Investigation on the role of Sb doping on grain growth and properties of solution-processed CuIn(S,Se)2

Cu(In,Ga)(S,Se) 2 (CIGSSe) has been one of the most promising materials used for photovoltaic application.Solution based synthesis of CuIn(S,Se) 2 (CISSe) cells have achieved 12% efficiency, utilizing toxic hydrazine as the solvent.A shift towards an environmental friendly approach for CIS fabrication is thus necessary.In this thesis, solvothermal syntheses of wurtzite and chalcopyrite CIS nanoparticles are explored.Metastable wurtzite nanoparticles were successfully synthesized at much lower temperature, with a dual amine solvent under excess sulfur environment.Binary Cu 9 S 5 and In 2 S 3 nanoparticles were also synthesized and spray deposited to make a film.However, nanoparticle deposition resulted in rough and non-uniform film.Hence, aqueous spray pyrolysis of precursor solution was deployed to form CIS film directly on Mo substrate.Oxidation of Mo substrate is avoided by deposition of a precursor layer which acts as a barrier layer isolating Mo surface.The resultant film is dense and uniform but has very fine grains which are detrimental to carrier transport.A hybrid approach using nanoparticles incorporated into precursor solution for spray pyrolysis results in dense and uniform film, with significantly larger grains after selenization.However, the hybrid approach involves complex processing and precise experimental control.Hence, aqueous spray pyrolysis of precursor solution is a better option.High temperature annealing can enhance grain size of spray pyrolysed CIS film.Annealing under different vapors, namely S, Se and Ar, provides different extent of grain growth.Annealing in Se vapor, selenization, results in the most significant grain growth, due to the abundant formation of liquid Cu x Se phases which enhances grain growth by liquid phase sintering.Annealing in S vapor is less efficient due to increased difficulty in liquid phase First and foremost, I would like to express my gratitude to my supervisor and co-supervisors, Assoc.Prof Alfred Tok and Asst.Prof Lydia Wong for the guidance, encouragement and patience throughout the progress of my research work.The numerous active discussions and valuable suggestions given by both supervisors throughout the progress of my work have benefited and assisted me greatly in my research work.I would also like to thank Prof Subodh Mhaisalkar for providing lab facilities for me to conduct my research.Furthermore, the numerous discussions during research group meetings have benefited me greatly.I would like to thank Prof Lam Yeng Ming for the advice and suggestions offered during research group meetings.I would also like to thank Dr Sudip Batabyal for being a wonderful mentor in my research work.His innovative ideas, helpful suggestions and constant guidance are deeply appreciated.I would like to