Lead Halide Perovskite Quantum Dots To Enhance the Power Conversion Efficiency of Organic Solar Cells

Au nano-flower/organic polymer heterojunction-based cathode photochemical biosensor with reduction-accelerated quenching effect of porphyrin manganese

In this work, a novel reduction-accelerated quenching of manganese porphyrin (MnPP) based signal-off cathode photochemical (PEC) biosensor by using Au nano-flower/organic polymer (PTB7-Th) heterojunction as platform was proposed for ultrasensitive detection of Hg²⁺. Firstly, the photoactive PTB7-Th with Au nano-flower on electrode could form a typical Mott-Schottky heterojunction for acquiring an extremely high cathode signal. Meanwhile, the presence of target Hg²⁺ could bring in the formation of T-Hg²⁺-T based scissor-like DNA walker, which thus activated efficient Mg²⁺-specific DNAzyme based cleavage recycling to shear hairpin H2 on electrode to exposure abundant trigger sites of hybridization chain reaction (HCR) for in-situ decoration of quencher MnPP. Here, besides the steric hinderance and light competition effect of MnPP decorated DNA nanowires attributing to signal decrease, we for the first time testified the MnPP reduction-accelerated quenching that constantly consumed the photo-generated electron by using cyclic voltammetry (CV). As a result, the proposed biosensor had excellent sensitivity and selectivity to Hg²⁺ in the range of 1 fM-10 nM with a detection limit of 0.48 fM. The actual sample analysis showed that the biosensor could reliably and quantitatively identify Hg²⁺, indicating an excellent application prospect in routine detection.

Self-Supplied Electron Photoelectrochemical Biosensor with PTB7-Th as a Photoelectric Material and Biotin as an Efficient Quencher

In this work, a self-supplied electron photoelectrochemical (PEC) biosensor for sensitive determination of Pb²⁺ was established by utilizing donor-acceptor (D-A)-type PTB7-Th (poly{4,8-bis[5-(2-ethylhexyl) thiophen-2-yl]benzo[1,2-b,4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]-thiophene-4,6-diyl}) as a photoelectric material coupled with biotin as an efficient signal quencher. Impressively, compared with the traditional PEC signal quenchers, biotin was first applied as a PEC signal quencher in this work and it effectively avoided a cumbersome preparation process, complex DNA sequence design, and extra reagent assistance and greatly simplified experimental steps, which could achieve an efficient PEC signal quenching toward PTB7-Th. In addition, the execution of a DNAzyme-assisted Pb²⁺ recycling amplification reaction could release the quencher biotin, leading to the recovery of the PEC signal, thereby realizing the quantitative detection of Pb²⁺. Resultantly, the submitted self-supplied electron PEC biosensor presented an extensive coverage of assay Pb²⁺ (50 fM to 500 nM) along with a low determination limit (16.7 fM), which exhibited the advantages of high selectivity and excellent stability. Importantly, this work provided a powerful alternative to traditional heavy metal-ion assessment methods and possessed the potential for application in environment, biomedicine, and food-safety fields.

Recent progress and future prospects on halide perovskite nanocrystals for optoelectronics and beyond

As an emerging new class of semiconductor nanomaterials, halide perovskite (ABX3, X = Cl, Br, or I) nanocrystals (NCs) are attracting increasing attention owing to their great potential in optoelectronics and beyond. This field has experienced rapid breakthroughs over the past few years. In this comprehensive review, halide perovskite NCs that are either freestanding or embedded in a matrix (e.g., perovskites, metal-organic frameworks, glass) will be discussed. We will summarize recent progress on the synthesis and post-synthesis methods of halide perovskite NCs. Characterizations of halide perovskite NCs by using a variety of techniques will be present. Tremendous efforts to tailor the optical and electronic properties of halide perovskite NCs in terms of manipulating their size, surface, and component will be highlighted. Physical insights gained on the unique optical and charge-carrier transport properties will be provided. Importantly, the growing potential of halide perovskite NCs for advancing optoelectronic applications and beyond including light-emitting devices (LEDs), solar cells, scintillators and X-ray imaging, lasers, thin-film transistors (TFTs), artificial synapses, and light communication will be extensively discussed, along with prospecting their development in the future.

Colloidal Quantum Dot Solar Cells: Progressive Deposition Techniques and Future Prospects on Large-Area Fabrication

Colloidally grown nanosized semiconductors yield extremely high-quality optoelectronic materials. Many examples have pointed to near perfect photoluminescence quantum yields, allowing for technology-leading materials such as high purity color centers in display technology. Furthermore, because of high chemical yield, and improved understanding of the surfaces, these materials, particularly colloidal quantum dots (QDs) can also be ideal candidates for other optoelectronic applications. Given the urgent necessity toward carbon neutrality, electricity from solar photovoltaics will play a large role in the power generation sector. QDs are developed and shown dramatic improvements over the past 15 years as photoactive materials in photovoltaics with various innovative deposition properties which can lead to exceptionally low-cost and high-performance devices. Once the key issues related to charge transport in optically thick arrays are addressed, QD-based photovoltaic technology can become a better candidate for practical application. In this article, the authors show how the possibilities of different deposition techniques can bring QD-based solar cells to the industrial level and discuss the challenges for perovskite QD solar cells in particular, to achieve large-area fabrication for further advancing technology to solve pivotal energy and environmental issues.

