Study On Preparation And Properties Of CuInS₂ And In₂S₃ Thin Films Materials For Solar Cells By Ultrasonic Sprary Pyrolysis Method

Energy is one of the foundations for the survival and development of human society,Traditional energy causes great damage to the environment, so the solar cells get more andmore people’s attention. CuInS₂ is one of the I-III-VI2 chalcopyrite compounds, which hasbeen regarded as a promising absorber for thin film solar cell applications. It has highabsorption coefficient and high conversion efficiency. In₂S₃ is a very promising bufferlayer as a substitute of CdS for thin films solar cells because it is nontoxic and almosttransparent to visible light.In this paper, preferred orientation of CuInS₂ and In₂S₃ thin films were prepared onglass substrates by ultrasonic spray pyrolysis deposition technique. CuCl₂,InCl₃å'ŒSC（NH₂）₂ acted as copper, indium and sulfur source，and the properties of the thin filmswere investigated by XRD, SEM, four-point probe and UV-Vis spectrometer analysis. Theeffects on properties of films caused by growth parameters （such as the distance betweenthe spray head and the substrate, deposition time, molar ratio, substrate temperature，annealing temperature） are studied. The structure and electrical properties of preparedp-CuInS₂/n-In₂S₃ hetero-junction are studied.As the results shown, CuInS₂ thin films with high quality could be prepared underoptimized deposition condition: distance between spray head and substrate 10cm, reactiontime 10min, substrate temperature 320℃, Cu/In ratio 1.25, The prepared films arerelatively dense and smooth, they have highly preferred orientation along （112） direction.The sheet resistance of CuInS₂ films can come up to 125Ω/sq. The prepared film has astrong visible absorption of 90% and its energy band gap can come up to 1.45eV. Thecrystallinity of CuInS₂ films has been greatly improved when annealing temperature is 500℃in argon ambient. In addition, the grain growth has been improved significantly whenannealing temperature is 500℃, the absorption of film in visible region is enhanced withthe increasing annealing temperature.Prepared In₂S₃ thin films have a preferential orientation along the （220） direction andno other phases are observed. In₂S₃ thin films with high quality could be prepared underoptimized deposition condition: substrate temperature 300℃, S/In = 2. The prepared filmsare relatively dense and smooth and they have a strong optical transmittance of 80% in thevisible region. Its energy band gap come up to 2.46eV. In addition, the transmittance ofas-deposited films was reduced gradually to 50% and the bad gap decreased to 2.37eVafter argon annealing at 400-600℃.Prepared p-CuInS₂/n-In₂S₃ hetero-junction exhibits rectifying properties. The turn-on voltage is obtained around 0.5V。Maximum current obtained at -3V and 3V is around24.8μA and 21.2μA. The obvious leakage current was observed at a reverse bias of -1Vbecause the interface between CuInS₂ and In₂S₃ has defects and lattice mismatch.