Porphyrin-incorporated 2D D-A polymers with over 8.5% polymer solar cell efficiency

β-meso-Fused pyrene-porphyrin scaffolds with panchromatic absorption features

The π-extension of porphyrins with pyrenes through the β-meso-fusion of five-membered rings is demonstrated. Three architectures resulting from combining up to two porphyrins and pyrenes were obtained straightforwardly in good overall yields. Although significantly planarized, the molecules retain excellent solubility and processability. Spectroscopic characterization and density-functional theory calculations reveal intriguing absorption features.

Biaxially Conjugated Materials for Organic Solar Cells

Organic solar cells (OSCs) represent one of the most important emerging photovoltaic technologies that can implement solar energy conversion efficiently. The chemical structure of organic semiconductors deployed in the active layer of OSCs plays a critical role in the photovoltaic performance and chemical/physical stability of relevant devices. With the structure innovation of organic semiconductors, especially nonfullerene acceptors (NFAs), the performance of OSCs have been promoted rapidly in recent years, with state-of-the-art power conversion efficiencies (PCEs) exceeding 19.5%. Compared with other photovoltaics like perovskite, the shortcoming of OSCs mainly lies in the high nonradiative recombination loss. However, the photocurrent density is superior in OSCs owing to the easy modulation of the NFA band gap toward the near-infrared region. In these regards, the effort to further boost the PCE of OSCs to achieve a milestone >21% should be devoted to reducing the nonradiative loss while further broadening the absorption band. Developing organic semiconductors with biaxially extended conjugated structures has provided a potential solution to achieve these goals. Herein, we summarize the design rules and performance progress of biaxially extended conjugated materials for OSCs. The descriptions are divided into two major categories, i.e., polymers and NFAs. For p-type polymers, we focus on the biaxial conjugation on some representative building blocks, e.g., polythiophene, triphenylamine, and quinoxaline. Whereas for n-type polymers, some structures with large conjugated planes in the normal direction are presented. We also elaborate on the biaxial conjugation strategies in NFAs with modification site at either the π-core or side-group. The general structure-property relationships are further retrieved within these materials, with focus on the short-wavelength absorption and nonradiative energy loss. Finally, we provide an outlook for the further structure modification strategies of biaxially conjugated materials toward highly efficient, stable, and industry-compatible OSCs.

M, Rehman MFU, Assiri MA, Mashhadi SMA, Akram MS, Lu C. Evaluating Zn-Porphyrin-Based Near-IR-Sensitive Non-Fullerene Acceptors for Efficient Panchromatic Organic Solar Cells

Porphyrin-based non-fullerene acceptors (NFAs) have shown pronounced potential for assembling low-bandgap materials with near-infrared (NIR) characteristics. Herein, panchromatic-type porphyrin-based molecules (POR1-POR5) are proposed by modulating end-capped acceptors of a highly efficient porphyrin-based NFA PORTFIC(POR) for organic solar cells (OSCs). Quantum chemical structure-property relationship has been studied to discover photovoltaic and optoelectronic characteristics of POR1-POR5. Results show that optoelectronic properties of the POR1-POR5 are better in all aspects when compared with the reference POR. All proposed NFAs particularly POR5 proved to be the preferable porphyrin-based NIR sensitive NFA for OSCs applications owing to lower energy gap (1.56 eV), transition energy (1.11 eV), binding energy (Eb =0.986 eV), electron mobility (λe =0.007013Eh ), hole mobility (λh =0.004686 Eh ), high λmax =1116.27 nm and open-circuit voltage (Voc =1.96 V) values in contrast to the reference POR and other proposed NFAs. This quantum chemical insight provides sufficient evidence about excellent potential of the proposed porphyrin-based NIR sensitive NFA derivatives for their use in OSCs.

Electron Donor-Acceptor Interface of TPPS/PDI Boosting Charge Transfer for Efficient Photocatalytic Hydrogen Evolution

Charge separation efficiency of photocatalysts is still the key scientific issue for solar-to-chemical energy conversion. In this work, an electron donor-acceptor (D-A) interface with high charge separation between TPPS (tetra(4-sulfonatophenyl)porphyrin) and PDI (perylene diimide) is successfully constructed for boosting photocatalytic H2 evolution. The TPPS/PDI with D-A interface shows excellent photocatalytic H2 evolution rate of 546.54 µmol h-1 (30.36 mmol h-1 g-1 ), which is 9.95 and 9.41 times higher than that of pure TPPS and PDI, respectively. The TPPS/PDI has a markedly stronger internal electric field, which is respectively 3.76 and 3.01 times higher than that of pure PDI and TPPS. The D-A interface with giant internal electric field efficiently facilitates charge separation and urges TPPS/PDI to have a longer excited state lifetime than single component. The work provides entirely new ideas for designing materials with D-A interface to realize high photocatalytic activity.

