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Use of perovskite will be a key feature of the next generation of electronic appliances

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Use of perovskite will be a key feature of the next generation of electronic appliances

Quantum dots are manmade nanoparticles of semiconducting material comprising only a few thousand atoms. Because of the small number of atoms, a quantum dot’s properties lie between those of single atoms or molecules and bulk material with a huge number of atoms. By changing the nanoparticles’ size and shape, it is possible to fine-tune their electronic and optical properties – how electrons bond and move through the material, and how light is absorbed and emitted by it.

Thanks to increasingly refined control of the nanoparticles’ size and shape, the number of commercial applications has grown. Those already available include lasers, LEDs, and TVs with quantum dot technology.

However, there is a problem that can impair the efficiency of devices or appliances using this nanomaterial as an active medium. When light is absorbed by a material, the electrons are promoted to higher energy levels, and when they return to their fundamental state, each one can emit a photon back to the environment. In conventional quantum dots the electron’s return trip to its fundamental state can be disturbed by various quantum phenomena, delaying the emission of light to the exterior.

The imprisonment of electrons in this way, known as the “dark state”, retards the emission of light, in contrast with the path that lets them return quickly to the fundamental state and hence to emit light more efficiently and directly (“bright state”).

This delay can be shorter in a new class of nanomaterial made from perovskite, which is arousing considerable interest among researchers in materials science as a result (read more at: agencia.fapesp.br/32682/).

A study conducted by researchers in the Chemistry and Physics Institutes of the University of Campinas (UNICAMP) in the state of Sao Paulo, Brazil, in collaboration with scientists at the University of Michigan in the United States, made strides in this direction by providing novel insights into the fundamental physics of perovskite quantum dots.

“We used coherent spectroscopy, which enabled us to analyze separately the behavior of the electrons in each nanomaterial in an ensemble of tens of billions of nanomaterials. The study is groundbreaking insofar as it combines a relatively new class of nanomaterials – perovskite – with an entirely novel detection technique,” Lazaro Padilha Junior, principal investigator for the project on the Brazilian side, told Agencia FAPESP.

FAPESP supported the study via a Young Investigator Grant and a Regular Research Grant awarded to Padilha.

“We were able to verify the energy alignment between the bright state [associated with triplets] and the dark state [associated with singlets], indicating how this alignment depends on the size of the nanomaterial. We also made discoveries regarding the interactions between these states, opening up opportunities for the use of these systems in other fields of technology, such as quantum information,” Padilha said.

“”Owing to the crystal structure of perovskite, the level of bright energy divides into three, forming a triplet. This provides various paths for excitation and for the electrons to return to the fundamental state. The most striking result of the study was that by analyzing the lifetimes of each of the three bright states and the characteristics of the signal emitted by the sample we obtained evidence that the dark state is present but located at a higher energy level than two of the three bright states.

This means that when light is shone on the sample the excited electrons are trapped only if they occupy the highest bright level and are then shifted to the dark state. If they occupy the lower bright levels, they return to the fundamental state more efficiently.”

To study how electrons interact with light in these materials, the group used multidimensional coherent spectroscopy (MDCS), in which a burst of ultrashort laser pulses (each lasting about 80 femtoseconds, or 80 quadrillionths of a second) is beamed at a sample of perovskite chilled to minus 269 degrees Celsius.

“The pulses irradiate the sample at tightly controlled intervals. By modifying the intervals and detecting the light emitted by the sample as a function of the interval, we can analyze the electron-light interaction and its dynamics with high temporal precision, mapping the typical interaction times, the energy levels with which they couple, and the interactions with other particles,” Padilha said.

The MDCS technique can be used to analyze billions of nanoparticles at the same time and to distinguish between different families of nanoparticles present in the sample.

The experimental system was developed by a team led by Steven Cundiff, principal investigator for the study at the University of Michigan. Some of the measurements were made by Diogo Almeida, a former member of Cundiff’s team and now at UNICAMP’s ultrafast spectroscopy laboratory with a postdoctoral fellowship from FAPESP under Padilha’s supervision.

