Stability - Page 2

Researchers at the Hong Kong Polytechnic University (PolyU) and Hong Kong University of Science and Technology (HKUST) have developed an innovative laminated interface microstructure that enhances the stability and photoelectric conversion efficiency of inverted perovskite solar cells.

Prof. ZHOU Yuanyuan, Associate Professor in the Department of Chemical and Biological Engineering (CBE) and Associate Director of the Energy Institute at HKUST, leads a team focused on fundamental research into perovskite optoelectronic devices from a unique structural perspective. They collaborated closely with Prof. CAI Songhua’s team from the Department of Applied Physics at PolyU. Their research revealed that by uniformly creating a “molecular passivation layer-fullerene derivative layer-2D perovskite layer”—a “three-ply” laminated structure on the surface of the perovskite film—they could effectively reduce the density of interface defects and improve energy level alignment. This advancement substantially boosts the photoelectric conversion efficiency of the perovskite solar cell and enhances the durability of the interface under damp-heat and light soaking conditions.

Ultraviolet (UV)-induced damage and limited solar spectrum utilization can hinder the performance of perovskite solar cells (PSCs). In a recent study, researchers from Fuzhou University and Chinese Academy of Sciences developed a thermally activated delayed fluorescent (TADF) molecule, 4CzIPN, to address these challenges. 

Acting as a down-conversion agent, 4CzIPN can convert UV light to visible light via Förster energy transfer, enhancing light absorption and reducing photon loss. Additionally, it can bind Pb²⁺ defects and prevents organic cation degradation through cationic π-effects, stabilizing the perovskite structure. By serving as a crystal growth site, 4CzIPN can promote intermediate phase formation and delay the crystallization process, and improve film quality while mitigating residual stress due to its high thermal expansion coefficient. Furthermore, its UV filtration and hydrophobic properties would reduce perovskite decomposition and device degradation.

Researchers from Korea's Pusan National University, Gyeongsang National University, Ajou University and Switzerland's Zurich University of Applied Sciences have addressed the stability issue of perovskite solar cells (PSCs), namely the weak adhesion of C60 to perovskite layers, due to van der Waals interactions, that hinders long-term stability. 

The team developed electron-deficient intermolecular adhesives (EDIAs) as a novel interlayer material to enhance adhesion between perovskite and C60 layers. Comprehensive analyses, including density functional theory calculations, microscopy, and spectroscopy, demonstrated that EDIAs, particularly NDI-C9-Ace comprising of three key functionalities: a π-electron-deficient arene core, a hydrophobic passivation core, and a secondary-bond anchoring core, significantly improved bonding strength and recombination passivation.

Scientists at the Chinese Academy of Sciences (CAS), Xuancheng Kaisheng New Energy Technology Company and Tianjin Institute of Power Sources have found a way to make flexible tandem solar cells more efficient and durable by enhancing the adhesion of top layers to the bottom layers of the cell.

Copper indium gallium selenide (CIGS) is a commercial semiconductor known for its outstanding adjustable bandgap, strong light absorption, low-temperature sensitivity, and superior operational stability, making it a promising candidate for bottom-cell use in next-generation tandem solar cells. Flexible perovskite/CIGS tandem solar cells combine a top layer of perovskite with a bottom layer of CIGS. This tandem cell holds great potential for lightweight, high-efficiency applications in the photovoltaic field but the rough surface of CIGS makes it difficult to produce high-quality perovskite top cells on top, which limits the commercial prospects of these tandem cells.

Researchers from Ulsan National Institute of Science and Technology (UNIST), Gyeongsang National University (GNU) and University of Ulsan explain that in spiro-OMeTAD-based hole-transporting layer (HTL) protocols, 4-tert-butylpyridine (tBP) is an indispensable component; however, its inclusion leads to substantial detrimental effects, hindering thermal stability. 

Recently, the team developed a tBP-free spiro-OMeTAD approach by substituting ethylene carbonate (EC) electrolyte for tBP. The electronegative carbonyl functionality led to the formation of a solvation complex with Li⁺ ions, addressing the solubility concern of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in chlorobenzene even without tBP. 

Researchers from Daegu Gyeongbuk Institute of Science and Technology (DGIST), Lawrence Berkeley National Laboratory, University of California and Pohang University of Science and Technology (POSTECH) have observed and identified the water-induced degradation mechanism of perovskite in real time at the atomic scale. 

Image from: Matter

This recent study presents key strategies for enhancing the stability of perovskite materials and could accelerate their commercialization. 

NiOx shows promise for large-area perovskite technologies thanks to excellent semiconductor properties, ease of large-area deposition, and tunable optoelectronic characteristics. However, NiOx-based perovskite solar cells (PSCs) tend to be limited by interfacial photocatalytic chemical reactions and energy level mismatch. Thus, phosphate-based self-assembled monolayers (SAMs) have been developed for delicate interfacial modification but these suffer from severe issues such as self-aggregation and high cost.

Image from: Journal of Energy Chemistry

Researchers from China's Fudan University and Shanghai Geoharbour Construction Group have addressed this issue by developing a low-cost carboxylate-based SAM (pyrenebutyric acid, PyBA) to modify NiOx, achieving an improved surface chemical environment and interfacial properties, such as an increased Ni³⁺/Ni²⁺ ratio, a reduced proportion of high-valence Ni^≥3+, and better-aligned hole transport interface energy level. 

The inhomogeneity of hole-selective self-assembled molecular layers (SAMLs) often arises from the insufficient bonding between anchors and metal oxides, particularly on textured silicon surfaces when fabricating monolithic perovskite/silicon tandem solar cells (P/S-TSCs) and the hydrophobic carbazole complicates the fabrication of high-quality perovskite films. 

To address this, researchers from the Chinese Academy of Sciences (CAS), Advanced Solar Technology Institute of Xuancheng and North Minzu University have developed a bidentate-anchored superwetting aromatic SAM based on an upside-down carbazole core as a hole-selective layer (HSL), denoted as ((9H-carbazole-3,6-diyl)bis(4,1-phenylene))bis(phosphonic acid) (2PhPA-CzH). 

Researchers from EPFL, National University of Singapore and Nanjing University of Aeronautics and Astronautics have used lattice strain to lock in rubidium, which helped cut energy loss and push perovskite solar cells to 93.5% of their theoretical efficiency limit. By utilizing the controlled distortion in the atomic structure, this approach not only stabilized the wide-bandgap (WBG) perovskite but also improved efficiency by cutting non-radiative recombination, a major cause of energy loss.

Known for absorbing high-energy light while letting lower-energy light pass, wide-bandgap materials offer major gains in energy capture but are prone to phase segregation, a phenomenon that takes place when different components of the material separate over time, leading to a decline in performance. While adding rubidium to help stabilize the semiconductors has been proposed as a potential way to address the issue, the element often forms unwanted secondary phases, which limits its ability to strengthen the perovskite structure. However, the scientists fine-tuned the material’s composition in a process that involved rapid heating followed by controlled cooling. This created lattice strain, that prevented rubidium from forming unwanted secondary phases and kept it integrated within the crystal structure.

Researchers from the University of Potsdam, TU Berlin, HZB, BHT Berlin and Salerno University have reported halide perovskite photovoltaics (PV) fabricated on regolith-based moonglass that could be produced on the Moon, thereby saving 99% of material transport weight. Regolith is a silicate-rich material that covers the Moon’s surface. 

Image from: Device

This method reportedly enables effective specific power ratios, over 22–50 W/g, a factor of 20–100 higher compared to traditional space PV solutions, while not compromising radiation shielding, reliability, and mechanical stability as was the case until now.