呈万噺氏5

1 (論文博士(英文))Date of submission (month day, year): July 9,2018

Department

Mechanical En ineerin
AppliC抑t's name

MitsukiNakashima

Con捻Ctfaculw

Masanobulzaki

Abstract (Doctor)
Title ofThesis

Study on Fabrication and characterization of chalcogenide・based Thin Film

Photovoltaic Devices ofEnvironmental Harmony TypeApprox.80o words、

Recently, the many researches on rene、Nable energy are carrying out to solve theenvironmental problems such as the depletion of加Ssil fuels and the global、¥arming. EspeciaⅡy,

the techn010gies of energy conversion using solar energy are spreading 、Nidely. solar ce11S areelectronic devices 、刃hich converts solar energy direcdy into electrical energy through thePhotovoltaic e行'ect. NOW, many research organizations are researching the cU2ZnsnS4‑based

Solar ce11S as the chalcogenide‑based thin film solar ce11S of the environmental harmony type、Nhich are composed of eadh・abundant materials 、¥ith no rare elements,10、V・cost and nontoxic.
However, the safe fabrication methods 、vhich obt毎n the hi晉h conversion e伍Ciency of thePractical use level have not been established. Therefore, it is very important to investigate theCharacteristics ofthese solar ce11S fabricated by several methods 、vith a safe process. This study
has been performed from the above standpoint
This thesis presents the investigation of the characteristics of the cU2Znsnse4 and cU2SnS3
4︑thin films and solar ce11S fabricated by our proposed method such as vacuum evaporation,

Sulfurization and annealing methods.
First, the cU2Znsnse4 thin films and solar ce11S 、刃ere fabricated by the ne、N vacuum
evaPⅨ'ation method which used only the deposition stage using the cU2Znsnse4 Compound as
the starting evaporation materials, and its characteristics were investigated. Furthermore,inauences by annealinσ of the characteristics of these thin f11ms arld solar ce11S 、刃ereinvestigated、 The fabrication method of thin alm solar ceⅡ Using cU2Znsnse4 Compound isUnprecedented, and our proposed method in this chapter is the firsttime. The film compositions,the film structures, the alm morph010gies, ce11 Perform飢Ces of these thin 61ms and solar ce11S、Nere characterized by electron probe microanalysis, X・ray dif介action, Raman spectroscopy,
Scanning electron microscopy, quantum efficiencies, and current‑voltage characteristics
measurements, and these propedies 、vere discussed. The solar ce11S fabricated by this process
had qU帥tum e錨Ciency in the wavelength r飢ge between 350 nm and 140o nm. Therefore,theProposed method can be effectively used to produce thin films characterized by 、uide quantum
e価Ciency ranges.

Next,the cU2SnS3 血in f11ms and solar ce11S were fabricated by sulfurization process nom 血eStacked cu/sn precursors deposited by sequential evaporation of sn and cu elements. The雫一

CU/sn molar ratio of the evaporation materials 、¥as changed, and the optimum value of theCU/sn molar ratio was invest地ated. The film composition, the film structure, the almmorph010gy, and ce11 Perfbrmances of these thin films and solar ce11S were discussed. The
Iargest open・circuit voltage of247.5 mv 、vas obtained 、刃ith cu/sn molar ratio of l.67, therefore
it is considered thatthe optimum value ofcu/sn molar ratio ofthe evaporation materials in thisfabrication method is vicinity of l.67.
In addition, the ea'ects to the characteristics ofthe cU2SnS3 thin films and solar ce11S by thealkaline metals dopino such as sodium arld potassium 、Nere investigated. The alm composition,
the film structure, the alm morph010gy, ceⅡ Pedormances and quantum e缶Ciencies of theCU2SnS3 thin 釧ms and solar ceⅡS fabricated with alkaline metals doping 、Nere discussed. By
Sodium addition, the cU2SnS3 thin films and solar ce11S 、vere fabricated by sulfurization from theNaF/CU/sn stacked precursor deposited by the sequential evaporation of sn, cu and NaF. TheCeⅡ Performances of these cU2SnS3 Solar ce11S had an uP圦lard trend 、vith increasing NaF/CUmolar ratio, and the cU2SnS3 Solar ceⅡ Which 、Nas fabricated 、vith NaF/CU = 0.075 molar ratioゞdemonstrated the record conversion e伍Ciency of the cU2SnS3 Solar ce11S of 4.63%. By
Potassium addition, CU2SnS3 Solar ce11S fabricated by annealing KF/釧m・bilayer samples(film・bilayer means the thin film fabricated by sU1員lrization fiom the NaF/CU/sn stackedPrecursor) demonstrated the open‑circuit voltage of293 mv.
Fina11y, the effects of Ag doping on the characteristics of cU2SnS3 thin films and solar ce11S
Were investigated. The (CU,Ag)2SnS3 thin films and solar ce11S 、和hich 、刃ere Ag doping of cTS、vere fabricated by sulfurization from the NaF/sn/(Ag十CU) stacked precursors deposited bySequential evaporation ofAg, cu and sn elements and NaF, and the Ag/(Ag+CU) molarratio ofthe evaporation materials atld the sulfurization temperatures 、vere varied. The film composition,
the 61m structure, the film morph010gy, ce11 Performances and quantum efficiencies of the(CU,Ag)2SnS3 thin films and solar ce11S 、Nere discussed. The lattice spacing increased along
Vegard's la、N 、Nith increasing the Ag/(Ag十CU) molar ratio in alms, and it is considered that the(CU,Ag)2SnS3 Was fabricated. The best solar ce11 fabricated 、¥ith Ag/'(Ag十CU)= 0.05 at
Sulfurization temperature of 570 ゜c showed the conversion e伍Ciency of4.07%, and it was the行rst reports of (CU,Ag)2SnS3 thin f11m solar ce11S. Furthermore, the expansion of the band・gap
energy 、vas seen with increasing the Ag/(Ag+CU) molarratio.