Hybrids and related materials

As silicon-based transistors approach their limits, researchers are exploring alternative materials to continue progress in semiconductor technology. Carbon nanotubes (CNTs) are considered promising candidates for next-generation electronics due to their exceptional electrical properties and nanoscale dimensions. Yet, the challenge of precisely controlling the electronic characteristics of CNTs has hindered their widespread adoption in practical applications.

Researchers at China's Peking University, Zhejiang University and Chinese Academy of Science (CAS) have developed an inner doping method by filling CNTs with 1D halide perovskites to form a coaxial heterojunction, which enables a stable n-type field-effect transistor for constructing complementary metal–oxide–semiconductor electronics.

Researchers at India's Chitkara University Institute of Engineering and Technology have developed 2D perovskite solar cells with MXene materials to build a PV device with remarkable efficiency and open-circuit voltage. The scientists claim the new cell architecture can help charge carriers move smoothly through the cell layers and reduce recombination losses.

The team's 2D DJ perovskite solar cell implemented bandgap grading techniques and use contacts based on a functionalized two-dimensional titanium carbide known as MXene. MXenes are compounds that take their name from their graphene-like morphology and are made via selective etching of certain atomic layers from a bulk crystal known as MAX. Recently, MXenes materials have shown promise for use in PV technology due to their unique optoelectronic properties, such as their large charge carrier mobility, excellent metallic conductivity, high optical transmittance, and tunable work function (WF).

Perovskite nanocrystals (PNCs)/polymer nanocomposites can combine the advantages of both materials, but achieving the fabrication of PNCs/polymer nanocomposites by bulk polymerization has proven Very challenging. A team of scientists, led by Professor Bai Yang from Jilin University in China, has adopted a a two-type ligand strategy to fabricate bulk PNCs/polystyrene (PS) nanocomposites, including a new type of synthetic polymerizable ligand.

The CsPbCl₃ PNCs/PS nanocomposites reportedly showed extremely high transparency that can be ascribed to the Rayleigh scattering as the PNCs distribute uniformly without obvious aggregation. Based on this behavior, the team first exploited the potential of PNCs to serve as scatters inside light guided plate (LGP), whose surface illuminance and uniformity can be improved, and this new kind of LGP is compatible with advanced liquid crystal display technology. 

Scientists from South Korea have developed a foldable thin-film device with promising characteristics. Integrating a perovskite cell material and a carbon nanotube electrode, the group fabricated a device that achieved 15.2% efficiency and could be folded more than 10,000 times at a bending radius of 0.5mm.

Solar cell materials tend to be quite sensitive. Designing and manufacturing devices that can withstand the stress of being folded and bent is challenging, and many of even the most promising solutions are still quite limited in their flexibility. The scientists at Pusan National University in South Korea took a major step forward in solving this problem, fabricating a device that can be folded down to a 'bending radius' ' the minimum size of fold possible without causing damage ' of 0.5mm.

Solliance and U.S-based MiaSolé announced a new record - power conversion efficiency of 26.5% on a tandem solar cell that combined a top rigid semi-transparent perovskite solar cell with a bottom flexible copper indium gallium selenide (CIGS) cell.

This impressive efficiency was achieved by optimizing the bandgap and the efficiency of both the rigid semi-transparent perovskite top cell and the flexible CIGS bottom cell. The CIGS was roll to roll produced on steel foil, with a power conversion efficiency of 20.0%.

A new EU project called "CITYSOLAR" aims to revolutionize the market for transparent solar cells for windows by combining two photovoltaic (PV) technologies in a tandem configuration. The project has received 3,779,242 EUR in support from the H2020 framework programme. Transparent solar cells for windows have been known for several years, but are still not sufficiently efficient - which is what the new project will attempt to change.

'We develop new innovative concepts within light management and solar module integration that are specifically targeted at new promising organic and hybrid thin film PV technologies, and by that we go significantly beyond state-of-the-art in terms of efficiency for transparent photovoltaics. It's a revolutionary new concept,' says Professor Aldo di Carlo, Cnr-Ism, who is coordinator of the new project and is thrilled about the support of "CITYSOLAR" from the H2020 framework.

An international team of scientists, including ones from King Abdullah University of Science & Technology (KAUST) and University of Toronto, set out to increase the performance of solar panels by creating a bifacial (two-sided) tandem solar cell, made of perovskite and silicon materials.

Image credit: U of T

In outdoor environments, light primarily comes directly from the sun. Conventional tandem solar cells can already convert this light into electricity more efficiently compared to traditional silicon-only solar cells by absorbing additional wavelengths of light. Now, the researchers have realized that even more energy can be gathered using a two-sided tandem configuration. Light reflected and scattered from the ground ' referred to as 'albedo' ' can also be collected to significantly increase the current of a tandem solar cell. The new research outlines how the team engineered the perovskite/silicon device to exceed the currently accepted performance limits for the tandem configuration.

Researchers at HZB have published their recent work, reporting its current world record of 29.15% efficiency for a tandem solar cell made of perovskite and silicon. The tandem cell provided stable performance for 300 hours ' even without encapsulation. To accomplish this, the group, headed by Prof. Steve Albrecht, investigated physical processes at the interfaces to improve the transport of the charge carriers.

In the beginning of 2020, a team headed by Prof. Steve Albrecht at the HZB broke the previous world record for tandem solar cells made of perovskite and silicon (28.0%, Oxford PV), setting a new world record of 29.15%. Compared to the highest certified and scientifically published efficiency, this is a significant step forward. The new value has been certified at Fraunhofer ISE and listed in the NREL chart. Now, the results have been published in the journal Science with a detailed explanation of the fabrication process and underlying physics.

Fraunhofer Institute for Solar Energy Systems ISE researchers have examined the question of which silicon bottom cell will be most suitable for use in tandem cells. The team evaluated multiple silicon cell concepts based on both cost and efficiency in serving as the bottom layer in a perovskite-silicon tandem cell.

Investigated perovskite silicon tandem concepts featuring four different silicon bottom cells (P E RC, TOPerc, TOPCon2, and SHJ) and two different interconnection concepts (ReCO and SiT). Image from article

The study, based on both simulation and experimental work, details advantages to various approaches with the silicon cell and concludes that in almost every case, perovskite-silicon tandem cells have the potential to bring solar costs down below what could be achieved with silicon alone.

Sweden-based perovskite-based PV start-up Evolar has announced an investment from Norwegian renewables investor Magnora as it targets rapid commercialization of its technology.

Evolar has been researching the development of perovskites in solar cells, and Evolar now intends to help commercialize the technology. Evolar's approach is to add a perovskite-based thin-film layer to cells to create a tandem solar cell, which the company said is expected to increase module efficiency by five percentage points.