Stability - Page 4

Researchers from CHOSE (Centre for Hybrid and Organic Solar Energy) at Tor Vergata University of Rome, CNR-ISM and Saule Technologies have introduced an optimized blade coating process for the scalable fabrication of large-area (15 cm × 15 cm) perovskite solar modules with a nickel oxide hole transport layer, performed in ambient air and utilizing a non-toxic solvent system. 

The research group fabricated a 110 cm² perovskite solar module with an inverted configuration and a hole transport layer that uses nickel oxide instead of commonly utilized poly(triarylamine) (PTAA). The proposed architecture aims to achieve high efficiency that is competitive with PTAA-based panels while improving stability.

Researchers from China's Northwestern Polytechnical University, The Hong Kong University of Science and Technology, and Spain's Technical University of Madrid have developed a new lithium-free doping strategy to fabricate spiro-OMeTAD-based hole transport layers (HTLs) for applications in perovskite solar cell. A PV device built with a lithium salt-doped HTL achieved an efficiency of 25.45%.

Schematic illustration of a n-i-p PSC with spiro-OMeTAD HTLs doped by LiTFSI or Eu(TFSI)₂. Image from Nature Communications

The team's lithium-free doping strategy to fabricate a perovskite solar cell is based on a metal-free hole transport layer (HTL) made of spiro-OMeTAd that reportedly offers remarkable efficiency and stability levels. The research team explained that spiro-OMeTAD for perovskite cell applications is usually doped with a compound known as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to enhance hole extraction and conductivity. This kind of doping, however, requires time-intensive air-oxidization for 24 hours, which reportedly represents an obstacle to the commercial production of perovskite PV devices.

Researchers at the Nova University of Lisbon, University of Aveiro and University of York have created an ultra-thin perovskite solar cell with a checkerboard tile pattern that shields the perovskite layer from UV degradation. The design includes a luminescent down-shifting encapsulant, which enhances UV photon conversion and boosts overall efficiency.

The team provided background for this work, stating that advanced light management techniques can enhance the sunlight absorption of perovskite solar cells (PSCs). When located at the front, they may act as a UV barrier, which is paramount for protecting the perovskite layer against UV-enabled degradation. Although it was recently shown that photonic structures such as Escher-like patterns could approach the theoretical Lambertian-limit of light trapping, it remains challenging to also implement UV protection properties for these diffractive structures while maintaining broadband absorption gains. 

Researchers from the Chinese Academy of Sciences, Beijing Institute of Technology and Shanghai Lettee Perovskite Optoelectronic Technology have addressed the issue of residual tensile strain - which impedes the improvement of efficiency and intrinsic stability of perovskite solar cells (PSCs) (resulting from the perovskite lattice distortion and different thermal expansion coefficients). To this end, they proposed a molecule-triggered strain regulation and interfacial passivation strategy to enhance the efficiency and stability (especially photostability) of PSCs.

Their strategy utilizes the [2 + 2] cycloaddition reaction of 6-bromocoumarin-3-carboxylic acid ethyl ester (BAEE), consuming the incident UV light to suppress the tensile strain evolution. 

An international team of researchers, including ones from the University of Sydney, IEK-5 Photovoltaics at Forschungszentrum Jülich, Southern University of Science and Technology, UNSW and the University of Ljubljana, recently reported the use of a piperidinium bromide (PpBr) as an interlayer between C60 and perovskite. The interlayer was further optimized by introducing an additional oxygen atom on the opposite side of the NH²⁺. 

The tandem structure that the team used for demonstrations. Image credit: Advanced Energy Materials

This reportedly resulted in morpholinium bromide (MLBr) with increased dipole moment. Because of this, MLBr was highly effective in minimizing the energy band mismatch between perovskite and C60 layer for electron extraction while at the same time passivating defects. 

Researchers from Shenzhen University recently addressed the stability issue of organic–inorganic hybrid perovskites, which the team says is currently a barrier to their widespread commercial application in optoelectronic devices. In addition to enhancing perovskite stability, the real-time detection of aging status, aimed at monitoring the aging progression, holds paramount importance for both fundamental research and the commercialization of organic–inorganic hybrid perovskites.

Schematic diagram of the THz-TDS system. Image from:  Frontiers of Optoelectronics 

In their recent work, the team examined the aging status of perovskite in real-time by using terahertz time-domain spectroscopy. This technique is based on the resonant absorption of terahertz waves by phonons in the perovskite. As perovskites age, the intensity of phonon vibration modes associated with the Pb-I bonds decreases, leading to changes in the absorption peaks of terahertz waves at specific frequencies. Based on this, they proposed using the intensity of these terahertz absorption peaks as an indicator to measure the ageing degree of perovskites in real-time.

Sekisui Chemical and TERRA recently announced that they have commenced the first joint demonstration test in Japan to install film-type perovskite solar cells for agrivoltaics (solar sharing) at Sosa City, Chiba Prefecture on August 2, 2024.

Sekisui Chemical has created a 30 cm-wide roll-to-roll manufacturing process utilizing its original “sealing, film formation, materials and process technology,” and has reportedly confirmed 10 years equivalent of outdoor durability, which is critical to the development of film-type perovskite solar cells. Furthermore, this manufacturing process has been successfully used to produce film-type perovskite solar cells with a power generation efficiency of 15.0%. Development is being accelerated to further improve durability and power generation efficiency, as well as to establish manufacturing technology for 1 m-wide rolls.

BusinessKorea reports that researchers at the Ulsan National Institute of Science and Technology (UNIST) have significantly improved the efficiency and stability of perovskite solar cells by addressing defect issues.

Schematic of perovskite crystallinity changes and thickness-based photoluminescence analysis through the introduction of bidirectional tuning molecules. Source: BusinessKorea, UNIST

The UNIST team announced that a joint research team, led by Professors Kim Jin-young and Kim Dong-seok from the Department of Energy and Chemical Engineering, and Professor Lee Geun-sik from the Department of Chemistry, successfully introduced bidirectional tuning molecules between the perovskite photoactive layer and the electron transport layer.

An international team of researchers, including ones from the University of Toronto, University of Toledo, Northwestern University, Lawrence Berkeley National Laboratory, KAUST and more, recently developed an all-perovskite tandem device that is said to show reduced recombination losses in the cell’s bottom device and excellent stability.

Image credit: Northwestern University
 

To improve the perovskite solar cell’s surface, the scientists created partially non-conductive and non-functional areas that protect the perovskite area underneath from becoming defective. The team examined the addition of diamine to improve the perovskite solar cell’s surface. The scientists found that the process made the surface more stable and improved the overall performance, resulting in a power conversion efficiency of 27.4% with better stability.

Researchers from NREL, Yale University, Hong Kong Baptist University and The Hong Kong University of Science and Technology (HKUST) have designed a chiral-structured interface in perovskite solar cells, which reportedly enhances their reliability and power conversion efficiency.

Using the PSC developed by the team to power a mobile phone as a demo. Image from Techxplore, credit HKUST

The performance of PSCs still faces significant barriers to commercialization, particularly due to various stability issues under real-world conditions. A major challenge is, according to the team, the insufficient adhesion between the different layers of the cells, resulting in limited interfacial reliability. To address this issue, the team was inspired by the mechanical strength of natural chiral materials and constructed an unprecedented chiral-structured interface in PSCs, unlocking very high reliability.