Quantum dots were synthesized by Luiz Gustavo Bonato, a PhD candidate at UNICAMP’s Chemistry Institute. “The care Bonato took in preparing the quantum dots and his protocol were fundamentally important, as evidenced by their quality and size, and by the properties of the nanometric material,” said Ana Flavia Nogueira, co-principal investigator for the study in Brazil. Nogueira is a professor at the Chemistry Institute (IQ-UNICAMP) and principal investigator for Research Division 1 at the Center for Innovation in New Energies (CINE), an Engineering Research Center (ERC) established by FAPESP and Shell.

“”The results obtained are very important since knowledge of the optical properties of the material and how its electrons behave opens up opportunities for the development of new technologies in semiconductor optics and electronics. The incorporation of perovskite is highly likely to be the most distinctive feature of the next generation of television sets,” Nogueira said.

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Innovative approach to perovskite solar cells achieves 24.5% efficiency

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Innovative approach to perovskite solar cells achieves 24.5% efficiency


Innovative approach to perovskite solar cells achieves 24.5% efficiency

by Simon Mansfield

Sydney, Australia (SPX) Mar 28, 2024






In groundbreaking research published in Nano Energy, a team led by Prof. CHEN Chong at the Hefei Institutes of Physical Science, part of the Chinese Academy of Sciences, has significantly improved the performance of perovskite solar cells (PSCs). By integrating inorganic nano-material tin sulfoxide (SnSO) as a dopant, they have boosted the photoelectric conversion efficiency (PCE) of PSCs to an impressive 24.5%.

Traditional methods of enhancing the charge transport in the critical hole transport layer (HTL) of PSCs involve the use of lithium trifluoromethanesulfonyl imide (Li-TFSI) to facilitate the oxidation of the HTL material spiro-OMeTAD. However, this method suffers from low doping efficiency and can leave excess Li-TFSI in the spiro-OMeTAD film, reducing its compactness and long-term conductivity. Additionally, the oxidation process typically requires 10-24 hours to achieve the desired electrical conductivity and work function.



The HFIPS team’s innovation lies in their development of a rapid and replicable method to control the oxidation of nanomaterials, using SnSO nanomaterial to pre-oxidize spiro-OMeTAD in precursor solutions. This novel approach not only enhances conductivity but also optimizes the energy level position of the HTL, culminating in a high PCE of 24.5%.



One of the key advantages of the SnSO-regulated spiro-OMeTAD HTL is its pinhole-free, uniform, and smooth morphology, which maintains its performance and physical integrity even under challenging conditions of high temperature and humidity. Additionally, the oxidation process facilitated by this method is significantly faster, taking only a few hours- a crucial factor in improving the commercial production efficiency of PSCs.



Prof. CHEN Chong highlighted the importance of this breakthrough, stating, “Also, the oxidation process only takes a few hours, which is good for improving the commercial preparation efficiency of PSCs.” This advancement not only marks a significant leap in the efficiency and stability of PSCs but also holds substantial implications for their commercial viability.



Research Report:A nanomaterial-regulated oxidation of hole transporting layer for highly stable and efficient perovskite solar cells


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Revolutionary technique boosts flexible solar cell efficiency to record high

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Revolutionary technique boosts flexible solar cell efficiency to record high


Revolutionary technique boosts flexible solar cell efficiency to record high

by Simon Mansfield

Sydney, Australia (SPX) Mar 28, 2024






Researchers at Tsinghua University have made a significant breakthrough in the efficiency of flexible solar cells, leveraging a novel fabrication technique to set a new efficiency record. This advancement addresses the longstanding challenge of the lower energy conversion efficiency in flexible solar cells compared to their rigid counterparts, offering promising implications for aerospace and flexible electronics applications.

Flexible perovskite solar cells (FPSCs), despite their potential, have historically lagged in efficiency due to the polyethylene terephthalate (PET)-based flexible substrate’s inherent softness and inhomogeneity. This limitation, coupled with durability issues arising from the substrate’s susceptibility to water and oxygen infiltration, has hindered the practical deployment of FPSCs.



