Technical / research - Page 34

Researchers at the University of California, Davis College of Engineering and Georgia Institute of Technology are using machine learning to identify new materials for high-efficiency solar cells. Using high-throughput experiments and machine learning-based algorithms, they have found it is possible to forecast the materials’ dynamic behavior with very high accuracy, without the need to perform as many experiments.

A primary challenge in the field of perovskite-based solar cells is that the perovskite devices tend to degrade faster than silicon when exposed to moisture, oxygen, light, heat, and voltage. The challenge is to find which perovskites combine high-efficiency performance with resilience to environmental conditions. Marina Leite, associate professor of materials science and engineering at UC Davis and senior author of the paper, said that “the number of possible chemical combinations alone is enormous". Furthermore, they need to be assessed against multiple environmental conditions, alone and in combination, which results in a hyperparameter space that cannot be explored using conventional trial-and-error methods. “The chemical parameter space is enormous,” Leite said. “To test them all would be very time consuming and tedious.”

Scientists from Karlsruhe Institute of Technology (KIT) have developed a new way to fabricate micro-patterned translucent perovskite solar cells that could be used in tandem solar modules intended for applications in building-integrated photovoltaics (BIPV). “While translucent perovskite multi-junction devices have been envisaged and recognized as a promising path towards high- efficiency neutral-color transparent PV, the tolerance of complex perovskite tandem stacks against extensive laser scribing has yet to be explored,” the research group said.

The researchers noted that the cells have thus far provided decent levels of power conversion efficiency while maintaining a high average visible transmittance (AVT). They used a custom-built laser scribing setup to fabricate a perovskite solar cell with n–i–p architecture and with an active area of 0.105 cm². The device is based on an indium tin oxide (ITO) substrate, a hole transport layer made of carbazole (2PACz), an electron transport layer made of buckminsterfullerene (C60), an absorber based on methylammonium lead triiodide (CH3NH3PbI3), a bathocuproine (BCP) buffer layer, and a gold (Au) metal contact.

Researchers from Tohoku University and Tokyo Institute of Technology (Tokyo Tech) have proposed a simple sol–gel method for the synthesis of highly pure bifunctional solid acid−base catalysts of perovskite-type oxides.

The rationale for selecting perovskite-type oxides was explained by Professor Keigo Kamata from Tokyo Institute of Technology: “Perovskite-type oxides are gaining importance in several fields, including magneticity, ferroelectricity, piezoelectricity, and catalysis. Moreover, the structure and physiochemical properties of perovskite-type oxides can be tuned by controlling their chemical composition.”

Perovskite solar films developed by a graduate student in the Department of Physics at UC Merced while on an internship at NASA Glenn Research Center (GRC) not only survived 10 months in space with minimal degradation, but the little damage they did incur was more than 90% reversible. 

The research team, that included scientists from UC Merced and Universities Space Research Association (National Aeronautics and Space Administration), National Renewable Energy Laboratory (NREL) and Wilberforce University, have published the results of the first long-term study of perovskite solar samples in space.

Researchers from Pennsylvania State University have developed a narrowband (NB) imaging sensor combining R/G/B perovskite NB sensor array (mimicking the R/G/B photoreceptors in the eye) with a neuromorphic algorithm (mimicking the intermediate neural network of the human visual system) for high-fidelity panchromatic imaging.

A photo of a perovskite NB PD array made in this work. Image from study

Compared to commercial sensors, the team used perovskite “intrinsic” NB photodetectors to exempt the complex optical filter array. In addition, They used an asymmetric device configuration to collect photocurrent without external bias, enabling a power-free photodetection feature. These results presented a promising design for efficient and intelligent panchromatic imaging.

A research team, led by Prof. GUO Xin and Prof. LI Can from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), has unveiled the origin of the stability of Dion–Jacobson (DJ) phase two-dimensional (2D) perovskite materials.

Compared to traditional 3D perovskites with intrinsically low stability, 2D perovskites including the Ruddlesden–Popper (RP) phase and DJ phase are considered attractive due to their enhanced stability, especially DJ 2D perovskites based on organic diammonium cations and inorganic lead iodide octahedra, which have higher structural stability than RP ones. However, some of DJ 2D perovskites are not robust and degrade even more easily than their RP 2D counterparts, which has led to a debate over their stability. These contradictory research results have impelled scientists to search for better understanding regarding the stability mechanism of DJ 2D perovskites with different diammonium cations.

Scientists from Turkey's Konya Technical University have shown that sepiolite, a naturally occurring clay substance, can be added to perovskite precursor materials, and form a scaffold layer that can improve the efficiency and stability of solar cells. The scientists believe that this substance could be valuable in developing reproducible processes for the production of large-area perovskite solar cells.

SEM image of aerosol coated sepiolite films on FTO glasses obtained from 1 mg/ml dispersion in water. (a) 30KX and (b) 50KX magnification. Image from study

The team found that sepiolite, a naturally occurring clay mineral largely composed of silicon, magnesium and oxygen, has a very high active surface area and can easily be dispersed in solvents. It can be used without any alterations as a scaffold layer in a perovskite solar cell. The group worked with planar perovskite solar cells with an initial maximum efficiency of 7.92%, and found that cells fabricated with the sepiolite additive jumped to a maximum efficiency just over 16%, more than a 50% increase for cells produced under otherwise identical conditions.

University of North Carolina at Chapel Hill researchers have demonstrated that self-powered polycrystalline perovskite photodetectors can rival the commercial silicon photomultipliers (SiPMs) for photon counting. 

The new type of photon counting detector could have applications in consumer electronics, sensors, optical communication, radiation detection, and more. It could also offer safer medical imaging and enhance nighttime photography. The team's recent work could open up various new applications of photon counting for perovskites that use their unique defect properties. Compared to current technologies on the market, the team’s technology is reportedly more cost effective and does not require external power sources, broadening the scope of how the technology can be applied

Researchers from Monash University, University of Illinois at Chicago, University of Cambridge and CSIRO Manufacturing have used solution-processed, printable diodes based on perovskite thin films to make a printable, multi-energy X-Ray detector with significantly enhanced flexibility and sensitivity.

Schematic depiction of the fabrication process of an X-ray diode on flexible substrates using a custom-made slot die set up on a commercial R2R coater. 

Silicon and selenium X-ray detectors are the most common for multi-energy X-ray detection. however, these tend to present poor energy discrimination across the broad X-ray spectrum and exhibit limited spatial resolution due to the high thicknesses required for radiation attenuation. In this recent work, the new technology for the X-ray detector is able to overcome these challenges.

Researchers from the University of Toronto in Canada, Northwestern University, The University of Toledo and University of North Carolina at Chapel Hill in the United States, King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, Yunnan University in China, Ecole Polytechnique Fedérale de Lausanne (EPFL) in Switzerland and University of Warwick in the UK have developed a triple-junction perovskite solar cell with a record efficiency of 24.3% with an open-circuity voltage of 3.21 V. 

The NREL has certified the cell’s quasi-steady-state efficiency as 23.3%, which the team stated is the first reported certified efficiency for perovskite-based triple-junction solar cells. They added that triple-junction perovskite solar cells have so far demonstrated a maximum efficiency of around 20%.