Photoresponsive metallopolymer nanoparticles for cancer theranostics

Over the past decades, transition metal complexes have been successfully used in anticancer phototherapies. They have shown promising properties in many different areas including photo-induced ligand exchange or release, rich excited state behavior, and versatile biochemical properties. When encorporated into polymeric frameworks and become part of nanostructures, photoresponsive metallopolymer nanoparticles (MPNs) show enhanced water solubility, extended blood circulation and increased tumor-specific accumulation, which greatly improves the tumor therapeutic effects compared to low-molecule-weight metal complexes. In this review, we aim to present the recent development of photoresponsive MPNs as therapeutic nanomedicines. This review will summarize four major areas separately, namely platinum-containing polymers, zinc-containing polymers, iridium-containing polymers and ruthenium-containing polymers. Representative MPNs of each type are discussed in terms of their design strategies, fabrication methods, and working mechanisms. Current challenges and future perspectives in this field are also highlighted.

Isomeric Pyrene-Porphyrins for Efficient Dye-Sensitized Solar Cells: An Unexpected Enhancement of the Photovoltaic Performance upon Structural Modification

Four pyrene-porphyrins were synthesized to study the isomer effect on the photovoltaic performance of dye-sensitized solar cells. One of these porphyrins is conjugated with a terminal pyrene, whereas the other three are each attached with a pyrene bearing an extra donor group. According to the positions of the extra donor and porphyrin core on pyrene, the 1,6-, 1,8-, and 2,7-isomers were compared for their fundamental and photovoltaic properties. For fundamental properties, UV-visible absorption, fluorescence emission, electrochemistry, and DFT calculations were carried out. For photovoltaic measurements, the seemingly inferior 1,8-isomer outperforms others with an overall efficiency of 10.30% under one-sun irradiation. Superior photovoltaic performance of the 1,8-isomeric dye may be related to the so-called umbrella effect. The findings of this work may provide insight into isomeric dye design for future applications.

Selective Adsorption of C60 in the Supramolecular Nanopatterns of Donor-Acceptor Porphyrin Derivatives

The nanostructure of active layers consisting of donor and acceptor molecules is responsible for the separation and transfer processes of charge carriers, which may result in different photoelectric conversion efficiencies of organic photovoltaic cells (OPVCs). Therefore, intensive study on the relationships among nanostructures, intermolecular interactions, and molecular chemical skeletons is necessary for preparing controlled nanostructures of active layers by designing photovoltaic molecules. In this research, the self-assembled nanopatterns of three (DPP-ZnP-E)2-based molecules on highly oriented pyrolytic graphite surface were probed by scanning tunneling microscopy and analyzed by density functional theory calculations. The results indicated that different bridges, diethynylene, diethynylene-dithienyl, and diethynylene-phenylene, in (DPP-ZnP-E)2-based molecules not only made a difference to intermolecular interactions and cooperated with molecule-substrate interactions, consequently affecting the packed nanopattern, but also influenced the adsorption of fullerene acceptors in the nanopatterns of (DPP-ZnP-E)2-based molecules. C₆₀ molecules were found to be selectively adsorbed atop the dithienyl groups of (DPP-ZnP-E)2-2T donor molecules probably by S···π interactions compared with (DPP-ZnP-E)2 or (DPP-ZnP-E)2-Ph molecules. This study on the assembled nanopatterns of the three (DPP-ZnP-E)2-based molecules would be conductive to (DPP-ZnP-E)2-based optoelectronic materials design in OPVCs.

