Technical / research - Page 25

Researchers at Empa, National University of Singapore (NUS) and Helmholtz Institute Erlangen-Nürnberg for Renewable Energy HI ERN have reported novel electrical and optical enhancement approaches to maximize the performance of perovskite front cells. 

The team introduced new electrical and optical techniques, using methyldiammonium diiodide and adjusting the optical interference spectrum. This resulted in a record efficiency of 20.2% (21.8% by J-V scan) for a semi-transparent perovskite cell and 81.5% average near-infrared transmittance. 

Researchers at Graphenea, University of Utah and Kairos Sensors have examined a perovskite-based graphene field effect transistor (P-GFET) device for X-ray detection.

The device architecture consisted of a commercially available GFET-S20 chip, produced by Graphenea, with a layer of methylammonium lead iodide (MAPbI₃) perovskite spin coated onto the top of it. This device was exposed to the field of a molybdenum target X-ray tube with beam settings between 20 and 60 kVp (X-ray tube voltage) and 30–300 μA (X-ray tube current). Dose measurements were taken with an ion-chamber and thermo-luminescent dosimeters and used to determine the sensitivity of the device as a function of the X-ray tube voltage and current, as well as source-drain voltage.

Researchers from the University of Rome Tor Vergata, ENEA and CNR-ISM have used protective buffer layers in perovskite solar cells to mitigate damage during the sputtering of indium tin oxide in the production process. The scientists claim the buffer layers were able to achieve this without damaging the cell’s average visible transmittance.

The cell utilizes buffer layers made of transition metal oxides (TMOs) intended to protect the cell during the sputtering of indium tin oxide (ITO) in the cell production process. The scientists tested, in particular, two different evaporated transition metal oxides (TMOs) – molybdenum oxide (MoO_x) and vanadium oxide (V₂O_x)  and found the former provided the best performance.

In an effort to tackle the challenge of perovskite solar cells' thermal instability, researchers at City University of Hong Kong (CityU), National Renewable Energy Laboratory (NREL) and Huazhong University of Science and Technology have developed a unique type of self-assembled monolayer, or SAM for short, and anchored it on a nickel oxide nanoparticles surface as a charge extraction layer. This method dramatically enhanced the thermal robustness of perovskite solar cells, according to Professor Zhu Zonglong of the Department of Chemistry at CityU.

“By introducing a thermally robust charge extraction layer, our improved cells retain over 90% of their efficiency, boasting an impressive efficiency rate of 25.6%, even after operated under high temperatures, around (65℃) for over 1,000 hours. This is a milestone achievement,” said Professor Zhu.

Researchers at the University of North Carolina at Chapel Hill and Arizona State University and have designed a large-area perovskite-silicon tandem solar cell that achieved a steady-state power conversion efficiency of 25.1% for tandem devices with a large aperture area of 24 cm².

The team set out to overcome shunting, which is a common issue when scaling up perovskite solar technologies from small-area cells to large-area devices. “Shunts” in PV cells create alternate pathways for a solar-generated charge, leading to power losses. Reduced shunt resistance is associated with multiple forms of module degradation and failure, including hotspots and potential-induced degradation.

A group of scientists from Germany's Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE), with support from Oxford PV Germany, have examined shingling as an interconnection method for perovskite-silicon tandem (PVST) cells.

Full-format perovskite-silicon tandem shingle modules produced at Fraunhofer ISE in collaboration with Oxford PV. Image from Solar Energy Materials and Solar Cells.

The scientists explained that the combination of PVST cells with shingling allows boosting the module efficiency even further due to the increase of the photoactive area through the absence of cell gaps. They went on to say that shingling suits the temperature limitations of the PVST cells since the main factor for the choice of the processing temperature is the curing conditions of the electrically conductive adhesive.

Existing fabrication processes for creating efficient metal halide perovskite solar cells (PSCs) require an inert (i.e., chemically inactive) atmosphere, such as that within a nitrogen glovebox. Recently, researchers from China's North China Electric Power University have introduced a strategy to create PSCs with PCEs above 25% in ambient air. 

