臺灣博碩士論文加值系統

Due to the energy crisis, we rush into the solar cell research and development. Fulfillment of energy is an issue that is always covered by each of the countries, coupled with the increasing rate of world population growth the energy consumption will continue to increase. Solar cell is one of the best choices, solar cells has been studied for more than fifty years but the last decade has seen the drastic growth in the research and development in the sector and because of that, now we have so many different types of solar cells design with megawatt production capabilities. Modern solar cells design can be fabricated using different materials and can have different structure. Cu2SnSe3 (CTSe) is a potential candidate for absorber materials of solar cells.
In this study, we report the effects of doping Mg on the structural, electrical, and optical properties of these CTSe thin films for devolepment of highly efficient solar cells for long term energy production. Thin films of the CTSe and Mg-doped CTSe were sputtered with two different targets of Cu and Sn or Cu-Mg and Sn, respectively , followed by the selenization at 500-600 oC under the Se vapor. The films were characterized by FE-SEM, EDS, XRD, and Hall measurement and other analyses to explore the effects of Mg-doping with different ratios on CTSe thin film.
All the thin films CTSe and Mg-doped CTSe were deposited by DC magnetron co-sputtering at room temperature with the powers of 26 W for Cu target and 16 W for Sn target for CTSe thin films and 26 W for Cu-Mg target and 16 W for Sn target for Mg-CTSe for 1hour. A two-step selenization process was executed at 300 oC and holding period of 30 min before reaching to three different selenization temeperatures of 500 oC, 550 oC, and 600 oC. The selenization procedure had been done in Se ambient arisen from SnSe2 pellet. Almost all thin films selenized at 550 oC-selenized films had the composition closed to expected stoichiometry of Cu2SnSe3. The major XRD diffraction peaks appeared at 2θ of 26.8°, 44.8°, 53.2°, 65.5°, and 72.3° which could be attributed to (111), (220), (311), (400), and (331) planes, respectively. All the diffraction peaks of CTSe could be assigned to the crystal planes from standard structure of Cu2SnSe3 (JCPDS No.89-2879). The optical band gaps obtained by extrapolating the linear region of the absorption spectra did not significantly change. The optical absorption studies indicated a direct band gap of 1.18 ~ 1.20 eV. Undoped CTSe and Mg-0.1-CTSe films selenized at 550 oC exhibited p-type conductivity and they were n-type for Mg-0.2-CTSe and Mg-0.3-CTSe. The Hall measurements for carrier concentration and Hall mobility were 2.54×1019 cm−3 and 681 cm2V−1s−1, respectively, for undoped CTSe film, 9.08 ’ 1018 cm-3 and 71 cm2V-1s-1 for Mg-0.1-CTSe, 1.18 ’ 1019cm−3 and 11 cm2V−1s−1 for Mg-0.2-CTSe, and 1.06 ’ 1019cm−3 and 43 cm2V−1s−1 for Mg-0.3-CTSe, after selenization at 550 oC.

Abstract………………………………………………………………………………….I
Table of Contents……………………………………………………………………..III
List of Figures…………………………………………………………………………VI
List of Tables………………………………….………………………………………..XI
1. Introduction…….…………………………….…………...…………………...…….1
1.1 Research background……………………..……………………………………...1
1.2 Solar cell overview………………………………….…………………….……..2
1.3 Solar cell market………………………………………….……….….………….3
1.4 Comparison of various thin-film solar-cell types………………….……….……6
1.4.1 Thin-film silicon solar cells………………...……………….………...…7
1.4.2 CdTe (cadmium telluride thin film solar cell)……………………………….7
1.4.3 Cu(In,Ga)Se2 (copper indium gallium diselenide solar cell)……………...8
1.4.4 Cu2ZnSnSe4 (copper zinc tin diselenide solar cell)………………………….9
1.5 Research motivation and objectives…………...………………….…………….10

2. The Basic Theory and Literature Review ……………………………..…………12
2.1 The solar cell principles ………………………….…...……………………….12
2.2 Electrical characteristics ……….…………….…………………...……………13
2.2.1 The p-n junction ………….………………...…………………………………..13
2.2.2 The ideal solar cell …………………....…………………………..…………..16
2.3 CZTSe thin film solar cell basic structure ……………...……………………..19
2.4 Developtment of CTSe thin films ……………….……..……………………...20

3. Experimental Procedure ………………………………………...……..…………31
3.1 Description of experimental instruments……...………………………………..31
3.1.1 Vacuum hot press machine…………………………...……………………….31
3.1.2 DC Magnetron sputtering system……………………………………………..31
3.1.3 High-temperature vacuum furnace…………………………………………...33
3.2 Experimental materials……………...…………………………………………34
3.2.1 The solid materials……………………………………………..……………….34
3.3 Gas specification………………………………………………………………..35
3.4 Deposition parameters………………………………………………………….36
3.5 Experimental procedures……………………………………………………….38
3.5.1 SLG (soda lime glass) substrate………………………………………………39
3.5.2 Molybdenum (Mo) deposition…………………………………………………39
3.5.3 TiN deposition…………………………………………………………………...39
3.5.4 Target fabrication for the sputtering of absorber layer…………………..40
3.5.5 Deposition condition for films grown with Cu, Cu-Mg and Sn targets….40
3.5.6 Selenization………………………………………………………………………41
3.6 Characterization techniques…………………………………………………….41
3.6.1 XRD (x-ray diffractometry……………………………………………………..41
3.6.2 FE-SEM (field emission of scanning electron microscope………………..42
3.6.3 Hall effect measurement……………………………………………………….44
3.6.4 UV–vis spectrometer……………………………………………………………46
3.6.5 Raman spectroscopy……………………………………………………………48
4. Results and Discussion……………………………………………………………...51
4.1 SEM microstructure and EDS composition analysis…………………………...51
4.2 XRD analysis of the structural properties………………………………………65
4.3 Raman spectroscopy analysis…………………………………………………..71
4.4 Optical absorption analysis……………………………………………………..73
4.5 Hall measurement analysis……………………………………………………..75
5. Conclusions…………………………………………………………………………..86
References………………………………………………………………………………88

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