pairs through these binary selenides in SLG/In-Se/Cu-Se/Se structure. The suitable combination phase in Cu-Se precursor layer is CuSe blend with CuSe2. Large grain size CIS, about 1£gm, can be prepared in such precursor phase with film thickness between 700nm to 1£gm, strong (112) prefer-orientation vertical with substrate as well as good adhesion. Films were characterized through scanning election microscopy (SEM) to obtain grain size, surface morphology as well as film thickness. The X-ray diffractometer (XRD) was used to identify phase contained in whole film, and the phase constitution near surface layer was examined by Raman spectroscopy. If there are some second phases remaining in the thin film, combining the phase examination result of XRD and Raman spectroscopy, it can be estimate the second phase exist in the surface layers or internal film area.