By introducing a pre-deposited CuGaSe2 layer, a steep Ga back grading has been formed in a submicron CIGS layer with a high-temperature process for the first time.
As an emerging route to further lower the production cost, reducing the thickness of Cu(In,Ga)Se 2 (CIGS) absorber has drawn substantial attention and has been intensively studied in recent years. However, thickness-induced change still limits the device performance of thin CIGS solar cells. Herein, by examining a series of submicron CIGS solar cells with varied Cu content through their photovoltaic (PV) performance, the optimal Cu content in these submicron CIGS devices is found to be lower than that of the normal thickness CIGS devices. Electrical and compositional characterizations reveal that reduced thickness makes absorber vulnerable to the shunt paths formed with high Cu content. By intentionally lowering the Cu content in submicron CIGS, shunt resistance (R sh ) of the devices is significantly improved and therefore a high fill factor (FF) is achieved. Moreover, RbF postdeposition treatment (PDT) can passivate the shunt paths in the high Cu content samples to a very good extent, manifesting by the significantly improved FF.
Zn(O,S) thin film as one of the most promising alternative buffer layers in Cu(In,Ga)Se 2 solar devices has drawn considerable attention and been intensively studied in recent years. However, the reliability of the fabrication process still impeded its industrial application. In this work, a self-designed double-sided heat-exchange chemical bath deposition (CBD) system was introduced to deposit large-area homogeneous Zn(O,S) thin films. Compared with the traditional CBD setup, the self-designed system possesses several advantages including fast heat-up, homogeneous heating, wide adaptability, and cost-saving. Intriguingly, based on the self-designed system, high-quality Zn(O,S) thin films with less amounts of OH − and O 2− impurities were easily and successfully deposited without changing the recipe. Furthermore, we have also demonstrated the homogeneity of the solar cells made from the same substrate with a large area and adopted this technique for the fabrication of modules both in the laboratory and in our partner company Shinetech Co., Ltd. As a preliminary result, over 16% conversion efficiency for rigid modules (53 cm 2 ) and over 10% for flexible modules (36 cm 2 ) based on the self-designed deposition system were obtained. As a consequence, a deeper understanding may be provided to deposit high-quality and large-scale Zn(O,S) thin films and hopefully also applicable to industrial.
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