Tandem - Page 22

The following post is a sponsored post by MBRAUN

Prof. Dr. Steve Albrecht and his 11-member team of the Helmholtz Innovation Lab HySPRINT at
Helmholtz-Zentrum Berlin (HZB) develop tandem solar cells that combine the advantages of silicon and perovskite solar cells. In order to create the best research conditions, Prof. Albrecht had installed systems from the market leaders, MBRAUN and CreaPhys (a part of MBRAUN).

HySPRINT Perovskite Lab © HZB / M. Setzpfandt

The Perovskite cluster is composed of 4 different parts: Precursor synthesis, wet coating with spin coater, evaporation of perovskites and metallization, scaling with inkjet printer and slot die coater under laminar flow. Every part of the cluster is integrated in inert gloveboxes under inert atmosphere to guarantee the best performance of the devices, as well as the best repeatability of the processes.

Researchers from HZB, Oxford University, Technical University Berlin and Oxford PV have shown that the infrared reflection losses in tandem cells processed on a flat silicon substrate (such as perovskite/silicon tandem cells) can be significantly reduced by using an optical interlayer, consisting of nanocrystalline silicon oxide. Based on this, the team managed to achieve impressive efficiency and reported that the best tandem device in this work reached a certified conversion efficiency of 25.2%.

a) Cross-section of the simulated monolithic perovskite/SHJ tandem cell (layer thicknesses and morphological features not to scale). b) Cross-sectional SEM image of the top region of the tandem device.

Perovskite/silicon tandem solar cells are attractive for their potential for boosting cell efficiency beyond the crystalline silicon (Si) single-junction limit. However, the relatively large optical refractive index of Si, in comparison to that of transparent conducting oxides and perovskite absorber layers, often results in significant reflection losses at the internal junction between the cells in monolithic (two-terminal) devices. Therefore, light management is crucial for improving photocurrent absorption in the Si bottom cell.

Researchers at Solliance, in collaboration with MiaSole Hi-Tech Corp., have designed a flexible solar cell with an impressive power conversion efficiency of 21.5%. The solar cell combines two thin-film solar cell technologies into a 4 terminal tandem solar cell stack: a top flexible semi-transparent perovskite solar cell with a bottom flexible copper indium gallium selenide (CIGS) cell.

A tandem solar cell, which combines a perovskite and a Cu(In,Ga)Se2 (CIGS) cell, has the potential for high conversion efficiency exceeding single junction solar cell performance thanks to tunable and complementary bandgaps of these individual thin film solar cells. CIGS technology has a proven track record as a high efficiency and stable solar technology, and has entered high volume manufacturing in multi-GW scale around the world. CIGS technology has been successfully used to produce high efficiency flexible and lightweight cells and modules, which address markets where heavy and rigid panels cannot be used. Perovskite solar cells, promise low cost solar technology based on abundant materials. Combining both technologies in a flexible and lightweight package expands the horizon of high performance, flexible, and customizable solar technology.

Korver Corp., an emerging solar and renewable energy company, has provided an update regarding the Company's new strategic direction in the solar energy sector. Korver has now decided to focus on its mission to develop high-efficiency commercially-manufactured Perovskite Silicon Tandem (PST) solar cells.

Mark Brown, President and CEO of Korver Corp., stated, "Our prior research has resulted in the development of highly efficient Perovskite Silicon Tandem solar cells. We plan to reach an efficiency mark of over 30% on a commercial scale by combining perovskite solar with the best silicon technologies on the market today and our own proprietary innovations. Currently, we are working towards scalability and commercial manufacturing of our PST solar cells that could change the way the world produces and consumes energy on a grand scale. We are excited to take the first mover advantage with the next big thing in solar energy."

The recent Silicon PV/nPV conference in Lausanne, Switzerland, saw Solliance's announcement on the achievement of a major milestone in perovskite technology for application in future industrial high efficiency tandem photovoltaic cells and modules. Solliance announced realizing a perovskite cell that combines good cell efficiency with a very high near infrared transparency of 93%.

Also at the conference, ECN shows that when this perovskite cell is mechanically stacked on a 6 inch² silicon bottom cell with its proprietary MWT-SHJ (metal-wrap-through silicon heterojunction) design, 26.3% efficiency is achieved, an increase of 3.6% points over the efficiency of the directly illuminated silicon cell laminate.

Researchers from the University of California, Berkeley, and Lawrence Berkeley National Laboratory have developed a flexible perovskite solar cell that reaches an efficiency of 21.7%, a peak conversion efficiency of 26% and could be manufactured using a low cost roll-to-roll process.

Many previous attempts to merge two perovskite materials have failed because the materials degrade one another's electronic performance. This design was achieved using a new way of combining two perovskite solar cell materials ' each tuned to absorb a different wavelength or color of sunlight ' into one 'graded bandgap' solar cell that absorbs nearly the entire spectrum of visible light.

Researchers at the Hong Kong Polytechnic University (PolyU) have reported reaching 25.5% efficiency with a perovskite-silicon tandem solar cell. In the tandem cell, a perovskite solar cell is placed on top so that it can harvest the short wavelength photons, while the bottom layer coated with silicon absorbs the long wavelength photons. To further increase the conversion efficiency, the research team has applied three innovative approaches, involving the use of low-temperature annealing, a tri-layer of molybdenum trioxide/gold/molybdenum trioxide, and a haze film.

The PolyU team believes that the cost of solar energy can drop significantly thanks to that concept, as compared to silicon cells available in the market. The PolyU research team will continue to work on further increasing the efficiency as well as the performance of large-scale fabrication of perovskite-silicon solar cells.

Researchers at the Helmholtz-Zentrum Berlin (HZB) developed a process for coating perovskite layers with graphene for the first time, so that the graphene acts as a front contact.

A traditional silicon absorber converts the red portion of the solar spectrum very effectively into electrical energy, whereas the blue portions are partially lost as heat. To reduce this loss, the silicon cell can be combined with an additional solar cell that primarily converts the blue portions and a particularly effective complement to conventional silicon is perovskite. However, it is normally very difficult to provide the perovskite layer with a transparent front contact. While sputter deposition of indium tin oxide (ITO) is common practice for inorganic silicon solar cells, this technique destroys the organic components of a perovskite cell.