Conjugated Donor-Acceptor Terpolymers Toward High-Efficiency Polymer Solar Cells

The development of conjugated alternating donor-acceptor (D-A) copolymers with various electron-rich and electron-deficient units in polymer backbones has boosted the power conversion efficiency (PCE) over 17% for polymer solar cells (PSCs) over the past two decades. However, further enhancements in PCEs for PSCs are still imperative to compensate their imperfect stability for fulfilling practical applications. Meanwhile development of these alternating D-A copolymers is highly demanding in creative design and syntheses of novel D and/or A monomers. In this regard, when being possible to adopt an existing monomer unit as a third component from its libraries, either a D' unit or an A' moiety, to the parent D-A type polymer backbones to afford conjugated D-A terpolymers, it will give a facile and cost-effective method to improve their light absorption and tune energy levels and also interchain packing synergistically. Moreover, the rationally controlled stoichiometry for these components in such terpolymers also provides access for further fine-tuning these factors, thus resulting in high-performance PSCs. Herein, based on their unique features, the recent progress of conjugated D-A terpolymers for efficient PSCs is reviewed and it is discussed how these factors influence their photovoltaic performance, for providing useful guidelines to design new terpolymers toward high-efficiency PSCs.

Porphyrin-Containing Polymer as a Superior Blue Light-Absorbing Additive To Afford High- Jsc Ternary Solar Cells

Integrating an additional component featuring complementary light absorption into binary polymer solar cells is a superior tactic to ameliorate solar cell efficiency and stability. An appropriate additive not only extends the absorption range but may also facilitate charge separation and transport processes. In this work, we elucidate the effects of incorporating a porphyrin-containing conjugated polymer (PPor-1), which displays absorption in 350-500 nm, into binary PTB7-Th:4TIC and PTB7-Th:ITIC blends, affording devices with an average power conversion efficiency approaching 9%. We successfully demonstrate that PPor-1 can be incorporated as an additive to impart improved J_sc (up to 19.1 mA cm^-2).

Porphyrin Antenna-Enriched BODIPY-Thiophene Copolymer for Efficient Solar Cells

Low bandgap A-π-D copolymer, P(BdP-DEHT), consisting of alternating BOronDIPYrromethene (BODIPY) and thiophene units bridged by ethynyl linkers, and its porphyrin-enriched analogue, P(BdP/Por-DEHT), were prepared, and their optical and electrochemical properties were studied. P(BdP-DEHT) exhibits strong absorption in the 500-800 nm range with an optical bandgap of 1.74 eV. On the basis of cyclic voltammetry, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels are evaluated to be -5.40 and -3.66 eV, respectively. After the anchoring of zinc(II) porphyrin on the BODIPY unit, P(BdP/Por-DEHT) displays broadened absorption, thanks to porphyrins, and the optical bandgap decreases to 1.59 eV because of extension of BODIPY conjugation. The resulting estimated HOMO and LUMO energy levels, respectively, move to -5.32 and -3.73 eV. After optimization of the P(BdP-DEHT) or P(BdP/Por-DEHT) to PC₇₁BM weight ratio to 1:2 in dichlorobenzene solution, the bulk heterojunction polymer solar cells show overall power conversion efficiencies (PCEs) of 3.03 and 3.86%, respectively. After solvent vapor annealing (SVA) treatment in CH₂Cl₂ for 40 s, the PCEs increased to 7.40% [V_oc of 0.95 V, J_sc of 12.77 mA/cm², and fill factor (FF) of 0.61 with energy loss of 0.79 eV] and 8.79% (V_oc of 0.92 V, J_sc of 14.48 mA/cm², and FF of 0.66 with energy loss of 0.67 eV). The increase in the PCE for P(BdP/Por-DEHT)-based devices is mainly attributed to the enhancement in J_sc and FF, which may be related to the broader absorption spectra, lower band gap, and better charge transport of P(BdP/Por-DEHT) compared to P(BdP-DEHT). This could also be related to the optimized nanoscale morphology of the active layer for both efficient exciton dissociation and charge transport toward the electrodes and a balanced charge transport in the device, induced by the SVA treatment of the active layer.

Two-dimensional light-emitting materials: preparation, properties and applications

We review the recent development in two-dimensional (2D) light-emitting materials and describe their preparation methods, optical/optoelectronic properties and applications.

Functional Organometallic Poly(arylene ethynylene)s: From Synthesis to Applications

This review focuses on the recent development in the rigid-rod metallopolymers of late transition metals based on triple-bond building blocks. The synthesis, structure-property relationships and potential applications of organometallic poly(arylene ethynylene)s will be discussed in detail. These functional metal-based polymers can exhibit intriguing optical, electronic and magnetic properties. Considerable focus is placed on the design strategies towards tuning the optical bandgap and emission color (spanning almost the whole visible spectrum) of this class of metallopolymers, and the investigation of their use as active materials for light/electrical energy conversion and energy and information storage. The ongoing scientific challenges and future prospects of this research field are also highlighted.

