Photovoltaic MaterialS Development of Earth Abundant Copper Zinc Tin Sulfide CZTS Thin Film Absorber and Heterojunction Solar Cells

Abstract

newline The growing energy demand has motivated the researchers to design the efficient, newlinelow cost and eco-friendly photovoltaic (PV) cells. Currently, ~ 80 % of PV market is newlinecaptured by crystalline Si based technology. Among the second-generation solar cells, the newlinethin film CdTe and Cu(In,Ga)Se2 (CIGS) technologies have shown remarkable cell newlineefficiencies of 20.4 % and 20.8 % at laboratory scale and reached to 1GW/yr at newlineproduction level. However, to meet the World s multi terawatt energy demand in the newlinefuture, the cost and scarcity of In and Te as well as the toxicity of Cd , will become newlinemajor barrier for CdTe and CIGS. To address these issues, the quaternary semiconductor, newlineCu2ZnSnS4 (CZTS) has been considered as an excellent material and potential alternative newlineto currently existing CIGS and CdTe technologies due to its suitable opto-electronic newlineproperties and, devoid of toxicity and expensiveness. The predicted theoretical efficiency newlinefor CZTS based absorbers were 31 %, however, the achieved practical conversion newlineefficiencies of CZTS based devices are 9.2 %. Although the achieved CZTS efficiencies newlineare promising, but, not remarkable compared to CIGS and CdTe devices. This suggests newlinean in depth studies, mainly, understanding the growth behavior of CZTS and its newlinefundamental properties, which plays a vital role in improving the efficiencies. Hence, a newlinePh.D. work with a focus on the development of CZTS absorbers followed by the newlinefabrication of CZTS heterojunction solar cell was undertaken. In this work, first, we newlinesystematically studied the two step growth of CZTS thin films, which comprises of co newlineand sequential sputter deposition of Cu, Zn and Sn followed by heat a treatment in the newlineambience of sulfur vapor (sulfurization) using two zone furnace. Different newlinecharacterization techniques were used to understand the growth behavior and newlinefundamental properties of the CZTS films and finally optimized various process newlineparameters such as sulfurization temperature, time and metallic stacking order for newlineobtaining device quality