Perovskite Quantum Dots in Solar Cells

Perovskite quantum dots (PQDs) have captured a host of researchers' attention due to their unique properties, which have been introduced to lots of optoelectronics areas, such as light-emitting diodes, lasers, photodetectors, and solar cells. Herein, the authors aim at reviewing the achievements of PQDs applied to solar cells in recent years. The engineering concerning surface ligands, additives, and hybrid composition for PQDSCs is outlined first, followed by analyzing the reasons of undesired performance of PQDSCs. Subsequently, a novel overview that PQDs are utilized to improve the photovoltaic performance of various kinds of solar cells, is provided. Finally, this review is summarized and some challenges and perspectives concerning PQDs are also discussed.

Application of Perovskite Quantum Dots as Absorber for Perovskite Solar Cell

Perovskite quantum dots (QDs) preserve the attractive properties of perovskite bulk materials and present additional advantages, owing to their quantum confinement effect, leading to their applicability as an absorber in perovskite solar cells. In this article, the issues and advantages of perovskite QDs are analyzed in terms of purification, device fabrication with perovskite QDs, light absorption, charge transport and stability. In addition, promising strategies to enhance perovskite QDs and QD-based solar cells are elucidated based on exchange chemistry (ion and ligand exchange), passivation engineering (ion and ligand passivation) and structure engineering (conventional/inverted, planar/mesoscopic and dimensionally graded structures). All these discussions will give a clue to the further development of perovskite QDs and thus the advancement of QD-based solar cells.

Excited-State Properties of Defected Halide Perovskite Quantum Dots: Insights from Computation

CsPbBr₃ quantum dots (QDs) have been recently suggested for their application as bright green light-emitting diodes (LEDs); however, their optical properties are yet to be fully understood and characterized. In this work, we utilize time-dependent density functional theory to analyze the ground and excited states of the CsPbBr₃ clusters in the presence of various low formation energy vacancy defects. Our study finds that the QD perovskites retain their defect tolerance with limited perturbance to the simulated UV-vis spectra. The exception to this general trend is that Br vacancies must be avoided, as they cause molecular orbital localization, resulting in trap states and lower LED performance. Blinking will likely still plague CsPbBr₃ QDs, given that the charged defects critically perturb the spectra via red-shifting and lower absorbance. Our study provides insight into the tunability of CsPbBr₃ QDs optical properties by understanding the nature of the electronic excitations and guiding improved development for high-performance LEDs.

Lead-free bright blue light-emitting cesium halide nanocrystals by zinc doping

Cesium lead halide perovskite nanocrystals (NCs) have attracted extensive attention for photoelectric device application due to their excellent optoelectronic properties. However, the toxicity of lead has hindered their commercialization. Consequently, lead free cesium metal halide NCs have been developed, but these materials suffer from low photoluminescence quantum yield (PLQY) and poor stability. Here, a new class of lead-free non-perovskite blue-emitting cesium bromine (CsBr) and cesium iodine (CsI) halide NCs are realized by zinc doping. High PLQYs of 79.05% and 78.95% are achieved by CsBr:Zn and CsI:Zn NCs, respectively, attributed to the improved local structural order and reduced strain between the lattices of the NCs after storing under ambient conditions for 20 to 30 days. Moreover, zinc doped cesium halide NCs show excellent air stability for at least 50 days. Our results for zinc doped cesium halide NCs have shown a new avenue to fabricate lead-free halide NCs for blue lighting and display applications.

High-Efficiency Perovskite Quantum Dot Hybrid Nonfullerene Organic Solar Cells with Near-Zero Driving Force

To take advantages of the intense absorption and fluorescence, high charge mobility, and high dielectric constant of CsPbI₃ perovskite quantum dots (PQDs), PQD hybrid nonfullerene organic solar cells (OSCs) are fabricated. Addition of PQDs leads to simultaneous enhancement of open-circuit voltage (V_OC ), short-circuit current density (J_SC ), and fill factor (FF); power conversion efficiencies are boosted from 11.6% to 13.2% for PTB7-Th:FOIC blend and from 15.4% to 16.6% for PM6:Y6 blend. Incorporation of PQDs dramatically increases the energy of the charge transfer state, resulting in near-zero driving force and improved V_OC . Interestingly, at near-zero driving force, the PQD hybrid OSCs show more efficient charge generation than the control device without PQDs, contributing to enhanced J_SC , due to the formation of cascade band structure and increased molecular ordering. The strong fluorescence of the PQDs enhances the external quantum efficiency of the electroluminescence of the active layer, which can reduce nonradiative recombination voltage loss. The high dielectric constant of the PQDs screens the Coulombic interactions and reduces charge recombination, which is beneficial for increased FF. This work may open up wide applicability of perovskite quantum dots and an avenue toward high-performance nonfullerene solar cells.

Photophysical properties of some novel tetraphenylimidazole derived BODIPY based fluorescent molecular rotors

In this work, we present tetraphenylimidazole-based BODIPYs (HPIB1–HPIB4) as fluorescent molecular rotors exhibiting aggregation induced emission, solid state fluorescence and appreciable sensitivity towards viscosity.