Technical / research - Page 23

Researchers at China's Wuhan University of Technology, Huazhong University of Science and Technology and Jinan Municipal Bureau of Industry and Information Technology have developed a novel playdough-like graphite putty as top electrode for perovskite solar devices. The electrode is malleable and so can form good contact with the hole-transporting layer and the conductive substrate at room temperature using a simple pressing technique, which facilitates the fabrication of both small-area devices and perovskite solar modules. 

Carbon-based perovskite solar cells (C-PSCs) are promising candidates for large-scale photovoltaic applications due to their theoretical low cost and high stability. However, the fabrication of high-performance C-PSCs with large-area electrodes remains challenging. In their recent research, the team showed that corresponding small devices and modules can achieve efficiencies of 20.29% (∼0.15 cm²) and 16.01% (∼10 cm²), respectively. Moreover, they analyzed the limitations of the optical and electrical properties of this playdough-like graphite electrode on the device performance, suggesting a direction for further improvement of C-PSCs in the future.

It was reported that researchers at the Institute for Advanced Materials at the Universitat Jaume I in Castelló have created a method for synthesizing organic-inorganic tin halide perovskites and generating thin films or coatings from them, which, when deposited on substrates, have optoelectronic properties that are useful for the creation of devices such as perovskite-based LEDs (PeLEDs).

The method developed by the team consisting of Dr. Samrat Das Adhikari and the doctoral student, Jesús A. Sánchez Diaz, and led by the researcher Iván Mora Seró, exhibits excellent photoluminescence and stability properties that are suitable for commercial application in the field of optoelectronic devices (solar cells, LEDs, etc.).

A team of researchers, led by Nuri Yazdani, Vanessa Wood at ETH Zurich, and Aaron Lindenberg at Stanford, along with colleagues at Empa, recently studied atom motion within nanocrystals with a time resolution in the range of billionths of a second. 

The scientists managed to capture snapshots of the crystal structure of perovskite nanocrystals as excited electrons deformed it. They surprisingly found that the deformation straightened out the skewed crystal structure rather than making it more disordered.

Researchers at Germany’s Fraunhofer ISE have estimated that the practical power conversion efficiency potential of perovskite-silicon tandem solar cells may reach up to 39.5%. In a recent study, the Fraunhofer ISE scientists set out to provide guidelines for future research on perovskite-silicon tandem solar cells by identifying the most significant loss mechanisms at the perovskite/ETL interface, in the series resistance, and in light management.

The team explained that the calculated practical efficiency potential of 39.5% for a perovskite silicon tandem device under standard measurement conditions (STC) can serve as an input for future studies which are required for a better understanding of the full system before the commercialization of tandem solar cell technology can take place.

Researchers in Sweden and China have studied the reasons behind the short operational lifetime of blue perovskite-based LEDs (PeLEDs). 

While perovskite light-emitting diodes (PeLEDs) have seen unprecedented development in device efficiency over the past decade, they still suffer from poor operational stability. This is especially true for blue PeLEDs, whose operational lifetime remains orders of magnitude behind their green and red counterparts. The scientists in this work have systematically investigated this efficiency-stability discrepancy in a series of green- to blue-emitting PeLEDs based on mixed Br/Cl-perovskites. Typically, mixed chloride/bromide perovskites are employed to produce ideal blue emission. However, the researchers have uncovered a counterintuitive fact: even minute quantities of chloride loading can have a dramatic negative impact on the operational lifetime of these devices. 

Researchers from AMOLF have used perovskite semiconductors to develop a simple spray test to detect the presence of lead. A lead-containing surface shines bright green when it is sprayed with the test, which is said to be a 1,000 times more sensitive than existing tests and the researchers found no false positive or false negative results. 

"We have hijacked the technology of perovskite semiconductors and used it in a widely deployable lead test. Nobody in this discipline had ever thought of that," says Lukas Helmbrecht, researcher at the group Self-Organizing Matter led by Wim Noorduin at AMOLF. "We are very pleased with these results," says Noorduin. "It is a really cool project and it is quite rare for fundamental research to literally impact the entire world with an application."

Researchers from the Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM), Germany's University of Potsdam and The Chinese University of Hong Kong have addressed an important aspect in the field of perovskite solar cells (PSCs) – the exact role of excess lead iodide content within the perovskite layer. While an optimal amount of excess lead iodide contributes to improved grain boundary passivation and blocking of minority charge carriers, leading to the development of highly efficient PSCs, the photo-stability of PSCs with surplus lead iodide remains a major concern. This concern stems from the catalytic role excess lead iodide can play in the degradation of PSCs under illumination.

The issue often arises during the fabrication of perovskite films using a two-step spin coating method, where the conversion of lead iodide films to perovskite is hindered due to challenges in controlling the reaction between lead iodide films and cationic precursor solutions. Various modifications of the two-step approach are presented in the literature, each aiming to achieve a near full conversion of lead iodide films into perovskite when exposed to cationic precursor solutions.

Researchers of Karlsruhe Institute of Technology (KIT) and of two Helmholtz platforms—Helmholtz Imaging at the German Cancer Research Center (DKFZ) and Helmholtz AI—have found a way to predict the quality of the perovskite layers and consequently that of the resulting solar cells. Using machine learning and new methods in artificial intelligence (AI), it is possible to assess their quality from variations in light emission already in the manufacturing process.

"Manufacturing these high-grade, multi-crystalline thin layers without any deficiencies or holes using low-cost and scalable methods is one of the biggest challenges," says tenure-track professor Ulrich W. Paetzold who conducts research at the Institute of Microstructure Technology and the Light Technology Institute of KIT.

Tokyo Institute of Technology researchers have shown that donor doping into a mother material with disordered intrinsic oxygen vacancies, instead of the widely used strategy of acceptor doping into a material without oxygen vacancies, can greatly enhance the conductivity and stability of perovskite-type proton conductors at intermediate and low temperatures of 250–400 ℃, (e.g. 10 mS/cm at 320 ℃). This approach provides a new design direction for proton conductors for fuel cells and electrolysis cells.

Protonic ceramic (or proton conducting) fuel/electrolysis cells (PCFCs/PCECs) are a strong contender for future sustainable energy technologies. These devices can directly convert chemical energy into electricity and vice versa with zero emissions at low or intermediate temperatures, making them an attractive option for many emerging applications such as next-generation distributed power sources. In addition, unlike other types of fuel cells and electrolysers, the PCFCs/PCECs do not require precious metal catalysts or expensive, heat-resistant alloys.

Researchers at Northwestern University and University of Toronto have developed a way to improve the efficiency of inverted perovskite solar cell using a combination of molecules to address different issues. They reported a dual-molecule solution to overcoming losses in efficiency as sunlight is converted to energy. 

By incorporating a molecule to address surface recombination, in which electrons are lost when they are trapped by defects — missing atoms on the surface, with a second molecule to disrupt recombination at the interface between layers, the team achieved a National Renewable Energy Lab (NREL) certified efficiency of 25.1% where earlier approaches reached efficiencies of just 24.09%.