Efficiency - Page 30

Researchers at the Karlsruhe Institute of Technology (KIT) in Germany have fabricated a spin-coated, two-terminal, all-perovskite tandem solar module with an aperture area of 12.25 square centimeters and a geometric fill factor of 94.7%. The team said that laser-scribed two-terminal all-perovskite tandem (2TPT) solar cells have attracted attention in recent years, as they combine a wide bandgap perovskite top subcell with a narrow-bandgap perovskite bottom subcell.

The scientists used a 23-5% efficient 2TPT solar cell based on perovskite and copper/indium/selenium (CIS) thin-film, which they first announced in June. It has an open-circuit voltage of 1.59 V, a short-circuit current of 19.4 mA cm–2, and a fill factor of 75.5%.

Researchers from the Swiss Center for Electronics and Microtechnology (CSEM) and the École polytechnique fédérale de Lausanne (EPFL) have reported a power conversion efficiency exceeding 30% for a 1 cm² tandem perovskite-silicon solar cell, which represents a world record for a PV device of this kind. The team achieved an efficiency of 30.93% for a 1 cm² solar cell based on high-quality perovskite layers from solution on a planarized silicon surface and an efficiency of 31.25% on a cell of the same size and fabricated with a hybrid vapor/solution processing technique compatible with a textured silicon surface.

“These results constitute two new world records: one for the planar and one for the textured device architecture,” the researchers explained, noting that both efficiencies were certified by the US Department of Energy's National Renewable Energy Laboratory (NREL). “The latter approach provides a higher current and is compatible with the structure of current industrial silicon solar cells”. Unfortunately, the researchers did not disclose technical details on how they improved the efficiency of both devices.

A research group that includes scientists from Chinese module manufacturer JinkoSolar, Australian National University, the Beijing Institute of Technology and Peking University has developed a monolithic perovskite-silicon n-type tandem solar cell based on tunnel oxide passivated contacts (TOPCon) tech for the bottom cell.

“We fabricate the perovskite sub-cell conformally on the damage-etched front surface to mitigate the negative impacts of rough c-Si substrates, thus preventing shunt paths across carrier transport layers, absorber layers, and their interfaces in relevance,” the scientists said, noting that they followed a standard wafering and etching process that is commonly used in the PV industry.

Tokyo Chemical Industry (TCI) is a global supplier of laboratory chemicals and specialty materials. TCI is a leading the next-generation solar technology industry by providing high-quality and reliable materials, including metal halide perovskite precursors such as lead/tin halides and organic onium salts, as well as carrier transporting materials.

TCI recently launched hole selective self-assemble monolayer (SAM) forming agents, 2PACz [Product Number: C3663] , MeO-2PACz [Product Number: D5798] and Me-4PACz [Product Number: M3359] for high performance perovskite solar cells. The company is getting ready to launch some more related materials in 2022. We thought it'd be a good time to catch up with TCI, and have conducted a Q&A with TCI’s Institute for Material Science's general manager, Dr. Taro Tanabe.

Researchers at King Abdullah University of Science and Technology (KAUST) and Max Planck Institute have developed an inverted perovskite-silicon tandem solar cell with a 1 nm thick interlayer based on magnesium fluoride (MgFx) placed between the perovskite layer and the hole transport layer (HTL), in order to reduce voltage losses while still retaining 95.4% of its initial efficiency after 1,000 hours.

The scientists stated that the charge transport and recombination interfaces could be carefully tuned with MgFx interlayers, enabling a certified efficiency of 29.3%. Currently, the record perovskite/silicon tandem solar cell is a 29.8% device that was recently developed by scientists at Helmholtz-Zentrum Berlin (HZB) in Germany. The scientists fabricated the new cell with a sub-cell based on crystalline silicon wafers with double-side texture, which they say reduces front reflection while improving light trapping. They also placed the MgFx interlayer at the electron-selective top contact.

The CEA at INES has reported the design of flexible perovskite solar modules with a surface area of 11.6 cm² and a power conversion efficiency of 18.9% (stabilized efficiency > 18.5%). This performance is said to be a world record for flexible perovskite modules over 10 cm².

Perovskite-based modules before and after flexible encapsulation. Image credit: CEA

For some applications, the use of flexible substrates may be attractive for single-junction perovskite technology as it opens the way to high-speed, low-temperature printing processes. Thus, it becomes possible to use low cost substrates whereas inorganic flexible technologies, such as CIGS, require higher temperature processes and substrates that are more expensive. Many teams around the world are trying to meet the challenges of making larger area devices with sufficient stability for real-life applications. This is one of the tasks standing before partners of the European APOLO project, as part of which these results were obtained.

Researchers from Wuhan University and Shenzhen University in China have designed a four-junction tandem (4T) solar cell based on perovskite and copper, indium, gallium and selenium (CIGS), through a novel surface passivation technique that uses guanidine bromide (GABr).

The team tested GABr in mixed solvents combining isopropyl alcohol (IPA) and toluene (TL), which they said can efficiently passivate interface and grain boundary defects by minimizing the IPA solubility of the perovskite surface. They compared the mixing of IPA with ethyl acetate (EA), chlorobenzene (CB), and toluene (TL) to dissolve GABr, and further optimized the concentration of GABr and the mixing ratio of the two solvents.

Researchers from Princeton University in the U.S and Sweden's Linköping University have reported the development of "the first perovskite solar cell with a commercially viable lifetime". The team estimates their device can perform above industry standards for around 30 years, far more than the 20 years used as a threshold for viability for solar cells.

Not only is the device said to be highly durable, but it also meets common efficiency standards. It is the first of its kind to rival the performance of silicon-based cells, which have been market leaders for decades. 

Researchers taking part in the EU project PERCISTAND, among them ones from the Karlsruhe Institute of Technology (KIT) and TNO, have developed perovskite/CIS tandem solar cells with an efficiency of almost 25% – the highest for this technology to date.

In addition, this combination of materials reportedly ensures lightness and versatility, so that the use of these tandem solar cells on vehicles, portable devices and foldable or rollable devices is also conceivable. 

Scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL), CU-Boulder and the University of Toledo have demonstrated a tin-lead perovskite cell that overcomes problems with stability and improves efficiency. The new cell, a tandem design with two layers of perovskites, reached 25.5% efficiency.

The new cell also retained 80% of its maximum efficiency after 1,500 hours of continuous operation, or more than 62 days.