Technical / research - Page 44

Researchers from Rice University, Northwestern University, Purdue University, University of Washington, CNRS and Argonne National Laboratory have addressed a long-standing issue in making stable, efficient solar panels out of halide perovskites. It took finding the right solvent design to apply a 2D top layer of desired composition and thickness without destroying the 3D bottom one (or vice versa). Such a cell would turn more sunlight into electricity than either layer on its own, with better stability.

The team, led by Chemical and biomolecular engineer Aditya Mohite and his lab at Rice’s George R. Brown School of Engineering, recently reported their success at building thin 3D/2D solar cells that deliver a power conversion efficiency of 24.5%.

Researchers from Korea University and Seoul Women's University have developed an inverted perovskite solar cell by introducing an electron-accepting interlayer at the interface between the perovskite layer and the electron transport layer.

The solar cell has a p-i-n structure (the perovskite cell material is deposited onto the hole transport layer and then coated with the electron transport layer), which is the opposite of the conventional n-i-p device structure. Inverted perovskite solar cells tend to show good stability, but lack in terms of conversion efficiency and cell performance.

Researchers at University of North Carolina at Chapell Hill and University of Rochester have developed a novel hot gas-assisted method that could improve the fabrication of narrow bandgap (NBG) perovskite films for tandem solar cells. This strategy, combined with an anti-oxidation material added in the film, could increase the solar cells' carrier recombination lifetime (i.e., the time it takes for excess charge carriers to decay).

The researchers explained that all-perovskite tandem perovskite solar cells have the potential to reduce the cost of photovoltaic systems, due to their potential to reach a higher efficiency than their single-junction counterparts, while maintaining the solution fabrication processes. They said that compared to single junction perovskite modules, the application of tandem structures, which have much smaller photocurrents but higher photovoltage, can also reduce the cell-to-module efficiency derate and enable the realization of higher module efficiencies for monolithically interconnected modules in a series.

Researchers at CSIRO and Monash University have reported a flexible perovskite solar cell manufactured using roll-to-roll compatible “printing” type processes, which could potentially be used in large-scale manufacturing. To achieve this, the team developed a viable roll-to-roll process to deposit the electrode layer, which has thus far been a major challenge. The team managed to fabricated cells which achieved a maximum efficiency of 16.7%.

Photo: Hasitha Weerasinghe/CSIRO

Roll-to-roll processes signify a potential for low-cost manufacturing of flexible perovskites. However, adding the electrode layer in a process compatible with the roll-to-roll setup has proven to be a challenge. The research team in this recent work set out to address this issue and develop a process that could allow the electrode layer to be deposited without the need for solvents or heat treatments that potentially damage the perovskite layer as well.

Scientists from China's Jinan University, CoreTech Integrated Limited and Chinese Academy of Sciences have used selective nanosecond-pulse, laser-induced ablation to create a perovskite solar module with a reduced heat-affected zone.

The team showed that a nanosecond pulse laser can deliver a reduced heat-affected zone due to the small thermal diffusion coefficient (Dt) of the perovskite material, contributing to the accomplishment of a high geometric filling factor  (GFF) of up to 95.5%. In addition, the monolithic interconnection quality was improved by finely lifting off the capping layers on indium tin oxide and identifying the residue within the scribed area. As a result, a certified aperture area efficiency of 21.07% under standard 100 mW cm⁻² AM1.5G illumination was achieved with a high photovoltaic fill factor exceeding 80%.

A research team, led by Prof. Wu Kaifeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Dr. Peter C. Sercel from the Center for Hybrid Organic Inorganic Semiconductors for Energy, recently reported the utilization of lattice distortion in lead halide perovskite quantum dots (QDs) to control their exciton fine structure.

Shape or crystal anisotropy in QDs results in energy splitting of their optically bright excitons (bound electron-hole pairs), known as fine structure splitting (FSS). For example, the excitons' FSS can be exploited for coherent control of quantum states for quantum computing, or for polarization-entangled photon-pairs in quantum optics, although for the latter it is important to suppress the magnitude of splitting. Studying FSS usually requires single or just a few QDs at liquid-helium temperature, due to its sensitivity to QD size and shape. Measuring FSS at an ensemble-level, much less controlling it, seems impossible unless all the dots are made to be nearly identical.

A team of researchers from China's Tsinghua University, National Center for Nanoscience and Technology and Switzerland's Institute of Computational Physics (ICP) of the ZHAW School of Engineering have proposed a strategy to reduce defects and microstrains in perovskite films through multifunctional additives, achieving a record PCE of 23.6% for single-junction flexible perovskite solar cells (FPSCs).

Flexible perovskite solar cells (FPSCs) prepared on flexible substrates, which possess excellent flexibility and a high power-to-weight ratio, hold promise as a power source for wearable electronic devices, aerospace, and building integrated photovoltaics (BIPVs). Further improving the power conversion efficiency (PCE) and bending resistance of flexible devices is key to promoting their practical application.

Scientists from King Abdullah University of Science and Technology (KAUST) and Solar Energy Research Institute of Singapore (SERIS) have examined the potential-induced degradation (PID) susceptibility of perovskite-silicon tandem devices fabricated in their lab. They exposed tandem cell devices to PID stress and found that they lost as much as 50% of their initial performance after just one day. This led the team to assess that more work needs to be done on the issue before perovskites can be commercialized and deployed at scale.

Research on perovskite solar cells' stability challenges has largely focused on the material’s sensitivity to moisture, high temperatures, and other environmental conditions. Potential-induced degradation (PID), caused by currents leaking from the cell and driving various damaging mechanisms, has long been a threat to performance in silicon PV modules, but has so far been much less explored in emerging PV technologies such as perovskite.

Scientists from Kaunas University of Technology and Vilnius University in Lithuania and University of Colorado in the U.S have proposed a method for increasing the stability and performance of perovskite solar cells. The team synthesized a new class of carbazole-based cross-linkable materials, which are resistant to various environmental effects, including strong solvents used in the production of solar cells.

When applied as hole transporting layers, the new materials helped achieve the 16.9% efficiency of the inverted-architecture perovskite cells at the first attempt. It is expected to reach higher efficiency upon optimization.

An approach called "carbon capture and utilization" dictates that when the production of harmful greenhouse gases cannot be prevented, the goal is to convert them into something useful. This requires special catalysts, which until now encountered the problem of a layer of carbon that quickly forms on these catalysts—this is called "coking"—and the catalyst loses its effect.

Now, a team of scientists at TU Wien developed a new approach to converting harmful gases: tiny metallic nanoparticles were produced on perovskite crystals through special pre-treatment. The interaction between the crystal surface and the nanoparticles then ensures that the desired chemical reaction takes place without the 'coking' effect.