Researchers at the National Renewable Energy Laboratory (NREL) report the creation of an efficient tandem perovskite solar cell, using a new chemical formula which also improved the structural and optoelectronic properties of the solar cell.

Most of the research efforts in the field of PSCs have focused on lead-based perovskites, which have a wide bandgap. High efficiency, low bandgap perovskites would enable the fabrication of very high efficiency all-perovskite tandem solar cells where each layer absorbs only a part of the solar spectrum and is optimally configured to convert this light into electrical energy. However, low bandgap perovskites have long suffered from large energy losses and instability limiting their use in tandems.

Researchers at the Energy Research Center of the Netherlands (ECN) have developed a bifacial tandem solar cell with a conversion efficiency of 30.2%. The new cell device ' created with Dutch consortium Solliance ' was made by applying a newly developed perovskite cell on top of an industrial bifacial crystalline silicon version.

This approach, according to the scientists, enables a significantly higher power conversion efficiency as one cell is optimized for high energy photons, and the other low energy particles. 'The tandem device proposed here uses a four-terminal configuration, thus having separate circuits for the top and bottom cells that allow for dynamic fine tuning and optimization of the energy yield,' the creators of the cell wrote. The cell is also said to be better able to capture light on its front and rear sides by responding to the variability of incident light through its electronic design.

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 the Germany-based Helmholtz Center Berlin (HZB) have announced a thin-film solar cell made of perovskite and copper-indium-gallium-selenide (CIGS) with an efficiency of 21.6%.

The HZB researchers said they used a simple, robust production process suitable for scaling up. Rutger Schlatmann, director of the HZB's Institute PVcomB, spoke of an 'enormous step in the direction of commercial production'. The HZB team's tandem cell could theoretically reach an efficiency of more than 30%, according to the researchers.

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.

Oxford PV, a leading developer of perovskite solar cells, has announced a new, certified, 28% efficiency world record for its perovskite-based solar cell.

Oxford PV's 1 cm² perovskite-silicon tandem solar cell has achieved a 28% conversion efficiency, certified by the National Renewable Energy Laboratory. The achievement trumps Oxford PV's previous certified record of 27.3% efficiency for its perovskite-silicon solar cell, announced earlier this year.

Researchers from the Australian National University (ANU), in collaboration with researchers from and the California Institute of Technology, have developed a way to combine silicon with perovskites to achieve higher efficiencies and lower production costs. They believe that this could lead to cheaper and more efficient solar technology.

The new way to create crystalline silicon and perovskite tandem PV cells is claimed by the team to be the simplest method of doing so.

Researchers from Arizona State University have achieved 25.4% efficiency in their tandem solar cell stacked with perovskite and silicon. This follows, and surpasses, last year's achievement of 23.6% efficiency.

The team's improvement upon the record by nearly two percentage points was reached in a joint project with researchers at the University of Nebraska'Lincoln, predicting they'll be nearing 30% tandem efficiency within two years.

Researchers at Helmholtz-Zentrum Berlin (HZB) have demonstrated 25.5% efficiency for monolithic perovskite/silicon tandem solar cells using textured foil. In addition, the impact of texture position on performance and energy yield is simulated in their new work.

Tandem solar cell device schematics of the experimentally realized architecture and SEM cross section image of the top cell

The research team used a textured light management (LM) foil on the front-side of a tandem solar cell processed on a wafer with planar front-side and textured back-side. Consequently, the PCE of monolithic, 2-terminal perovskite/silicon-heterojunction tandem solar cells was improved from 23.4% to 25.5%. This approach replaced the use of textured silicon wafers, that can be utilized for light management but are typically not compatible with perovskite solution processing.

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."