Researchers from MIT, University of Cambridge, University of Washington and Korea Research Institute of Chemical Technology have reported a set of recommendations for how to tune surface properties of perovskites - ways to optimize efficiency and better control degradation, by engineering the nanoscale structure of perovskite devices - towards the commercialization of perovskite-based solar cells.

The recent work addresses the two main hurdles that have been plaguing perovskite solar cells: their longevity and the challenge of maintaining high efficiency across larger module areas.

Researchers from Nanjing University, University of Victoria and Australian National University have achieved a high conversion efficiency of 24.5% on large-size all-perovskite tandem solar cells. The result, which the team states is a new world record for the efficiency of all-perovskite tandem solar cells, has reporetdly been confirmed by an international third-party testing institute.

When a lead-tin perovskite is used instead of silicon as the narrow band gap cell in all-perovskite tandem solar cells, the result is often low film quality and device efficiency due to nonuniform nucleation and fast crystallization. In this recent work, the team shows that aminoacetamide hydrochloride can strongly coordinate the precursor components in solution, which homogenizes the crystallization process and also passivates the buried perovskite interface. The authors achieved a certified power conversion efficiency of 24.5% for a 20-square-centimeter module made by blade-coating the layers. 

Researchers at the University of Victoria in Canada and Solaires Enterprises have designed a flexible perovskite solar cell with an active area of 0.049 cm² based on a polyethylene terephthalate (PET) substrate and a reactant known as phenyltrimethylammonium chloride (PTACl) in ambient air fabrication.  Tested under standard illumination conditions, the flexible perovskite device achieved a power conversion efficiency of 17.6%, an open-circuit voltage of 0.95 V, a short-circuit current density of 23 mA cm⁻², and a fill factor of 80%.

The team explained that PET is cheaper than commonly utilized polyethylene naphthalate (PEN) in substrates for flexible solar cells, with the latter having however the advantage of being more thermally stable during the production process. PET, by contrast, has a maximum temperature tolerance of 100 C and can tolerate deposition procedures under this threshold. For this reason, the research group chose a cell architecture with a substrate made of PET and indium tin oxide (ITO), an electron transport layer (ETL) based on tin oxide (SnO₂), a methylammonium lead iodide (MAPbI₃) perovskite absorber, a Spiro-OMeTAD hole-transporting layer (HTL), and a gold (Au) metal contact.

An international team of researchers from King Abdullah University of Science and Technology (KAUST), Ulsan National Institute of Science and Technology (UNIST) and the Chinese Academy of Sciences have reportedly developed an inverted perovskite solar cell incorporating low-dimensional perovskite layers at the solar cell's top and bottom interfaces. 

The team achieved optimal passivation in inverted perovskite solar cells by applying thin layers of low-dimensional perovskite on top of a 3D perovskite film. The resulting cell achieved an open-circuit voltage of 1.19 V, a short-circuit current density of 24.94 mA cm², and a fill factor of 85.9%.

Researchers from the Korea Institute of Energy Research (KIER), Korea Research Institute of Standards and Science, Jusung Engineering and the Jülich Research Center have reported an advancement in the stability and efficiency of semi-transparent perovskite solar cells.

The semi-transparent solar cells achieved an impressive efficiency of 21.68%, which is said to be the highest efficiency to date among perovskite solar cells that use transparent electrodes. Additionally, they showed remarkable durability, with over 99% of their initial efficiency maintained after 240 hours of operation.

Researchers at the Karlsruhe Institute of Technology (KIT), Institute for Solar Energy Research Hamelin (ISFH) and Leibniz University Hannover have designed triple-junction perovskite–perovskite–silicon solar cells with a record power conversion efficiency of 24.4%. 

Schematic of the solar cell. Image from Energy & Environmental Science

Optimizing the light management of each perovskite sub-cell (∼1.84 and ∼1.52 eV for top and middle cells, respectively), the team maximized the current generation up to 11.6 mA cm⁻². Key to this achievement was the development of a high-performance middle perovskite sub-cell, employing a stable pure-α-phase high-quality formamidinium lead iodide perovskite thin film (free of wrinkles, cracks, and pinholes). This enabled a high open-circuit voltage of 2.84 V in a triple junction. Non-encapsulated triple-junction devices retain up to 96.6% of their initial efficiency if stored in the dark at 85 °C for 1081 h.

Lead-halide perovskites hold great promise as the next generation of PVs, but unstable lead exposure through gas, water, and soil accumulation could have detrimental consequences if not properly controlled and recycled as perovskite use expands globally. There are also stability issues limiting operational lifetime for lead-perovskite devices themselves. Researchers have attempted to replace lead with slightly less toxic tin, but thus far tin-based perovskites still suffer from air instability. Without breakthroughs in stability and environmental safety, scaling perovskite solar technology could flood our waste stream with hazardous materials. Now, researchers from CHOSE (Centre for Hybrid and Organic Solar Energy) at the University of Rome Tor Vergata have addressed the concerns regarding toxicity and recyclability associated with the lead contained in perovskite solar cells. 

Image credit: ACS Energy Letters 

The scientists may have found a solution in a new lead-free antimony-based perovskite solar cell design. Their recent research demonstrates a mixed-cation perovskite-inspired material (PIM) that boosted efficiency by 81% compared to conventional cesium-only antimony solar cells, while also exhibiting unmatched stability.

Researchers at the University of North Carolina at Chapel Hill and CubicPV have developed mini solar modules based on perovskite cells treated with zinc trifluoromethane sulfonate [Zn(OOSCF₃)₂]. The scientists found that using a small amount of this zinc salt in the perovskite solution can address the issue of interstitial iodides, which are the most critical type of defects in perovskite solar cells that limits efficiency and stability. The zinc salt helps control the iodide defects in resultant perovskites ink and films. 

The scientists explained that this is a low-cost material that is used as an additive at a very small percentage in perovskite inks and that its use makes perovskite module fabrication more reproducible, which helps to also make it cheaper.

Researchers at Ulsan National Institute of Science and Technology (UNIST) recently set out to develop a scalable photoelectrochemical (PEC) system to produce green hydrogen.

(a) Concept design of NiFeOOH/Ni/FAPbI3 photoanode-based water splitting cell. (b) All-PSK-based encapsulated PEC reactor made of repeated mini-modules. Credit: Nature Energy & Dr Dharmesh Hansora, UNIST

The team explained that for practical photoelectrochemical water splitting to become a reality, highly efficient, stable and scalable photoelectrodes are essential. However, meeting these requirements simultaneously is a difficult task, as improvements in one area can often lead to deterioration in others. To address this challenge, the team developed a formamidinium lead triiodide (FAPbI₃) perovskite-based photoanode that is encapsulated by an Ni foil/NiFeOOH electrocatalyst, which demonstrates promising efficiency, stability and scalability. 

Researchers from Japan's National Institute for Materials Science (NIMS) and Hokkaido University have designed an inverted “n-i-p” perovskite solar cell with a new bond/charge regulated defect passivation technique, enabled by introducing bifunctional molecules onto the perovskite absorber. The device exhibited a low open circuit voltage deficit and impressive stability.

The newly-fabricated solar cell with was based on a perovskite material that doesn't contain methylammonium (MA) molecules. These molecules have intrinsic thermal instability and contribute to increasing the typical thermal instability of perovskite PV devices.