Stability

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.

Researchers from the Chinese Academy of Sciences (CAS) posit that the efficiency and stability of perovskite modules are mainly limited by the quality of scalable perovskite films and sub-cells’ lateral contact. So, in their recent work, they addressed this by reporting constant low temperature substrates to regulate the growth of perovskite intermediate films to slow down the crystallization process. This is meant to assist in obtaining high-quality homogeneous perovskite films in large scale size, which avoid the effect of the ambient temperature on the film quality. 

Schematic diagram of the fabrication process of perovskite films using low-temperature substrate growth (LTSG). Image from Nature Communications

In addition, a scribing step named P1.5 was added before the top function layers deposition, so the diffusion barrier layer can be formed “naturally” at the interconnection interface without introducing any additional materials, which alleviates the diffusion degradation process. 

Rayleigh solar Tech has announced two significant lifetime stability results. First, a 15cm x 15cm glass solar module exhibited zero degradation after seven months of outdoor testing. Second, a 15cm x 15cm flexible solar module achieved T80 after 1200 hours of damp heat testing.

“Stability is the crux of any perovskite company’s business model” said Rayleigh CTO and Founder, Dr. Sam March. “This is a huge step towards the commercial viability of our perovskite PV. Rayleigh’s all-ambient slot-die coated carbon-based perovskite solar modules are efficient, low-cost, and are stable in the field”, he said.