Preparation Of Zn(O,S) Buffer Layer Thin Films And Their Application In Solar Calls

Zn(O,S)thin film is a typical II-VI compound semiconductor material with high bandgap energy(Eg),in the range between 2.6 eV and 3.6 eV depending on the difference of oxygen and sulfur content,which can also control the conduction band offset(CBO)between the absorption and buffer.It has many advantages,such as abundant raw materials,cheap cost in the earth and adjustable band offset.Therefore,it is considered as one of the most promising alternatives to CdS buffer layer.In this thesis,Zn(O,S)thin films were synthesized on glass substrates by oxidizing ZnS thin films in an atmosphere of pure oxygen deposited by electron beam evaporation method.The influences of the preparation parameters on the structure,composition,surface morphology,optical and electrical properties of the Zn(O,S)thin films were investigated.In the meantime,the ?-? characteristic curves of CZTS/Zn(O,S)and SnS/Zn(O,S)heterojunctions were studied.The main results are demonstrated as follows.1.The influences of the oxidizing temperature and time on the structure,surface morphology,composition and photoelectric properties of the Zn(O,S)thin films were studied.Experimental results show that,with the increasing of the oxidizing temperature,the structure of the Zn(O,S)thin films changes greatly.The oxygen component of the thin films is increased gradually,but the sulfur component of the thin films is decreased gradually.The surface of the films appears denser and smoother trend.The optical band gap is decreased gradually,and the resistivity is decreased first and then increased.With increasing the oxidizing time,the oxygen component of the thin films is basically constant,and the surface morphology of the films gets better.With increasing the oxidizing time,the optical band gap is decreased gradually,but the resistivity is increased gradually.The Zn(O,S)thin films exhibit better photoelectric properties than others when the oxidizing temperature and time of the Zn(O,S)was 400? and 2.0 h,respectively.The optical band gap and the resistivity of Zn(O,S)thin film are 3.36 eV and 3.22×103 ?·cm,respectively.The results show the Zn(O,S)flims are suitable for the buffer layers of the solar cells.2.The influences of the oxidizing temperature,oxidizing time and thickness of Zn(O,S)buffer layers on the ?-? characteristic curves of the CZTS/Zn(O,S)heterojunctions were investigated.The experimental results show that,the CZTS/Zn(O,S)heterojunctions show good rectifying characteristics when the oxidizing temperature,oxidizing time and thickness of Zn(O,S)buffer layers are 400?,2.0 h and 100 nm,respectively.3.The influences of the oxidizing temperature,oxidizing time,thickness of Zn(O,S)buffer layers and the annealing temperature of SnS absorption layers on the?-? characteristic curve of the SnS/Zn(O,S)heterojunction were investigated.The experimental results show that,the SnS/Zn(O,S)heterojunction express good rectifying characteristics and best photoresponse characteristics when the oxidizing temperature,oxidizing time,thickness of Zn(O,S)buffer layers and annealing temperature of the SnS absorption layers are 450?,2.0 h,150 nm and 250?,respectively.