Giant Molecule Research Articles

Strength in Numbers: A Giant NIR‐II AIEgen with One‐for‐All Phototheranostic Features for Exceptional Orthotopic Bladder Cancer Treatment

AbstractOne‐for‐all phototheranostics that allows the simultaneous implementations of multiple optical imaging and therapeutic modalities by utilizing a single component, is growing into a sparkling frontier in cancer treatment. Of particular interest is phototheranostic agent with emission in the second near‐infrared (NIR‐II) window. Nevertheless, the practical uses of those conventional NIR‐II agents are severely impeded by their unsatisfactory features including insufficient stability, low synthetic yield, to be extended absorption/ emission wavelengths, and inefficient phototheranostic outcomes. Developing exceptional phototheranostic agents is thus highly desirable yet remains formidably challenging. Herein, we synthesized two novel N‐heteroacenes‐based NIR‐II luminogens, namely 2TT‐PPT and 4TT‐PBPT, by respectively employing pyrene‐fused phenaziothiadiazoles and pyrene‐fused bisphenaziothiadiazoles as acceptor skeletons. There is strength in numbers by increasing the fusing rings in N‐heteroacenes moieties and numbers of appended donors. Compared to less ring‐fused 2TT‐PPT, the giant molecule 4TT‐PBPT shows improved photophysical characteristics, such as enhanced light absorbance, red‐shifted wavelengths, higher brightness, favorable reactive oxygen species (ROS) generation, and elevated photothermal conversion efficiency, which render 4TT‐PBPT nanoparticles excellent fluorescence‐photoacoustic‐photothermal trimodal imaging guided photodynamic‐photothermal synergistic therapy for orthotopic bladder cancer.

Strength in Numbers: A Giant NIR-II AIEgen with One-for-All Phototheranostic Features for Exceptional Orthotopic Bladder Cancer Treatment.

One-for-all phototheranostics that allows the simultaneous implementations of multiple optical imaging and therapeutic modalities by utilizing a single component, is growing into a sparkling frontier in cancer treatment. Of particular interest is phototheranostic agent with emission in the second near-infrared (NIR-II) window. Nevertheless, the practical uses of those conventional NIR-II agents are severely impeded by their unsatisfactory features including insufficient stability, low synthetic yield, to be extended absorption/ emission wavelengths, and inefficient phototheranostic outcomes. Developing exceptional phototheranostic agents is thus highly desirable yet remains formidably challenging. Herein, we synthesized two novel N-heteroacenes-based NIR-II luminogens, namely 2TT-PPT and 4TT-PBPT, by respectively employing pyrene-fused phenaziothiadiazoles and pyrene-fused bisphenaziothiadiazoles as acceptor skeletons. There is strength in numbers by increasing the fusing rings in N-heteroacenes moieties and numbers of appended donors. Compared to less ring-fused 2TT-PPT, the giant molecule 4TT-PBPT shows improved photophysical characteristics, such as enhanced light absorbance, red-shifted wavelengths, higher brightness, favorable reactive oxygen species (ROS) generation, and elevated photothermal conversion efficiency, which render 4TT-PBPT nanoparticles excellent fluorescence-photoacoustic-photothermal trimodal imaging guided photodynamic-photothermal synergistic therapy for orthotopic bladder cancer.

Jamming Giant Molecules at Interface in Organic Photovoltaics to Improve Performance and Stability.

