Preparation And Characterization Of ZnSe Thin Films By Electrodeposition

Nanocrystal photo-eletrochemical cells (NPC) and extremely thin absorber solar cells (ETA) have been widely studied according to their low cost and simple technology. In this paper, an overview about the development of various kind of solar cells was given. The electrodeposition of ZnSe as a candidate for buffer layers of NPC and ETA solar cells was studied. Furthermore, the deposition mechanism of ZnSe on transparent conductive oxides (TCO) was discussed.Pure, cubic ZnSe films in coincidence with stoichiometry were fabricated on TCOs by potentiostatic deposition from electrolytes containing ZnSO₄ and SeO₂. XRD, SEM, EDS and UV-VIS were employed to characterize the composition, surface and cross-section pattern, transmittance and energy band gap of ZnSe films.The experimental results showed that, SeO₃^2- was an active substance in the electrolyte and the inert substance K2SO4 could significantly improve the crystallization and deposition of ZnSe while the action of the complexing agent Na₂EDTA was small. It was possible to fabricate films with good characters on various substrates in the condition that the temperature was fixed at 70℃, the pH value was 2.4 and the deposition potential was in the range of -900 mV～-1100 mV.Substrates greatly affected the deposition process, morphology and properties of the as-prepared films. The in-situ catalysis reaction of H₂Se directly resulted in the difficulty of ZnSe deposition on TCOs. Pure cubic ZnSe films were finally obtained by violently stirring of electrolytes to reduce the in-situ reaction of H₂Se. Moreover, the stoichiometry of films could be effectively improved by calcination in running Ar in spite of the excess of selenium contents in various films.