Efficiency - Page 46

KAIST researchers have designed a method to make perovskite crystals at lower temperatures, that could lead the way towards lower-cost solar cells by eliminating defects that reduce efficiency.

Most current work on perovskite solar cells focuses on polycrystalline versions, where the efficiency record is 25%, say Omar Mohammed and Osman Bakr, materials scientists at King Abdullah University of Science and Technology. But polycrystalline films are only a few hundred nm thick, whereas single crystals can be grown to approximately 20 µm. The thicker films can absorb more light so single-crystal solar cells could prove to be superior. The problem is that so far, single-crystal lead perovskite solar cells don't reach 20% efficiency.

Scientists from Hasselt University, imec, VITO, EnergyVille and international partners within the PERCISTAND consortium have announced that they achieved an energy efficiency of 25% with a thin-film solar cell.

Bart Vermang, coordinator within the PERCISTAND consortium, describes the development of thin-film solar cells as 'Pioneering'. The consortium, which partly consists of the collaborations within EnergyVille and Solliance, has succeeded in achieving a record energy efficiency with thin film solar cells. 'We've achieved an energy efficiency of 25 percent for the first time, which is just as much energy as a traditional solar cell can generate on a day-to-day basis. And we haven't yet reached the upper limit of our thin-film solar cells.'

Researchers at the Pohang University of Science & Technology (POSTECH) have developed eco-friendly-solvent processable hole transport polymers by using peppermint oil and walnut aroma food additives and the polymer can prevent lead leakage.

The POSTECH research team consisted of Prof. Taiho Park and Junwoo Lee, that developed Alkoxy-PTEG - hole transport polymers that could be dissolved in peppermint oil, by applying ethylene glycol side chains when producing perovskite solar cells. Also, the team confirmed that this polymer captured leaking lead in aging perovskite solar cells.

Research by EPFL shows that a new engineered passivator, 4'tert'butyl'benzylammonium iodide (tBBAI), has bulky tert'butyl groups that prevent unwanted aggregation by steric repulsion. It was found that simple surface treatment with tBBAI significantly accelerates the charge extraction from the perovskite into the spiro'OMeTAD hole'transporter, while retarding the nonradiative charge carrier recombination.

This boosts the power conversion efficiency (PCE) of the PSC from '20% to 23.5%, reducing the hysteresis to barely detectable levels.

Researchers at Spain's Charles III University of Madrid claim to have significantly reduced optical losses in a monolithic, nano-structured perovskite silicon tandem solar cell by using a new design.

Such two-terminal tandem cell devices are said to offer high conversion efficiency, due to a large number of layers, but to also suffer significant optical losses because of the high number of interfaces.

Hunt Perovskite Technologies (HPT), a Texas-based perovskite applications developer, has reported a milestone in the development of a highly-durable perovskite technology for the manufacture of low-cost printed solar cells.

In December 2019, HPT demonstrated that its ink-based process was able to produce a perovskite solar cell that exceeded key benchmarks recognized by the solar cell manufacturing industry and exceeded the International Electrotechnical Commission (IEC) durability thresholds in temperature, humidity, white light and ultraviolet (UV) stress testing while reaching efficiency performance levels of 18%.

Researchers at Saudi Arabia's King Abdullah University of Science and Technology (KAUST) claim to have improved the performance of solar cells based on inverted perovskites.

That type of cell has a device structure known as 'p-i-n', in which hole-selective contact p is at the bottom of intrinsic perovskite layer i with electron transport layer n at the top. Conventional halide perovskite cells have the same structure but reversed ' a 'n-i-p' layout. In n-i-p architecture, the solar cell is illuminated through the electron-transport layer (ETL) side; in the p-i-n structure, it is illuminated through the hole'transport layer (HTL) surface.

Panasonic Corporation has achieved an energy conversion efficiency of 16.09% for a perovskite solar module (Aperture area 802 cm²: 30 cm long x 30 cm wide x 2 mm thick) by developing lightweight technology using a glass substrate and a large-area coating method based on inkjet printing.

This was carried out as part of the project of the New Energy and Industrial Technology Development Organization (NEDO), which is working on the "Development of Technologies to Reduce Power Generation Costs for High-Performance and High-Reliability Photovoltaic Power Generation" to promote the widespread adoption of solar power generation.

Scientists from Japan's Gifu University and the Tokyo Institute of Technology have identified a chalcogenide perovskite material with light absorption attributes strong enough to offer the potential for a theoretical maximum conversion efficiency of 38.7% in a silicon perovskite tandem solar cell.

The material ' BaZrTiS₃ ' has a light absorption coefficient exceeding 10⁵cm^-1, the highest of all solar cell materials including chalcogenide perovskites such as SrZrS₃, BaHfS₃ and SrHfS₃, the scientists claim.

The groups of Steve Albrecht and Bernd Stannowski at HZB have reached a record efficiency of 29.15% of its tandem solar cell made of perovskite and silicon.

The illustration shows the structure of the tandem solar cell: between the thin perovskite layer (black) and the silicon layer (blue) are functional intermediate layers. © Eike Köhnen/HZB

This value has been officially certified by the CalLab of the Fraunhofer Institute for Solar Energy Systems (ISE) and means that surpassing the 30% efficiency mark is now within reach.