A novel approach for depositing the giant molecule acceptor (GMA) at the donor-acceptor interface to enhance the efficiency and stability of organic photovoltaic (OPV) devices through a designed interface-enhanced layer-by-layer device fabrication protocol is proposed. The giant molecule acceptor DQx-Ph is mixed with the polymer donor in the bottom layer to form a polymer donor fibril phase and a mixed phase, followed by subsequent deposition of the main acceptor L8-BO. The L8-BO solution swells the bottom layer and alters the localized morphology of the mixing phase, introducing L8-BO fibrillar crystallization and pushing DQx-Ph giant molecules outwards to the fibril interfaces. Through this approach, the localized morphology and optoelectronic property of the bulk heterojunction are optimized. This configuration maintains the superior transport properties of L8-BO while integrating the high open-circuit voltage characteristics of DQx-Ph. Additionally, exciton dissociation and charge generation are simultaneously enhanced, with suppressed energy losses. A power conversion efficiency of 19.9% with improved operational stability is achieved, underscoring the importance of GMA interface jamming in advancing OPV technology. This study provides new insights into the development of ancillary OPV materials to overcome the critical limitations in OPV, revealing innovative approaches for photovoltaic technologies.

Effect of Molecular Conformation on Intermolecular Interactions and Photovoltaic Performances of Giant Molecule Acceptors

AbstractThe molecular conformation of giant molecule acceptors (GMAs) plays a significant role in regulating the intermolecular interactions and their photovoltaic performances in organic solar cells (OSCs). For the linear GMA GT‐l, the stronger homo‐molecular interaction causes its aggregation being weakly affected by the donor, thus forming an ordered molecular stacking and proper phase separation in its blend film. The star‐shaped GMA GT‐s‐based blend film shows a dominant hetero‐molecular interaction that suppresses the aggregation of the donor and acceptor, resulting in smaller phase separation and more uniform vertical phase distribution. While for another star‐shaped GMA GTs, the weakest hetero‐molecular interaction causes its blend film to form larger phase separation. Therefore, the GT‐l based OSC with PM6 as donor shows the highest charge mobilities, the fastest charge transfer (CT) process, reduced energy loss and less charge recombination, contributing to a higher power conversion efficiency (PCE) of 19.03%. Comparatively, the PCEs of the OSCs based on GTs and GT‐s are 18.05% and 17.58% respectively. Notably, all the three GMAs based OSCs show excellent thermal stability and long‐term storage stability. This study provides a facile strategy by tuning the linking unit and its connecting mode for designing highly efficient and stable organic photovoltaic materials.

Progress in Non-Fullerene Acceptors: Evolution from Small to Giant Molecules.

With the rapid development of non-fullerene acceptors (NFAs), the power conversion efficiency (PCE) of organic solar cells (OSCs) is increasing. According to their different chemical structures, NFAs can initially be divided into two categories: small molecule acceptors (SMAs) and polymerized small molecule acceptors (PSMAs). Due to the strong absorption capacity and controllable energy levels, the PCE of devices based on SMAs has approached 20%. Compared with SMAs, PSMAs have advantages in stability and flexibility, and the PCE of PSMA-based devices has exceeded 18%. However, the higher synthesis cost and lower batch repeatability hinder its further development. Recently, the concept of giant molecule acceptors (GMAs) has been proposed. These materials have a clear molecular structure and are considered novel acceptor materials that combine the advantages of SMAs and PSMAs. Currently, the PCE of devices based on GMAs has exceeded 19%. In this review, we will introduce the latest developments in SMAs, PSMAs, and GMAs. Then, the advantages of GMAs and the relationship between their structure and performance will be analyzed. In the end, perspectives on the opportunities and challenges of these materials are provided, which could inspire further development of NFAs for advanced OSCs.

π-Extended giant dimeric acceptor as a third component enables highly efficient ternary organic solar cells with efficiency over 19.2%

