King Abdullah University of Science and Technology (KAUST) scientists, along with collaborators from Ulsan National Institute of Science and Technology (UNIST) and Chinese Academy of Sciences (CAS), have reported a new strategy to design perovskite solar cells (PSCs) that improves their stability and raises their efficiency.

Image credit: KAUST

Defects at the top and bottom interfaces of three-dimensional (3D) perovskite photo-absorbers diminish the performance and operational stability of PSCs due to charge recombination, ion migration, and electric-field inhomogeneities. In this recent work, the team demonstrated that long alkyl-amine ligands can generate near-phase pure two-dimensional (2D) perovskites at the top and bottom 3D perovskite interfaces and effectively resolves these issues.

Researchers at HZB's HySPRINT Innovation Lab, China's Tianjin University of Technology and Tianjin Institute of Power Sources have developed a non-laser additive method for manufacturing perovskite solar modules, in which an adjustable wire mask (AWM) was used to form the channels that were traditionally scribed by lasers. 

When module channels are made by conventional laser scribing, the heat-sensitive perovskite materials decompose, and the decomposition of perovskites in the open channel leads to reduced module stability. The electrode corrosion caused by the direct contact between the exposed perovskites and the metal electrode significantly increases the series resistance of the module. In this recent work, the team developed a non-laser additive method for manufacturing perovskite solar modules, in which an adjustable wire mask (AWM) was used to form the channels that were traditionally scribed by lasers. This method for making modules prevents contact between perovskites and electrodes. All layers, including perovskites, hole/electron transporting, and passivating and electrode layers, were fabricated via vapor-phase deposition, and by tuning the precursor composition, a power conversion efficiency (PCE) of 21.7% was obtained (0.1 cm²). 

Chinese perovskite PV manufacturer Wuxi UtmoLight has announced ‘a new world record’ for steady-state efficiency on large-size perovskite solar modules. It has achieved 20.7% efficiency on an 810 cm² module. The Company claims to have attained a certification to this efficiency level by China’s National Photovoltaic Industry Measurement and Testing Center. 

UtmoLight says it significantly improved the crystallization of perovskite films by regulating the stress of the perovskite bulk phase and interface during the process of film formation, without sharing other details. The Chinese company has been making efforts to establish industrial production of perovskite modules. Currently operating a 150 MW line in China, it aims to expand to a GW-scale perovskite PV production line.

Researchers at Korea's Pusan National University, Kyungpook National University, Switzerland's École Polytechnique Fédérale de Lausanne (EPFL) and University of Fribourg have pioneered an approach that not only rectifies lead leakage but also focuses on interfacial passivation. The team used the method to achieve perovskite solar cells with 21.7% power conversion energy.

The presence of lead ions in perovskite solar cells not only causes lead leakage, which is hazardous to the environment, but in the presence of moisture, the perovskite tends to degrade. Multiple approaches have been suggested to resolve this issue, including encapsulating the device and compositional engineering of the perovskite light absorbers. The crown ether was found to assist in resisting degradation due to moisture for 300 hours at room temperature and 85 percent humidity. In the study, the researchers tested many crown ethers, but found that B18C6 was the best for interfacial passivation.

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.