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A new dye shakes up solar cells

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A new dye shakes up solar cells

In 1991, scientists Brian O’Regan and Michael Gratzel at EPFL published a seminal paper describing a new type of solar cell: the dye-sensitized solar cell (DSSC), also known as “Gratzel cell”.

Simple and cheap to build while being flexible and versatile, DSSCs are already manufactured on a multi-megawatt scale, cutting a significant slice of the photovoltaic market, which currently supplies almost 3% of all the world’s electricity, well in the race to reduce carbon emissions.

Now, Dan Zhang and Marko Stojanovic, two PhD students in Gratzel’s lab at EPFL’s School of Basic Sciences, have led the development of a simple dye for DSSCs, called MS5. In devices, this new sensitizer can either be used as single dye, and produce an open-circuit voltage – the maximum voltage a solar cell can reach in full sunlight – of 1.24 Volts or as co-sensitizer, along with the commercial dye XY1b, and enable a power conversion efficiency of 13.5 %. Both are among the highest in the field of DSSCs.

The team used this new dye in combination with another organic sensitizer coded XY1b. Apart from absorbing photons from the blue and yellow domain of the solar emission, the role of the new dye in this tandem is to boost the voltage output of the device by retarding the recombination of charge carriers generated by light. Called MS5, the photosensitizer was used with a copper (II/I) electrolyte to enable the DSSC achieve its impressive efficiency.

“Our work constitutes an important breakthrough in the work of DSSCs and especially dye design,” says Michael Gratzel. “It shows that high performances are achievable with a relatively simple dye through judicious molecular engineering of the sensitizer’s molecular structure.”

Tested under ambient light conditions, the dye showed impressive performance, which is crucial for photovoltaics to be effective under cloudy conditions, or in-door applications to power electronic devices applied e.g. for the internet of things. And last but not least, MS5 is easy to synthesize up to the gram scale using a one-step procedure that researchers describe in their paper.

“Our results not only push the field of dye-sensitized solar cells further, but demonstrate EPFL’s leading expertise in the field,” says Marko Stojanovic.

The work is published in Nature Communications.

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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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