Ternary strategy with a suitable third component is a successful strategy to improve the photovoltaic performance of organic solar cells (OSCs). Very recently, Y-series based giant molecule acceptors or oligomerized acceptors have emerged as promising materials for achieving highly efficient and stable binary OSCs, while application as third component for ternary OSCs is limited. Here a novel π-extended giant dimeric acceptor, GDF, is developed based on central Y series core fusion and rigid BDT as linker, and then incorporated into the state-of-the-art PM1:PC6 system to construct ternary OSCs. The GDF has a near planar backbone, resulting in increased π-conjugation, excellent crystallinity, and good electron transport capacity. When GDF is introduced into the PM1:PC6 system, it ensues in a cascade like the lowest unoccupied molecular orbitals (LUMO) energy level alignment, a complementary absorption band with PM1 and PC6, higher and balanced hole and electron mobility, slightly smaller domain size, and a higher exciton dissociation probability for PM1:PC6:GDF (1:1.1:0.1) blend film. As a consequence, the PM1:PC6:GDF (1:1.1:0.1) ternary OSC achieves a champion PCE of 19.22%, with a significantly higher open-circuit voltage and short-circuit current density, compared to 18.45% for the PM1:PC6 (1:1.2) binary OSC. Our findings show that employing a π-extended giant dimeric acceptor as a third component significantly improves the photovoltaic performance of ternary OSCs.

Efficient and Stable All-Small-Molecule Solar Cells Enabled by Incorporating a Designed Giant Molecule Acceptor

Efficient and Stable All-Small-Molecule Solar Cells Enabled by Incorporating a Designed Giant Molecule Acceptor

Giant molecule acceptors prepared by metal-free catalyzed reactions towards efficient organic solar cells.

Due to their defined structure and large molecular size, giant molecular acceptors (GMAs) have achieved significant progress in device efficiency and stability for organic solar cells. Unlike the classical synthesis of GMAs by Stille coupling, which still suffers from high cost and lack of environmental sustainability, this work develops three GMAs via metal-free catalyzed reactions. By introducing varying quantities of malononitrile groups into the linker, the optoelectric properties of GMAs can be significantly regulated. A GMA containing only one malononitrile in the central linker unit exhibits a favorable absorption range, energy levels, and molecular packing, consequently achieving high efficiency and stability. Therefore this work provides a feasible approach to developing low-cost and scalable GMAs.

Precise synthesis and photovoltaic properties of giant molecule acceptors

Series of giant molecule acceptors DY, TY and QY with two, three and four small molecule acceptor subunits are synthesized by a stepwise synthetic method and used for systematically investigating the influence of subunit numbers on the structure-property relationship from small molecule acceptor YDT to giant molecule acceptors and to polymerized small molecule acceptor PY-IT. Among these acceptors-based devices, the TY-based film shows proper donor/acceptor phase separation, higher charge transfer state yield and longer charge transfer state lifetime. Combining with the highest electron mobility, more efficient exciton dissociation and lower charge carrier recombination properties, the TY-based device exhibits the highest power conversion efficiency of 16.32%. These results indicate that the subunit number in these acceptors has significant influence on their photovoltaic properties. This stepwise synthetic method of giant molecule acceptors will be beneficial to diversify their structures and promote their applications in high-efficiency and stable organic solar cells.

Cost-effective synthesis of giant molecule acceptors (GMAs) for stable polymer solar cells

Cost-effective synthesis of giant molecule acceptors (GMAs) for stable polymer solar cells

Exploring fullerene-based superlattices self-assembled via giant molecules

Fullerene, as a novel building block of functional materials, possesses a wide range of intriguing properties, some of which are closely related to hierarchical structures. Advancing the methodology for manipulating fullerene hierarchical structures could facilitate developments of novel fullerene-based materials with desired properties. In the present work, we report our exploration of a series of fullerene-based unconventional spherical packing nanostructures, including Frank-Kasper (FK) A15 and σ phases as well as dodecagonal quasicrystalline (DDQC) phase in unary self-assembly systems of fullerene-based giant molecules. Also, in giant molecule binary blends, alloy-type spherical phases with high volume asymmetries such as FK Laves C14 (MgZn2) and C15 (MgCu2) phases and quasi-FK AlB2 phase can also be found. These observations showcase the feasibility of fabricating a wide range of fullerene-based superlattices through self-assembly of specifically designed giant molecules. Superlattice engineering offers a promising avenue for constructing specific structures and functions in order to achieve desired properties, in particular, for developing innovative fullerene-based materials.

