Efficiency - Page 27

Researchers from Empa, EPFL, Sichuan University, Jiaxing University, Soochow University, University of Cologne, University of Potsdam, HZB and the University of Oxford have developed a flexible all-perovskite tandem solar cell with a mitigated open-circuit voltage deficit and reduced voltage loss. The team reported flexible tandem efficiency of almost 24% on small area cells using the spin coating method.

Flexible all-perovskite tandem cells are currently less developed than rigid cells, due to a difficult deposition process for the cell's functional layers and a lower open-circuit voltage. This is due to high defect densities within the perovskite absorber layer and at the perovskite/charge selective layer interface.

Researchers from Ulsan National Institute of Science and Technology (UNIST), Wuhan University of Technology and Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory have manufactured high efficiency, stable, and scalable perovskite solar cells (PSCs) via vacuum deposition, a method of fabricating organic light-emitting display devices (OLEDs). 

In their study, the research team demonstrated efficient and stable PSCs with a vacuum-processed Ruddlesden-Popper (RP) phase perovskite passivation layer. By controlling the deposition rate of the RP phase perovskite, which directly influenced its crystallographic orientation, the research team successfully obtained a highly ordered 2D perovskite passivation layer.

Chinese perovskite solar PV company Wuxi UtmoLight Technology recently achieved 18.2% power conversion efficiency for an in-house developed large-scale perovskite solar module with an area of 756 cm², as reports suggest.

UtmoLight refers to this as a breakthrough in large size perovskite module technology after having reported the same 18.2% efficiency for a smaller size module with 300 cm² dimension in the past. This shows the module can maintain a high conversion efficiency despite the enlargement of the module area. Mass production of this technology is now becoming mature, it added.

Researchers from Zhejiang Energy Group R&D and the Chinese Academy of Sciences (CAS) have reported what they say is "the first monolithic perovskite/silicon tandem featuring an industrially applicable front-side-nanostructured black silicon with a tunnel oxide passivated contact (TOPCon)".

The TOPCon together with the surface reconstruction of black silicon contributes to the high-level surface passivation without sacrificing the broadband light trapping. Additionally, the reconstructed nanotexture significantly facilitates the wetting of perovskite and acts as a nanoconfining scaffold to guide the vertical growth of perovskite.

Researchers from Peking University, China Automotive Technology and Research Center, Beijing Institute of Technology and Jiangnan University recently demonstrated the ability of tuning the Fermi level of the hole transport layer (HTL) to reduce the energy level difference (Schottky barrier) between HTLs and Cu. In addition, the team identified that the balance of energy level difference between HTL and adjacent layers (including perovskite and Cu) is crucial to efficient carrier transportation and photovoltaic performance improvement in the PSCs.

The team's effort was aimed at addressing the challenge of developing low-cost and stable metal electrodes, which could be very important for mass production of perovskite solar cells (PSCs). As an earth-abundant element, Cu becomes an alternative candidate to replace noble metal electrodes such as Au and Ag, due to its comparable physiochemical properties with simultaneously good stability and low cost. However, the undesirable band alignment associated with the device architecture impedes the exploration of efficient Cu-based n-i-p PSCs.

Solliance partners TNO, TU Eindhoven, imec and TU Delft have joined forces to further push the conversion efficiency of tandem solar cells to beyond the limits of today’s commercial PV modules. They have achieved an extraordinary feat: the first time that four-terminal perovskite/silicon tandem devices with certified top cell passed the barrier of 30%.

Bottom silicon solar cell and top perovskite solar cell with transparent contacts. Photo credit: Niels van Loon

Such high efficiency enables more power per square meters and less cost per kWh. The result was presented during the 8th World Conference on Photovoltaic Energy Conversion (WCPEC-8) in Milan and has been achieved by combining perovskite solar cell tech with conventional silicon solar cell technologies. The perovskite cell that features transparent contacts and is part of the tandem stack has been independently certified.

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.

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%.