Technical / research - Page 5

Researchers from Duke University, University of Colorado - Boulder, Israel's Weizmann Institute of Science, Polish Academy of Sciences and University of Lille CNRS have examined the local structure of halide perovskites in their molten and glassy states, revealing the critical connection between these structures and the contrasting properties observed in their crystalline vs glassy states. 

The findings of this work enhance scientists' understanding of the diverse structural motifs in perovskites and how structural changes in perovskite glass impact their properties, paving the way for advancements in next-generation phase change materials and devices.

A team of researchers, led by Professor David Di from the International College of Zhejiang University and the School of Optoelectronic Science and Engineering, recently achieved a continuous transition from n-type to p-type perovskite semiconductors through molecular doping, while maintaining extremely high luminescence performance. 

Image credit: Zhejiang University

Based on controllable doping, the team developed a perovskite LED with a simple structure and reported a record for the highest brightness of solution-based LEDs, reaching 1.16 million nits.

Researchers from Korea's Ulsan National Institute of Science and Technology (UNIST) have addressed critical challenges in perovskite solar cells (PSCs), significantly enhancing both their efficiency and stability. The team achieved precise control over ion arrangement and reduced structural irregularities by incorporating a bidirectional coordinator between the perovskite photoactive layer and the electron transport layer.

Image credit: UNIST

The research team introduced trifluoroacetate (TFA-) ions between the perovskite layer and the tin oxide substrate, which serves as the electron transport layer (ETL), to mitigate defects.

Researchers from Ming Chi University of Technology, National Taiwan University of Science and Technology and Chang Gung University have explored the effect of self-assembled monolayers (SAMs), readily deposited via spin-coating, on defect passivation in sol–gel NiOx for perovskite solar cells (PSCs).

The team explained that while mixed-halide PSCs are highly attractive for indoor light-harvesting applications (thanks to their tunable bandgap and low-cost fabrication), achieving efficient carrier transport and defect passivation at the critical nickel oxide (NiOx)/perovskite interface, particularly under low light conditions, remains a challenge. Self-assembled monolayers (SAMs) offer a promising solution by introducing a tailored interface that promotes perovskite growth, suppresses non-radiative recombination, and facilitates efficient carrier transport. 

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 China's Hebei University of Technology have developed a scalable method combining physical thermal field and chemical bonding to fabricate inch-sized FAPbI₃ wafers. By integrating 120 °C hot-pressing to stabilize the photoactive α phase and polyaniline polymer to conduct and passivate the grain boundaries, the team obtained quasi-single crystal FAPbI₃ wafers on a large scale. 

This approach reportedly overcomes the critical challenges of phase impurities and high-density defects, enhancing the phase stability of the FAPbI₃ wafers. 

Interface engineering is widely used to enhance the efficiency and stability of photodetectors (PDs). Researchers from China's Guangxi University have explained that although fluorine-containing materials are ideal for interface modification, they are seldom used at the NiOx/perovskite interface. Their recent paper reports on the use of Tris(pentafluorophenyl)borane (BCF) and 2,3,5,6-tetrafluoro-7,7,8,8- tetracyanoquinodimethane (F4-TCNQ)-modified NiOx HTL to achieve high-efficiency and high-stability PDs. 

This work shows that BCF and F4-TCNQ interact to provide better doping ability, form Lewis adducts with Pb²⁺, and enhance the crystallinity of their perovskites. Interaction with nickel oxide optimizes the Ni³⁺/Ni²⁺ ratio, thus improving conductivity and charge transport capability. The F4-TCNQ:BCF modification effectively reduces interface defects, improves carrier mobility, and enhances both the performance and stability of PDs in ambient air. 

Researchers from Seoul National University, University of Pennsylvania, Weizmann Institute of Science and Korea Basic Science Institute (KBSI) recently reported an advancement in the development of ultra-high efficiency perovskite nanocrystal light-emitting diodes (LEDs). Their work involved reinforcing the perovskite lattice and mitigating the material's natural low-frequency dynamics. 

The team identified a critical challenge in the reduction of luminescence efficiency due to the ionic nature of perovskite. The weak ionic bonds in perovskite materials can cause large-amplitude displacement of atoms within the crystal lattice, resulting in dynamic disorder that interferes with the radiative recombination process, leading to exciton dissociation and decreased luminescence efficiency. Addressing this issue, however, has been underexplored until now. The team proposed a novel mechanism to enhance the luminescence efficiency of perovskite emitters by incorporating conjugated molecular multipods (CMMs). These CMMs bind to the perovskite lattice, strengthening it and reducing dynamic disorder, which in turn improves the luminescence efficiency.

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. 

Researchers from China's Huazhong University of Science and Technology, Wuhan University of Technology and Huaneng Clean Energy Research Institute have reported a surface reconstruction strategy utilizing a surface polishing agent, 1,4-butanediamine, together with a surface passivator, ethylenediammonium diiodide, to eliminate Sn-related defects and passivate organic cation and halide vacancy defects on the surface of Sn–Pb mixed perovskite films. 

The team explained that while all-perovskite tandem solar cells have shown great promise in breaking the Shockley–Queisser limit of single-junction solar cell, their efficiency is often hindered by the surface defects induced non-radiative recombination loss in Sn–Pb mixed narrow bandgap perovskite films. The strategy detailed in their recent work not only delivers high-quality Sn–Pb mixed perovskite films with a close-to-ideal stoichiometric ratio surface, but also minimizes the non-radiative energy loss at the perovskite/electron transport layer interface.