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.

Scientists from Switzerland's EPFL and the Toyota Motor Corporation have prepared a detailed analysis of the projected costs of designing and operating a 100 MW perovskite solar cell production line in various locations, taking under consideration factors like labor and energy costs as well as all materials and processing. The team found that perovskite PV could be cost-competitive with other technologies even at much smaller scale, but noted that this still depends on the tech proving its long-term stability, and impressive achievements in research being successfully transferred to commercial production.

While perovskite materials have been repeatedly demonstrating their potential for low-cost, high-efficiency solar energy with lower energy fabrication compared to silicon PV technology, there are still many different possibilities regarding the form these commercial products could take, and the materials they could contain - with more than one option that could prove commercially viable.

Researchers from Switzerland's Federal Laboratories for Materials Science and Technology (EMPA) and École Polytechnique Fédérale de Lausanne (EPFL) have designed a four-terminal tandem mini-module based on perovskite and copper, indium, gallium and selenium (CIGS) with an aperture area of around 2 cm², and a geometric fill factor of over 93%.

Processing sequence of flexible NIR-transparent perovskite mini-module. Image from RRL Solar

The team reports that the key to efficient flexible perovskite-CIGS tandem modules is the development of near-infrared (NIR) transparent perovskite solar modules on a flexible polymer foil. To achieve these results, the researchers had to overcome the challenges of laser patterning on flexible substrates to realize the first all-laser scribed monolithically interconnected NIR-transparent perovskite mini-modules on polymer film. The perovskite mini-module used in the tandem panel was fabricated on a flexible polyethylene napthalathe (PEN) substrate mounted to a glass substrate in a p–i–n device architecture. This configuration, according to the research team, shows reduced absorption in the NIR region.

Researchers from the Swiss Center for Electronics and Microtechnology (CSEM) and the École polytechnique fédérale de Lausanne (EPFL) have reported a power conversion efficiency exceeding 30% for a 1 cm² tandem perovskite-silicon solar cell, which represents a world record for a PV device of this kind. The team achieved an efficiency of 30.93% for a 1 cm² solar cell based on high-quality perovskite layers from solution on a planarized silicon surface and an efficiency of 31.25% on a cell of the same size and fabricated with a hybrid vapor/solution processing technique compatible with a textured silicon surface.

“These results constitute two new world records: one for the planar and one for the textured device architecture,” the researchers explained, noting that both efficiencies were certified by the US Department of Energy's National Renewable Energy Laboratory (NREL). “The latter approach provides a higher current and is compatible with the structure of current industrial silicon solar cells”. Unfortunately, the researchers did not disclose technical details on how they improved the efficiency of both devices.

Researchers from Fraunhofer Institute for Solar Energy Systems ISE, EPFL, Korea Basic Science Institute (KBSI) and Morocco's Abdelmalek Essaadi University have developed a perovskite solar cell with a carbon electrode that achieved 18.5% efficiency.

Schematic diagram of the investigated low-temperature carbon electrode-based PSC with 3D/2D perovskite treated by OAI. Image from study

The solar cell also reportedly retained 82% of their efficiency after 500 hours of continuous illumination. The cell is produced via all low-temperature processes that could likely be scaled into low-cost, large-scale manufacturing ' making the approach attractive despite achieving lower efficiency than record-setting cells.

EPFL scientists in Neuchâtel have reported a tandem solar cell that can deliver a certified efficiency of 29.2%. This achievement was made possible by combining a perovskite solar cell with a textured silicon solar cell.

One obstacle the team encountered was finding a way to evenly coat the silicon surface'which is intentionally rough, or textured'with a thin film of halide perovskites. A textured surface is used in order to minimize light reflection. This kind of system can already be found in all commercially available crystalline silicon cells.

Researchers from EPFL, Tianjin University, Nanjing Tech University, The University of Tokyo, Shanghai University and Toyota Motor Corporation have used ionic liquids (ILs) with halide anions as additives to improve the performance and stability of a perovskite solar cell.

Image from study in Cell Reports Physical Science

Ionic liquids are viewed as a "greener" alternative to organic solvents due to their lower volatility and flammability, as well as to their wide liquid-state window.

A team of scientists, led by Mohammad Nazeeruddin at École polytechnique fédérale de Lausanne (EPFL), has found a way to address the scaling up challenges of perovskites. The scientists have developed an easy solvothermal method to produce single-crystalline titanium dioxide rhombohedral nanoparticles that can be used to build a perovskite film.

The new structure is said to feature a lower amount of lattice mismatches, referring to the "ladder-like" structure of the titanium dioxide nanoparticles. This translates into a lower number of defects, which ensures better electron flow throughout with lower power loss.

Researchers from the University of Rome Tor Vergata's Centre for Hybrid and Organic Solar Energy (CHOSE), IMEC and EPFL have reported on a solar module with an efficiency of 20.72%, based on tin oxide (SnO₂) as an electron transport layer, an organometal halide perovskite layer, organic halide salt phenethylammonium iodide (PEAI) as a passivation agent, and Spiro-OMeTAD as the hole transport layer (HTL).

The international research team presented its low-temperature planar perovskite module with an n'i'p architecture, an aperture area of 11'cm², and a geometrical fill factor of 91%.

An international team of researchers from EPFL, North Carolina State University, Centre for Hybrid and Organic Solar Energy (CHOSE) at the University of Rome Tor Vergata and Uppsala University has demonstrated a technique for producing perovskite photovoltaic materials on an industrial scale, which could reduce the cost and improve the performance of mass-produced perovskite solar cells. The technique is low-cost, simple and energy-efficient.

'In the lab, researchers produce perovskite photovoltaic materials using a technique called spin coating, which creates a thin film of perovskite on a substrate ' but only on a small scale,' says Aram Amassian, co-corresponding author of a paper on the work and a professor of materials science and engineering at North Carolina State University.