RESUMO
Increasing the fill factor (FF) and the open-circuit voltage (VOC ) simultaneously together with non-decreased short-circuit current density (JSC ) are a challenge for highly efficient Cu2 ZnSn(S,Se)4 (CZTSSe) solar cells. Aimed at such target in CZTSSe solar cells, a synergistic strategy to tailor the recombination in the bulk and at the heterojunction interface has been developed, consisting of atomic-layer deposited aluminum oxide (ALD-Al2 O3 ) and (NH4 )2 S treatment. With this strategy, deep-level CuZn defects are converted into shallower VCu defects and improved crystallinity, while the surface of the absorber is optimized by removing Zn- and Sn-related impurities and incorporating S. Consequently, the defects responsible for recombination in the bulk and at the heterojunction interface are effectively passivated, thereby prolonging the minority carrier lifetime and increasing the depletion region width, which promote carrier collection and reduce charge loss. As a consequence, the VOC deficit decreases from 0.607 to 0.547 V, and the average FF increases from 64.2% to 69.7%, especially, JSC does not decrease. Thus, the CZTSSe solar cell with the remarkable efficiency of 13.0% is fabricated. This study highlights the increased FF together with VOC simultaneously to promote the efficiency of CZTSSe solar cells, which could also be applied to other photoelectronic devices.
RESUMO
About 10% efficient antimony selenosulfide (Sb2 (S,Se)3 ) solar cell is realized by using selenourea as a hydrothermal raw material to prepare absorber layers. However, tailoring the bandgap of hydrothermal-based Sb2 (S,Se)3 film to the ideal bandgap (1.3-1.4 eV) using the selenourea for optimal efficiency is still a challenge. Moreover, the expensive selenourea dramatically increases the fabricating cost. Here, a straightforward one-step hydrothermal method is developed to prepare high-quality Sb2 (S,Se)3 films using a novel precursor sodium selenosulfate as the selenium source. By tuning the Se/(Se+S) ratio in the hydrothermal precursor solution, a series of high-quality Sb2 (S,Se)3 films with reduced density of deep defect states and tunable bandgap from 1.31 to 1.71 eV is successfully prepared. Consequently, the best efficiency of 10.05% with a high current density of 26.01 mA cm-2 is achieved in 1.35 eV Sb2 (S,Se)3 solar cells. Compared with the traditional method using selenourea, the production cost for the Sb2 (S,Se)3 devices is reduced by over 80%. In addition, the device exhibits outstanding stability, maintaining more than 93% of the initial power conversion efficiency after 30 days of exposure in the atmosphere without encapsulation. The present work definitely paves a facile and effective way to develop low-cost and high-efficiency chalcogenide-based photovoltaic devices.
RESUMO
Vapor-transport deposition (VTD) method is the main technique for the preparation of Sb2Se3 films. However, oxygen is often present in the vacuum tube in such a vacuum deposition process, and Sb2O3 is formed on the surface of Sb2Se3 because the bonding of Sb-O is formed more easily than that of Sb-Se. In this work, the formation of Sb2O3 and thus the carrier transport in the corresponding solar cells were studied by tailoring the deposition microenvironment in the vacuum tube during Sb2Se3 film deposition. Combined by different characterization techniques, we found that tailoring the deposition microenvironment can not only effectively inhibit the formation of Sb2O3 at the CdS/Sb2Se3 interface but also enhance the crystalline quality of the Sb2Se3 thin film. In particular, such modification induces the formation of (hkl, l = 1)-oriented Sb2Se3 thin films, reducing the interface recombination of the subsequently fabricated devices. Finally, the Sb2Se3 solar cell with the configuration of ITO/CdS/Sb2Se3/Spiro-OMeTAD/Au achieves a champion efficiency of 7.27%, a high record for Sb2Se3 solar cells prepared by the VTD method. This work offers guidance for the preparation of high-efficiency Sb2Se3 thin-film solar cells under rough-vacuum conditions.