Solution Self-Assembly of Amphiphilic Tadpole-like Giant Molecules Constructed by Monotethering Diblock Copolymer Chain onto a Nanoparticle.

The self-assembly behavior of a tadpole-like giant molecule (TGM) constructed from a hydrophobic nanoparticle (NP) monotethered by a single amphiphilic AB diblock copolymer chain was investigated by combining self-consistent field theory and density functional theory in solution. The effects of the hydrophobicities of the B blocks and NPs (i.e., solvent properties) on the self-assembly behavior of the TGMs were investigated in the cases of weak and strong intramolecular interactions (i.e., incompatibilities) between the components of giant molecules, respectively. Besides conventional ordered aggregates (such as spheres, rings, and vesicles) with hydrophobic B-cores covered by NP shells, several aggregates with novel hierarchical structures, including vesicles with NP-inserted hydrophobic walls, bead-string-like micelles, and long cylindrical micelles with NP bumps, were obtained by tuning the solvent properties under different intramolecular interactions. Noteworthy that the simulation results show that the arrangement of the NP bumps on the long cylindrical micelles may have a certain degree of helicity, which means that these micelles may have some unique electromagnetic features such as circular dichroism. Phase diagrams as a function of the hydrophobicities of the B blocks and NPs were constructed to show the formation conditions of these novel structures. These findings can not only offer new insights into understanding of the self-assembly behavior of the TGM in solution but also provide useful guidance for simple and efficient regulation of the morphology, as well as the NP distribution and arrangement of the ordered aggregates in experiments.

Modular-Approach Synthesis of Giant Molecule Acceptors via Lewis-Acid-Catalyzed Knoevenagel Condensation for Stable Polymer Solar Cells.

The operational stability of polymer solar cells is a critical concern with respect to the thermodynamic relaxation of acceptor-donor-acceptor (A-D-A) or A-DA'D-A structured small molecule acceptors (SMAs) within their blends with polymer donors. Giant molecule acceptors (GMAs) bearing SMAs as subunits offer a solution to this issue, while their classical synthesis via the Stille coupling suffers from low reaction efficiency and difficulty in obtaining mono-brominated SMA, rendering the approach impractical for their large-scale and low-cost preparation. In this study, we present a simple and cost-effective solution to this challenge through Lewis acid-catalyzed Knoevenagel condensation with boron trifluoride etherate (BF3∙OEt2) as catalyst. We demonstrated that the coupling of the monoaldehyde-terminated A-D-CHO unit and the methylene-based A-link-A (or its silyl enol ether counterpart) substrates can be quantitatively achieved within 30 minutes in the presence of acetic anhydride, affording a variety of GMAs connected via the flexible and conjugated linkers. The photophysical properties was fully studied, yielding a high device efficiency of over 18%. Our findings offer a promising alternative for the modular synthesis of GMAs with high yields, easier work up, and the widespread application of such methodology will undoubtedly accelerate the progress of stable polymer solar cells.

Modular‐Approach Synthesis of Giant Molecule Acceptors via Lewis‐Acid‐Catalyzed Knoevenagel Condensation for Stable Polymer Solar Cells

AbstractThe operational stability of polymer solar cells is a critical concern with respect to the thermodynamic relaxation of acceptor‐donor‐acceptor (A‐D‐A) or A‐DA'D‐A structured small‐molecule acceptors (SMAs) within their blends with polymer donors. Giant molecule acceptors (GMAs) bearing SMAs as subunits offer a solution to this issue, while their classical synthesis via the Stille coupling suffers from low reaction efficiency and difficulty in obtaining mono‐brominated SMA, rendering the approach impractical for their large‐scale and low‐cost preparation. In this study, we present a simple and cost‐effective solution to this challenge through Lewis acid‐catalyzed Knoevenagel condensation with boron trifluoride etherate (BF3 ⋅ OEt2) as catalyst. We demonstrated that the coupling of the monoaldehyde‐terminated A‐D‐CHO unit and the methylene‐based A‐link‐A (or its silyl enol ether counterpart) substrates can be quantitatively achieved within 30 minutes in the presence of acetic anhydride, affording a variety of GMAs connected via the flexible and conjugated linkers. The photophysical properties was fully studied, yielding a high device efficiency of over 18 %. Our findings offer a promising alternative for the modular synthesis of GMAs with high yields, easier work up, and the widespread application of such methodology will undoubtedly accelerate the progress of stable polymer solar cells.

