Please use this identifier to cite or link to this item:
Preparation and Photovoltaic Characterization of Solution-coated Cu(In,Ga)Se2 Thin-Film Solar Cells
solution coating process,CIGS,thin-film solar cells,
|Publication Year :||2016|
Chalcopyrite-based absorber layers and transparent conducting layers were prepared for the application of Cu(In,Ga)Se2 thin-film solar cells in this thesis. Cu(In,Ga)Se2 films were synthesized via a solution coating route with a non-toxic selenization process. Potassium ions were doped into the solution-coated Cu(In,Ga)Se2 films to reduce the formation of secondary phases and improve the photovoltaic properties of the obtained films. Additionally, sulfur ions were incorporated into Cu(In,Ga)Se2 films for increasing the band gaps and reducing the vacancy defects of selenium near the surface region of the obtained films. For further improving the photovoltaic performance of Cu(In,Ga)Se2 solar cells, Al-doped zinc oxide (AZO) films were prepared as the transparent conducting layers for increasing the optical transmittance in near infrared (NIR) region. The photovoltaic characteristics and diode analysis of the fabricated solar cells were investigated in detail.
For reducing the processing complexity and dangerously, a solution coating process combined with a non-toxic selenization treatment were applied to prepared Cu(In,Ga)Se2 films in the first section of thesis. The increase in Se-vapor flow-rate promoted selenization reaction and grain growth of Cu(In,Ga)Se2 films. Increasing the amount of selenium vapor also elevated the gallium grading profile and enhanced the effects of back surface field. The conversion efficiency of the solar cells achieved 10.21%. The solution-coated Cu(In,Ga)Se2 films selenized with appropriate selenium-vapor flow-rate were presented to be an effective approach for the preparation of Cu(In, Ga)Se2-based absorber layers.
In the second section, for reducing the secondary compounds and improving the photovoltaic properties of absorber layers, potassium ions were added into Cu(In,Ga)Se2 films. The monophasic Cu(In,Ga)Se2 films were obtained as potassium ions were incorporated into the precursor films. The potassium-ion doped Cu(In,Ga)Se2 films with smooth morphology improved the coverage of CdS buffer layer and suppressed the additional shunt paths. The conversion efficiency of the solar cells fabricated without KCN treatment was increased to 10.90 %.
In the third section, the preparation of Cu(In,Ga)(Se,S)2 films via a surface sulfurization treatment followed by selenization process was investigated. After sulfurization treatment, the Cu(In,Ga)(Se,S)2 films with a double-graded band gap profiles were obtained because the incorporation of sulfur-ion into Cu(In,Ga)Se2 films formed an inverse band gap grading near the surface region. The formation of selenium vacancies in the Cu(In,Ga)(Se,S)2 films were effectively reduced with the well-controlled H2S concentration during the sulfurization. The open-circuit voltage of the prepared solar cells was increased, thereby boosting the conversion efficiency to 12.40%.
In the fourth section, the oxygen-doped AZO films were deposited using a reactive sputter process. The increment in the substrate temperatures promoted the grain growth and reduced the grain boundaries of AZO films, thereby resulting in the reduction of resistivity. As oxygen concentration in the sputtering gas was raised, the average transmittance of AZO films in NIR region was increased from 86.2% to 91.4%. The improvement in the optical transmittance of AZO films led to increase the conversion efficiency of solar cells. Moreover, the photovoltaic performance of the potassium-ion doped Cu(In,Ga)(Se,S)2 films was further improved by combining with the modified AZO films. This thesis demonstrated that the new preparation processes for fabricating high-efficiency Cu(In,Ga)Se2-based solar cells were successfully developed.
|Appears in Collections:||化學工程學系|
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.