Studies on CuInSe2 thin-film solar cell by using electrochemical deposition

Abstract

In this thesis electrochemical analyses were used to investigate the mechanism of electrodeposition process of thin film solar cell of Cu In Ga and Se compounds Electrodeposition is a promising method for forming metal and semiconductor thin films due to its excellent gap-filling capacity and high throughput Low cost mass production can be achieved because of large area plating under non-vacuum circumstances However there are several challenges of crystallinity and smooth films for applying electrodeposition to advanced thin film production Electrochemical analyses such as cyclic-voltammetry stripping (CVS) and linear scan voltammetry (LSV) are the major tools to investigate the composition of plating electrolytes Electrodeposition is a major technology to deposit complex metallic layers It is scalable at low cost as compared to technologies requiring high vacuum Therefore electrodeposition has been developed for the applications of photovoltaics CuInGaSe2 (CIGS) has been spotlighted for its applications in thin film solar cells Single step electrodeposition is the most promising electrochemical technique to produce the CIGS film for solar cell applications However the composition of the CIGS film is hard to control in a ternary solution The variation of electrolyte concentrations is restricted for single potential electrodeposition LSV is an important method to investigate the influences of additives and the competitions of the Cu/In/Ga/Se In the conventional deposition the concentrations of electrolytes are restricted due to the correspondent plating potential of each ion to achieve a specific atomic ratio of the CIGS film The electrodeposition methods of heating solution and substrate solution and photo-assistedwas used in the CIGS deposition to improve the film quality and adjust the atomic ratio of the CIGS film and we applied the pressurized annealed methods to made crystallinity CIGS films; at last electrochemical etching changed the surface atomic ratio of the CIGS film toincreasethe conversion efficiency of CIGS solar cells by made OVC(order vacancy compound) layer The CIGS solar cells though the improved process by this work the Voc was improved from 69 mV to 374 mV the fill factor from 26 3 % to 55 % and the conversion efficiency from 0 49 % to 7 12 % The solar cell of sputter CIGS films after electrochemical the Voc was improved from 650 mV to 693 mV the fill factor from 58 % to 65 % and the conversion efficiency from 11 4 % to 13 8 %

Date of Award	2015 May 28
Original language	English
Supervisor	Wen-Shi Lee (Supervisor)