Chiral and nonreciprocal single-photon scattering in a chiral-giant-molecule waveguide-QED system

We study chiral and nonreciprocal single-photon scattering in a chiral-giant-molecule waveguide-QED system. Here, the giant molecule consists of two coupled giant atoms, which interact with two linear waveguides, forming a four-port quantum device. We obtain the exact analytical expressions of the four scattering amplitudes using a real-space method. Under the Markovian limit, we find that the single-photon scattering behavior is determined by the coupling strength between the giant atoms and the waveguides, the coupling strength between the two giant atoms, and the nondipole effect caused by the phase accumulation of photons traveling between the coupling points. It is also found that chiral and nonreciprocal single-photon scattering can be realized by introducing the chiral coupling to break the symmetry in the coupling configuration between the giant molecule and the waveguides. In addition, an ideal chiral emitter-waveguide coupling enables a directional single-photon routing. In the non-Markovian regime, the scattering spectra are characterized by more abundant structures with multiple peaks and dips. In particular, we demonstrate that the non-Markovian retarded effect can induce the nonreciprocal single-photon scattering. Our results have potential applications in the design of optical quantum devices involving giant atoms, which can provide an efficient platform for studying chiral quantum optics.

Giant Molecule Acceptor Enables Highly Efficient Organic Solar Cells Processed Using Non‐halogenated Solvent

AbstractHigh efficiency organic solar cells (OSCs) based on A‐DA′D‐A type small molecule acceptors (SMAs) were mostly fabricated by toxic halogenated solvent processing, and power conversion efficiency (PCE) of the non‐halogenated solvent processed OSCs is mainly restricted by the excessive aggregation of the SMAs. To address this issue, we developed two vinyl π‐spacer linking‐site isomerized giant molecule acceptors (GMAs) with the π‐spacer linking on the inner carbon (EV‐i) or out carbon (EV‐o) of benzene end group of the SMA with longer alkyl side chains (ECOD) for the capability of non‐halogenated solvent‐processing. Interestingly, EV‐i possesses a twisted molecular structure but enhanced conjugation, while EV‐o shows a better planar molecular structure but weakened conjugation. The OSC with EV‐i as acceptor processed by the non‐halogenated solvent o‐xylene (o‐XY) demonstrated a higher PCE of 18.27 % than that of the devices based on the acceptor of ECOD (16.40 %) or EV‐o (2.50 %). 18.27 % is one of the highest PCEs among the OSCs fabricated from non‐halogenated solvents so far, benefitted from the suitable twisted structure, stronger absorbance and high charge carrier mobility of EV‐i. The results indicate that the GMAs with suitable linking site would be the excellent candidates for fabricating high performance OSCs processed by non‐halogenated solvents.

Giant Molecule Acceptor Enables Highly Efficient Organic Solar Cells Processed Using Non-halogenated Solvent.