The team from the State Key Laboratory of Power System Operation and Control at Tsinghua University, alongside collaborators from the Center for Excellence in Nanoscience at the National Center for Nanoscience and Technology in Beijing, introduced a chemical bath deposition (CBD) technique. This method facilitates the deposition of tin oxide (SnO2) on flexible substrates without the need for strong acids, which are detrimental to such substrates. Tin oxide is essential for the FPSCs as it acts as an electron transport layer, crucial for the cells’ power conversion efficiency.



Associate Professor Chenyi Yi, a senior author of the study, explained, “Our method utilizes SnSO4 tin sulfate instead of SnCl2 tin chloride, making it suitable for acid-sensitive flexible substrates. This approach not only enhances the efficiency of FPSCs but also their durability, with a new power conversion efficiency benchmark set at 25.09%, certified at 24.90%.”



The novel fabrication technique also contributes to the FPSCs’ stability, as demonstrated by the cells maintaining 90% of their initial efficiency after being bent 10,000 times. The researchers noted an improved high-temperature stability in SnSO4-based FPSCs over those made with SnCl2, pointing towards the dual benefits of efficiency and durability enhancements.



The research signifies a leap towards industrial-scale production of high-efficiency FPSCs, with potential applications ranging from wearable technology and portable electronics to aerospace power sources and large-scale renewable energy solutions. The team’s findings, supported by Ningyu Ren, Liguo Tan, Minghao Li, Junjie Zhou, Yiran Ye, Boxin Jiao, and Liming Ding, mark a pivotal step in transitioning FPSCs from laboratory to commercial use.



Research Report:25% – Efficiency flexible perovskite solar cells via controllable growth of SnO2


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KAUST advances in perovskite-silicon tandem cells

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KAUST advances in perovskite-silicon tandem cells


KAUST advances in perovskite-silicon tandem cells

by Sophie Jenkins

London, UK (SPX) Mar 28, 2024






In 2009, researchers introduced perovskite-based solar cells, highlighting the potential of methylammonium lead bromide and methylammonium lead iodide-known as lead halide perovskites-for photovoltaic research. These materials, notable for their excellent light-absorbing properties, marked the beginning of an innovative direction in solar energy generation. Since then, the efficiency of perovskite solar cells has significantly increased, indicating a future where they are used alongside traditional silicon in solar panels.

Erkan Aydin, Stefaan De Wolf, and their team at King Abdullah University of Science and Technology (KAUST) have explored how this tandem technology could transition from experimental stages to commercial production. Perovskites are lauded for their low-temperature production process and their flexibility in application, offering a lighter, more adaptable, and potentially cost-effective alternative to silicon-based panels.



Combining perovskite with silicon in a single solar cell leverages the strengths of both materials, enhancing sunlight utilization and reducing losses that aren’t converted into electrical energy. “The synergy between perovskite and silicon technologies in tandem cells captures a broader spectrum of sunlight, minimizing energy loss and significantly boosting efficiency,” Aydin notes.



However, Aydin and his colleagues acknowledge challenges in scaling tandem solar-cell fabrication for the marketplace. For instance, the process of depositing perovskite on silicon surfaces is complicated by the silicon’s texture. Traditional laboratory methods like spin coating are not feasible for large-scale production due to their inefficiency and material wastage. Alternatives such as slot-die coating and physical vapor deposition present their own set of advantages and challenges.



Moreover, the durability of perovskite components under environmental stressors such as moisture, heat, and light remains a critical concern. Aydin emphasizes the need for focused research to enhance the reliability and lifespan of perovskite/silicon tandem cells, especially in harsh conditions.



Although tandem modules have already been demonstrated in proof-of-concept stages, the timeline for their market readiness is uncertain. Nonetheless, the successful development of efficient, commercial-grade perovskite/silicon solar cells is essential for meeting global energy demands sustainably.



Research Report:Pathways toward commercial perovskite/silicon tandem photovoltaics


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All About Solar Energy at SolarDaily.com





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