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Group V doping in CdSeTe device can improve power conversion efficiency (PCE) and device stability. Arsenic (As) incorporation into CdSeTe has been demonstrated via both in situ and ex situ techniques; however, optimizing the back contact for group V‐doped CdSeTe devices remains a critical challenge. Here, solution‐processed arsenic chalcogenides (i.e., As₂Te₃and As₂Se₃) as dual‐role materials, serving as both dopants and back‐contact materials for high‐efficiency CdSeTe devices, are investigated. During the formation of the back contact, a portion of the arsenic chalcogenides diffuses into the CdSeTe absorber, facilitating p‐type doping. The remaining materials forms a stable back‐contact layer that facilitate carrier collection and reducing recombination losses at the CdSeTe back surface. Particularly, CdSeTe device employing Te rich As₂Te₃layer as the dopant and back‐contact materials achieves a PCE of 18.34%, demonstrating the dual functionality of solution‐processed arsenic chalcogenides in simultaneously doping the absorber and optimizing charge extraction. This solution based cost‐effective As doping approach offers a promising pathway for advancing CdSeTe photovoltaic technology. 

The tandem solar cell presents a potential solution to surpass the Shockley–Queisser limit observed in single-junction solar cells. However, creating a tandem device that is both cost-effective and highly efficient poses a significant challenge. In this study, we present proof of concept for a four-terminal (4T) tandem solar cell utilizing a wide bandgap (1.6–1.8 eV) perovskite top cell and a narrow bandgap (1.2 eV) antimony selenide (Sb2Se3) bottom cell. Using a one-dimensional (1D) solar cell capacitance simulator (SCAPS), our calculations indicate the feasibility of this architecture, projecting a simulated device performance of 23% for the perovskite/Sb2Se3 4T tandem device. To validate this, we fabricated two wide bandgap semitransparent perovskite cells with bandgaps of 1.6 eV and 1.77 eV, respectively. These were then mechanically stacked with a narrow bandgap antimony selenide (1.2 eV) to create a tandem structure, resulting in experimental efficiencies exceeding 15%. The obtained results demonstrate promising device performance, showcasing the potential of combining perovskite top cells with the emerging, earth-abundant antimony selenide thin film solar technology to enhance overall device efficiency. 

Antimony selenide (Sb₂Se₃) emerges as a promising sunlight absorber in thin film photovoltaic applications due to its excellent light absorption properties and carrier transport behavior, attributed to the quasi‐one‐dimensional Sb₄Se₆‐nanoribbon crystal structure. Overcoming the challenge of aligning Sb₂Se₃‐nanoribbons normal to substrates for efficient photogenerated carrier extraction, a solution‐processed nanocrystalline Sb₂(S,Se)₃‐seeds are employed on the CdS buffer layer. These seeds facilitate superstrated Sb₂Se₃thin film solar cell growth through a close‐space sublimation approach. The Sb₂(S,Se)₃‐seeds guided the Sb₂Se₃absorber growth along a [002]‐preferred crystal orientation, ensuring a smoother interface with the CdS window layer. Remarkably, Sb₂(S,Se)₃‐seeds improve carrier transport, reduce series resistance, and increase charge recombination resistance, resulting in an enhanced power conversion efficiency of 7.52%. This cost‐effective solution‐processed seeds planting approach holds promise for advancing chalcogenide‐based thin film solar cells in large‐scale manufacturing. 

Abstract Antimony selenide (Sb₂Se₃) has excellent directional optical and electronic behaviors due to its quasi‐1D nanoribbons structure. The photovoltaic performance of Sb₂Se₃solar cells largely depends on the orientation of the nanoribbons. It is desired to grow these Sb₂Se₃ribbons normal to the substrate to enhance photoexcited carrier transport. Therefore, it is necessary to develop a strategy for the vertical growth of Sb₂Se₃nanoribbons to achieve high‐efficiency solar cells. Since antimony sulfide (Sb₂S₃) and Sb₂Se₃are from the same space group (Pbnm) and have the same crystal structure, herein an ultrathin layer (≈20 nm) of Sb₂S₃has been used to assist the vertical growth of Sb₂Se₃nanoribbons to improve the overall efficiency of Sb₂Se₃solar cell. The Sb₂S₃thin layer deposited by the hydrothermal process helps the Sb₂Se₃ribbons grow normal to the substrate and increases the efficiency from 5.65% to 7.44% through the improvement of all solar cell parameters. This work is expected to open a new direction to tailor the Sb₂Se₃grain growth and further develop the Sb₂Se₃solar cell in the future.