Ink engineering approach boosts efficiency and cuts cost of quantum dot-based photovoltaics

Colloidal quantum dots (CQDs) are tiny semiconductor particles which are just some nanometers in measurement, that are synthesized in a liquid answer (i.e., colloid). These single-crystal particles, created by breaking down bulk supplies through chemical and bodily processes, have proved to be promising for the event of photovoltaic (PV) applied sciences.

Quantum dot-based PVs may have varied benefits, together with a tunable bandgap, larger flexibility and answer processing. Nonetheless, quantum dot-based solar cells developed up to now have been discovered to have important limitations, together with decrease efficiencies than typical silicon-based cells and excessive manufacturing prices, because of the costly processes required to synthesize conductive CQD movies.

Researchers at Soochow University in China, the University of Electro-Communications in Japan and different institutes worldwide just lately launched a brand new technique that would probably assist to enhance the efficiencies of quantum-dot primarily based photovoltaics, whereas additionally decreasing their manufacturing prices. Their proposed method, outlined in a paper published in Nature Vitality, entails the engineering of lead sulfide (PbS) CQD inks used to print movies for photo voltaic cells.

“When people discuss colloidal quantum dots (CQDs), the first thing that comes to mind is their extremely attractive size-dependent quantum properties, as well as the compatibility with low-cost solution-based fabrication methods, which open up exciting possibilities for next-generation semiconductor materials especially in printable solar cells and optoelectronic devices,” Guozheng Shi and Zeke Liu, co-author of the paper, advised Tech Xplore.

“However, these potential applications are often overshadowed by the complex and expensive synthesis and manufacturing processes required to produce conductive CQD films.”

The delicate and costly processes presently used to supply conductive CQD movies attain a restricted yield, with the prices of CQD lively layers starting from $0.25 to $0.84/Wp, that are too excessive for his or her commercialization. Furthermore, present processes supply restricted management over the standard of the supplies and thus the ensuing photo voltaic cells.

“Earlier than our work, CQD photo voltaic modules exceeding 10 cm² achieved solely ~1% power conversion efficiency (PCE), a stark distinction to the over 12% PCE of lab-scale units (0.04 cm²),” mentioned Liu. “This efficiency gap, combined with costly and complex methods involving hot injection and ligand exchange, made commercial-scale CQD photovoltaics almost impractical. The efficiency gap, along with costly methods, has made commercial-scale CQD photovoltaics impractical.”

The first goal of the latest work by Liu and his colleagues was to facilitate the long run improvement of PVs primarily based on quantum dots, enabling the low-cost manufacturing of large-area and environment friendly photo voltaic cells. In an effort to fulfill this purpose, they launched a brand new ink engineering method that would assist the manufacturing of CQD movies.

“To fabricate large-area conductive quantum dot films, these particles need to be uniformly and tightly stacked while maintaining their individual states to preserve quantum effects,” defined Liu. “Any inconsistency in size or stacking can lead to energy loss, negatively impacting semiconductor performance. This presents a delicate balance between quantum dot stacking and ligand design.”

Standard approaches to create CQDs depend on sizzling injection strategies to supply quantum dots wrapped in long-chain insulating ligands, adopted by a ligand alternate to shorter chains that reinforces a movie’s conductivity. These approaches are each costly and complicated, thus they’re troublesome to copy on a big scale.

“Ligand exchange processes increase both complexity and material costs, while also causing aggregation and morphological defects, making it difficult to achieve uniformity over large areas,” mentioned Liu. “In contrast, our approach uses a direct synthesis (DS) technique to prepare CQD inks.”

The brand new ink engineering technique devised by Liu and his colleagues permits the synthesis of ion-capped CQDs instantly in a polar solvent, thus eliminating the necessity for complicated ligand alternate processes. Utilizing their method, the researchers had been in a position to print carefully packed conductive CQD movies in a single step.

“To minimize aggregation and fusion, we control the chemical environment of the ink, utilizing a solution chemistry engineering (SCE) strategy for precise tuning of ionic configurations and functionality,” mentioned Liu. “The simplified quantum dot technology and improved ink stability result in stable CQD inks with fewer defects, enabling the large-scale fabrication of quantum dot thin films and photovoltaic devices, all at a cost of less than $0.06/Wp.”

Shi, Liu and their colleagues examined their proposed method in a sequence of assessments and confirmed that it resulted within the manufacturing of extremely steady quantum dot inks. As well as, they uncovered a hyperlink between surface-dominated and irreversible quantum dot interactions and the defects current in printed CQD movies, in addition to the efficiency of large-area photo voltaic cells primarily based on these movies.

“Our efforts led to the creation of the first large-area CQD solar module with a certified power conversion efficiency (PCE) exceeding 10%, marking a significant step forward toward the commercialization of CQD-based photovoltaics,” mentioned Liu.

“In addition, we achieved a highly efficient small-area solar cell with a PCE of 13.40%, setting a new benchmark for CQD technology. These advances are crucial as they address the scalability and cost challenges that have long limited the widespread use of CQD solar cells.”

This latest examine may quickly contribute to the event of low-cost, large-area and extremely performing CQD-based photo voltaic cells and different optoelectronic units, corresponding to near-infrared sensors or instruments for house exploration.

As a part of their subsequent research, Liu and his colleagues plan to additional refine the inks produced utilizing their method, as this might lead to photo voltaic cells with even higher efficiencies, whereas additionally extending their doable real-world purposes.

“We will explore adapting the technology for various quantum dots, including low-toxicity variants, and flexible electronics,” added Liu. “Moreover, we’ll examine their use in fields corresponding to short-wave infrared (SWIR) imager—important parts for advancing reasonably priced AI applied sciences like autonomous autos, sensible robots, and industrial automation.

“Ultimately, our goal is to scale this technology for commercial production, reducing both costs and the environmental impact of quantum dot electronics.”

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