Effect of alkali doping on CIGS photovoltaic ceramic tiles

This report studies the influence of alkali elements (Na, K) to morphological, structural and optoelectronic properties of CIGS ceramic tile solar cell. Several ceramic enamels with altered chemical composition in terms of amount of alkali elements have been tested and compared. The influences of alkali type, its quantity and transfer mechanism have been investigated. The solar cell device has been assembled and characterized. The achieved results indicate that alkali elements (Na and K combination) modified the surface roughness and its diffusion from the enamel toward the absorber affect to the structural and final optoelectronic properties of the device. The alkali doping improve the Ga incorporation in the crystal lattice and an increasing in open circuit voltage (Voc) values, fill factor (FF) and the device efficiency. Optimal alkali quantities have been also determined. The best conversion efficiency is achieved for the cell with 4% wt Na2O and 3.2 % wt K2O (Eff. = 3,5 %), which presents an improvement of 30 % in efficiency relative to the standard (STD) solar cell sample chosen for comparative purposes