Construction of a Low-Resistivity Carbon Layer To Improve Performance in Dimethyl Sulfoxide-Based Kesterite Solar Cells.

Morphology of the absorber plays a decisive role in photoelectric conversion efficiency (PCE) of kersterite solar cells. Cu2ZnSn(S,Se)4 (CZTSSe) grain prepared from dimethyl sulfoxide (DMSO)-based solution easily grows into large grains, which can lead to the formation of some holes at the back of the absorber. These holes cause the recombination of photocarriers and greatly weaken the performance of CZTSSe devices. Here, trace amounts of thioglycolic acid (TGA) are introduced to the DMSO-based solution, and a combination of TGA and metal is formed in the absorber, leading to the formation of fine grains in the CZTSSe absorber. Next, post-annealing (PA) in a N2 atmosphere is performed to promote Na diffusion, helping the transition from a fine-grain layer to a low-resistivity carbon layer at the interface between CZTSSe and Mo and avoiding the drawbacks of the DMSO-based system. Finally, the champion PCE of the CZTSSe device can be improved to 10.05% from 8.06%. The conclusions demonstrate that the construction of a carbon layer can boost the performance of CZTSSe devices.

Designing advanced S-scheme CdS QDs/La-Bi2WO6 photocatalysts for efficient degradation of RhB.

Finding effective strategies to design efficient photocatalysts and decompose refractory organic compounds in wastewater is a challenging problem. Herein, by coupling element doping and constructing heterostructures, S-scheme CdS QDs/La-Bi2WO6 (CS/LBWO) photocatalysts are designed and synthesized by a simple hydrothermal method. As a result, the RhB degradation efficiency of the optimized 5% CS/LBWO reached 99% within 70 min of illumination with excellent stability and recyclability. CS/LBWO shows improvement in the adsorption range of visible light and promotes electron-hole pair generation/migration/separation, attributing the superior degradation performance. The degradation RhB mechanism is proposed by a free radical capture experiment, electron paramagnetic resonance, and high-performance liquid chromatography-mass spectrometry results, indicating that h+ and •O2 - play a significant role during four degradation processes: de-ethylation, chromophore cleavage, ring opening, and mineralization. Based on in situ irradiated X-ray photoelectron spectroscopy, Mulliken electronegativity theory, and the work function results, the S-scheme heterojunction of CS/LBWO promotes the transfer of photogenerated electron-hole pairs and promotes the generation of reactive radicals. This work not only reports that 5% CS/LBWO is a promising photocatalyst for degradation experiments but also provides an approach to design advanced photocatalysts by coupling element doping and constructing heterostructures.