This strategy is hoped to accelerate commercialization of PSCs. "The fabrication of perovskite solar cells (PSCs) in ambient air can accelerate their industrialization," Luyao Yan, Hao Huang and their colleagues wrote in their paper. "However, moisture induces severe decomposition of the perovskite layer, limiting the device efficiency. We show that sites near vacancy defects absorb water molecules and trigger the hydration of the perovskite, eventually leading to the degradation of the material." To fabricate their solar cells in ambient air conditions, the scientists blocked the pathway through which perovskite layers can become hydrated and consequently suffer severe damage. They did this using the acetate salt form of the chemical compound guanabenz, known as GBA.

Researchers from the University of Warsaw and the Fraunhofer Institute for Solar Energy Systems ISE have examined the question of whether or not nano-scale surface texturing, used on some silicon cells, can be applied to perovskite cells instead of more commonly used planar magnesium fluoride anti-reflection coatings.   

a) the scheme of the perovskite solar cell sample before any top surface modification and after the application of either MgF2 layer or honeycomb texture application, b) device photography with four active cell areas after imprinting the honeycomb texture. Image from Advanced Materials and Interfaces

“To minimize losses, silicon cells are typically etched with corrosive chemical agents, a process that creates microscopic pyramid pattern on the surface, effectively reducing reflection,” said the scientists. “Unfortunately, perovskites are sensitive to many chemical substances, which is why less effective planar anti-reflective coatings [planar MgF₂] applied through less-invasive sputtering have been employed so far.”

Toray Research Centre (TRC) has been developing cutting-edge perovskite solar cells analysis services since 2014. The company can perform a wide range of measurements and tests, on a wide range of perovskite panel types, without atmospheric exposure, at the company’s state-of-the-art facilities.

TRC’s highly skilled technical team recently published five technical white papers, each showcasing perovskite analysis results. 

• Evaluation of electrical characteristics and crystalline in perovskite solar cells: TRC evaluated to surface roughness and the distribution of spreading resistance near the surface by SSRM. The result showed that the regions of high spreading resistance on the surface of the PVK layer increase with heat treatment. TRC also performed ACOM-TEM analysis and it revealed a decrease in PVK phase and particle size, and an increase in PhI2 phase with heat treatment.
• Surface analysis of power generation layer for Perovskite Solar Cells: X-ray diffraction (XRD), SEM (Secondary Electron Microscopy), and SSRM (Scanning Spread Resistance Microscopy) can evaluate the crystal structure, the form of the surface, the distribution of element, and spread resistance.
• Evolved gas analysis by TPD-MS and depth profile analysis by SIMS of perovskite solar cells: To improve the heat treatment during the perovskite solar panel production process, it is important to understand the decomposed gases from the material and the composition distribution in the material. In this paper, TRC shows the evaluation results of evolved gases during heating by TPD-MS and the elemental distribution in the depth direction by GCIB-TOF-SIMS and Dynamic-SIMS
• Depth profile analysis to element and organic matter of Perovskite Solar Cell: Cross-sectional TEM, Dynamic-SIMS(D-SIMS) and GCIB-TOF-SIMS can be performed the distribution of element and organic matter with high spatial resolution and high sensitivity under non-exposed atmospheres. These processes are very helpful for the improvement of process, materials and devices of PSC
• Composition and impurity analysis of light absorbers of perovskite-based solar cells: It is important to figure out the concentration of composition and impurity of light absorbers to achieve high efficiency in perovskite-based solar cells. For the analysis of inorganic elements, ICP-AES, ICP-MS and ion chromatography are available.

TRC offers its unique and high-quality analysis services to perovskite solar panel developers and producers - click here to inquire about TRC's services. TRC’s analysis services can assist in finding process flaws, increase device performance and accelerate R&D efforts.

Researchers from Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley have developed room-temperature-solution (20 °C) and low-temperature-solution (80 °C) synthesis procedures for a new class of metal halide perovskite high-entropy semiconductor (HES) single crystals. The “multielement ink” could enable cost-effective and energy-efficient semiconductor manufacturing and accelerate the sustainable production of next-gen microelectronics, photovoltaics, solid state lighting, and display devices.

“The traditional way of making semiconductor devices is energy-intensive and one of the major sources of carbon emissions,” said Peidong Yang, the senior author on the study, a faculty senior scientist in Berkeley Lab’s Materials Sciences Division and professor of chemistry and materials science and engineering at UC Berkeley. “Our new method of making semiconductors could pave the way for a more sustainable semiconductor industry.”