Stability

Researchers at Hong Kong Baptist University, The Hong Kong University of Science and Technology (HKUST) and Yale University have revealed the existence of surface concavities on individual crystal grains that are the fundamental blocks of perovskite thin films, and examined their significant effects on the film properties and reliability. 

Based on this discovery, the team designed a new way of making perovskite solar cells (PSCs) more efficient and stable via a chemo-elimination of these grain surface concavities.

Researchers at the National Renewable Energy Laboratory (NREL) and University of North Carolina at Chapel Hill have reported a systematic study on the degradation mechanisms of p–i–n structure perovskite solar cells (PSCs) under reverse bias. Reverse bias is a phenomenon that can occur when, for example, an individual cell is shaded and other cells in the module try to push a higher current through it, increasing the temperature and potential damage to the cells. These conditions make solar cells unstable and deteriorate their performance over time.

The team's new strategy could improve the stability of PSCs under reverse bias conditions and facilitate the future deployment of perovskite-based photovoltaics (PVs) in real-world settings.

Researchers at The University of Toledo (UToledo), Northwestern University and University of Washington have focused on the stability of perovskite solar cells, and reported an adjustment to the chemical structure of a key component of a tandem cell that allows it to continuously generate electricity for more than 1,000 hours.

Image from Joule

“State-of-the-art all-perovskite tandem cells with a conventional hole-transfer layer can only continuously operate for hundreds of hours,” said Dr. Zhaoning Song, a co-author and assistant professor in the Department of Physics and Astronomy at UToledo. “Our innovation prolongs the stability of these devices, advancing all-perovskite tandem technology and bringing it closer to practical application.”

Researchers from Peking University, Tsinghua University, Beijing Institute of Technology and Ecole Polytechnique Fédérale de Lausanne (EPFL) have tackled a reproducibility challenge in black-phase formamidinium lead iodide (α-FAPbI₃) perovskites. They explained that while this is the desired phase for photovoltaic applications, water can trigger formation of photoinactive impurity phases such as δ-FAPbI₃. The team found that the classic solvent system for perovskite fabrication exacerbates this reproducibility issue. 

Growth of the photoactive black phase of formamidinium lead iodide (α-FAPbI₃) usually requires dimethyl sulfoxide solvent, but the hygroscopic nature of this chemical also promotes water-induced degradation to the photoinactive phase. the scientists showed that a larger chlorinated organic molecule can form a hydrophobic capping layer that enables perovskite crystallization under humid conditions by protecting growing crystallites from water. 

Researchers from Northwestern University, University of Toronto and KAUST have hypothesized that perovskitoids, with robust organic-inorganic networks enabled by edge- and face-sharing, could impede ion migration. This addresses the issue of the migration of cations between 2D and 3D layers which results in the disruption of octahedral networks that leads to degradation in performance over time

The scientists explored a set of perovskitoids of varying dimensionality, and found that cation migration within perovskitoid/perovskite heterostructures was suppressed compared to the 2D/3D perovskite case. Increasing the dimensionality of perovskitoids improves charge transport when they are interfaced with 3D perovskite surfaces – the result of enhanced octahedral connectivity and out-of-plane orientation. 

Researchers from China's Zhejiang University, Westlake University, Southern University of Science and Technology, Chinese Academy of Sciences (CAS) and University of California Los Angeles in the U.S have reported a family of high-entropy organic–inorganic hybrid perovskites for photovoltaic applications.  

The scientists built, for the first time, an inverted perovskite solar cell relying on a high-entropy hybrid perovskite material. The result is a device with an improved open-circuit voltage and fill factor, due to reduced non-radiative recombinations and optimized interface.

Researchers at CHOSE (Centre for Hybrid and Organic Solar Energy, University of Rome Tor Vergata), BeDimensional, Istituto Italiano di Tecnologia and GreatCell Solar Italia recently addressed the stability issues presented by perovskite solar cells, by developing an industrial encapsulation process based on the lamination of highly viscoelastic semi-solid/highly viscous liquid adhesive atop perovskite solar cells and modules. 

Sketch of the structure of the mesoscopic n-i-p PSCs. Image credit: Nature Communications 

The encapsulant reportedly reduces the thermomechanical stresses at the encapsulant/rear electrode interface. The addition of thermally conductive two-dimensional hexagonal boron nitride into the polymeric matrix improves the barrier and thermal management properties of the encapsulant. Without any edge sealant, encapsulated devices withstood multifaceted accelerated ageing tests, retaining >80% of their initial efficiency.

Researchers from Zhejiang University, LinkZill Technology, Jilin University, and Linköping University have found that the electroluminescence rise time of perovskite LEDs (PeLEDs) can be reduced to microseconds using an individual-particle passivation strategy. This addresses a known issue with PeLEDs, that tend to have electroluminescence rise times over milliseconds due to ion migration in crystal structure, which is problematic for the development of high-refresh-rate displays.

The team demonstrated a second-generation digital display screen that uses perovskite light-emitting diodes instead of standard LED technology. In their study, the group made improvements to the device and demonstrated its sensing capability.

Researchers from Colombia's Universidad de los Andes recently set out to develop inverted perovskite solar cells (IPSCs) with a hole transport layer based on indium-doped nickel oxide. The result is a champion device that achieved an efficiency of 20.06% with remarkable stability.

The team explained that NiOx has an energy gap of over 3.5 eV, exceptional chemical stability, durability, low toxicity, and cost-effective processing. The scientists said that in the case of NiOx-based inverted perovskite solar cells, the doping approach has indeed paved the way for HTL optimization, frequently through observable improvements also at the interface level and in the perovskite layer.

Researchers from Monash University, Xi’an Jiaotong University, Tunghai University, the University of Oxford, National Central University, and the City University of Hong Kong have developed a strategy to enhance the stability and performance of perovskite solar cells (PSCs) through a mechanism described as 'self-healing'.

The team reported a living passivation strategy using a hindered urea/thiocarbamate bond Lewis acid-base material (HUBLA), where dynamic covalent bonds with water and heat-activated characteristics can dynamically heal the perovskite to ensure device performance and stability.