High efficiency organic solar cells (OSCs) based on A-DA'D-A type small molecule acceptors (SMAs) were mostly fabricated by toxic halogenated solvent processing, and power conversion efficiency (PCE) of the non-halogenated solvent processed OSCs is mainly restricted by the excessive aggregation of the SMAs. To address this issue, we developed two vinyl π-spacer linking-site isomerized giant molecule acceptors (GMAs) with the π-spacer linking on the inner carbon (EV-i) or out carbon (EV-o) of benzene end group of the SMA with longer alkyl side chains (ECOD) for the capability of non-halogenated solvent-processing. Interestingly, EV-i possesses a twisted molecular structure but enhanced conjugation, while EV-o shows a better planar molecular structure but weakened conjugation. The OSC with EV-i as acceptor processed by the non-halogenated solvent o-xylene (o-XY) demonstrated a higher PCE of 18.27% than that of the devices based on the acceptor of ECOD (16.40%) or EV-o (2.50%). 18.27% is one of the highest PCEs among the OSCs fabricated from non-halogenated solvents so far, benefitted from the suitable twisted structure, stronger absorbance and high charge carrier mobility of EV-i. The results indicate that the GMAs with suitable linking site would be the excellent candidates for fabricating high performance OSCs processed by non-halogenated solvent.

Single-photon scattering in a giant-molecule waveguide-QED system

We study the coherent single-photon scattering in a one-dimensional waveguide coupled to a giant artificial molecule consisting of two coupled giant atoms. Since each giant atom couples to the waveguide via two coupling points, the couplings of the molecule with the waveguide have three different coupling configurations: the separated-, braided-, and nested-coupling cases. We obtain the exact expressions of the single-photon transmission and reflection amplitudes with the real-space approach. It is found that the behavior of the scattering spectra depends on the phase shift between two neighboring coupling points, the coupling configuration, and the coupling between the two giant atoms. Concretely, we study the photon scattering in both the Markovian and non-Markovian regimes, in which the photon propagating time between two neighboring coupling points is neglected and considered, respectively. Under the Markovian limit, the asymmetric Fano line shapes in different coupling configurations of the giant-molecule waveguide-QED system can be obtained by choosing proper phase shift, and the transmission window can be adjusted by the coupling strength between the two giant atoms in these three coupling configurations. In particular, multiple reflection peaks and dips in these configurations are revived in the non-Markovian regime. This paper will pave the way for the study of controllable single-photon devices based on the giant-molecule waveguide-QED systems.

Unimolecular Nanoparticles toward More Precise Regulations of Self‐Assembled Superlattices in Soft Matter

AbstractThe hierarchical self‐assembly process opens up great potential for the construction of nanostructural superlattices. Precise regulation of self‐assembled superlattices, however, remains a challenge. Even when the primary molecules are precise, the supramolecular motifs (or secondary building blocks) can vary dramatically. In the present work, we propose the concept of unimolecular nanoparticles (UMNPs). The UMNPs act as the supramolecular motif and directly pack into the superlattices. A highly branched giant molecule is presented. We systematically explore its conformations and the superlattice of this giant molecule. Moreover, intriguing complex phases are discovered when blending this UMNP with other conventional giant molecules. These binary mixtures provide direct evidence to support our previously proposed self‐sorting process in the self‐assembly of “soft alloys”. The concept of UMNPs offers a unique approach toward more precise regulation of self‐assembled superlattices in soft matter.

Unimolecular Nanoparticles toward More Precise Regulations of Self-Assembled Superlattices in Soft Matter.

The hierarchical self-assembly process opens up great potential for the construction of nanostructural superlattices. Precise regulation of self-assembled superlattices, however, remains a challenge. Even when the primary molecules are precise, the supramolecular motifs (or secondary building blocks) can vary dramatically. In the present work, we propose the concept of unimolecular nanoparticles (UMNPs). The UMNPs act as the supramolecular motif and directly pack into the superlattices. A highly branched giant molecule is presented. We systematically explore its conformations and the superlattice of this giant molecule. Moreover, intriguing complex phases are discovered when blending this UMNP with other conventional giant molecules. These binary mixtures provide direct evidence to support our previously proposed self-sorting process in the self-assembly of "soft alloys". The concept of UMNPs offers a unique approach toward more precise regulation of self-assembled superlattices in soft matter.