Biocompatible D-A Semiconducting Polymer Nanoparticle with Light-Harvesting Unit for Highly Effective Photoacoustic Imaging Guided Photothermal Therapy

The development of nanotheranostic agents that integrate diagnosis and therapy for effective personalized precision medicine has obtained tremendous attention in the past few decades. In this report, biocompatible electron donor-acceptor conjugated semiconducting polymer nanoparticles (PPor-PEG NPs) with light-harvesting unit is prepared and developed for highly effective photoacoustic imaging guided photothermal therapy. To the best of our knowledge, it is the first time that the concept of light-harvesting unit is exploited for enhancing the photoacoustic signal and photothermal energy conversion in polymer-based theranostic agent. Combined with additional merits including donor-acceptor pair to favor electron transfer and fluorescence quenching effect after NP formation, the photothermal conversion efficiency of the PPor-PEG NPs is determined to be 62.3%, which is the highest value among reported polymer NPs. Moreover, the as-prepared PPor-PEG NP not only exhibits a remarkable cell-killing ability but also achieves 100% tumor elimination, demonstrating its excellent photothermal therapeutic efficacy. Finally, the as-prepared water-dispersible PPor-PEG NPs show good biocompatibility and biosafety, making them a promising candidate for future clinical applications in cancer theranostics.

Cyclometalated Pt complex-based random terpolymers for efficient polymer solar cells

A terpolymer approach was introduced to increase the power conversion efficiency of solar cells by embedding small amounts of Pt-complex into PTB7-Th.

Regular conjugated D–A copolymer containing two benzotriazole and benzothiadiazole acceptors and dithienosilole donor units for photovoltaic application

Synthesized a D–A copolymer with low bandgap of 1.53 eV, and used as donor for PSCs. The over PCE of the PSC is reached 8.91% with a low voltage loss of 0.59 eV.

Synthesis and side-chain isomeric effect of 4,9-/5,10-dialkylated-β-angular-shaped naphthodithiophenes-based donor–acceptor copolymers for polymer solar cells and field-effect transistors

P4,9-βNDTDTFBT:PC₇₁BM-based solar cell device achieves a high PCE of 7.23%.

A Porphyrin-Based Conjugated Polymer for Highly Efficient In Vitro and In Vivo Photothermal Therapy

Conjugated polymers have been increasingly studied for photothermal therapy (PTT) because of their merits including large absorption coefficient, facile tuning of exciton energy dissipation through nonradiative decay, and good therapeutic efficacy. The high photothermal conversion efficiency (PCE) is the key to realize efficient PTT. Herein, a donor-acceptor (D-A) structured porphyrin-containing conjugated polymer (PorCP) is reported for efficient PTT in vitro and in vivo. The D-A structure introduces intramolecular charge transfer along the backbone, resulting in redshifted Q band, broadened absorption, and increased extinction coefficient as compared to the state-of-art porphyrin-based photothermal reagent. Through nanoencapsulation, the dense packing of a large number of PorCP molecules in a single nanoparticle (NP) leads to favorable nonradiative decay, good photostability, and high extinction coefficient of 4.23 × 10⁴ m^-1 cm^-1 at 800 nm based on porphyrin molar concentration and the highest PCE of 63.8% among conjugated polymer NPs. With the aid of coloaded fluorescent conjugated polymer, the cellular uptake and distribution of the PorCP in vitro can be clearly visualized, which also shows effective photothermal tumor ablation in vitro and in vivo. This research indicates a new design route of conjugated polymer-based photothermal therapeutic materials for potential personalized theranostic nanomedicine.

Photovoltaic Small Molecules of TPA(FxBT-T-Cz)3: Tuning Open-Circuit Voltage over 1.0 V for Their Organic Solar Cells by Increasing Fluorine Substitution

To simultaneously improve both open-circuit voltage (V_oc) and short-circuit current density (J_sc) for organic solar cells, a novel D(A-π-Ar)₃ type of photovoltaic small molecules of TPA(F_xBT-T-3Cz)₃ was designed and synthesized, which contain central triphenylamine (TPA), terminal carbazole (Cz), armed fluorine-substituted benzothiadiazole (F_xBT, where x = 1 or 2), and bridged thiophene (T) units. A narrowed ultraviolet-visible absorption and a decreasing highest occupied molecular orbital energy level were observed from TPA(F₁BT-T-3Cz)₃ to TPA(F₂BT-T-3Cz)₃ with increasing fluorine substitution. However, the TPA(F₂BT-T-3Cz)₃/PC₇₁BM-based solar devices showed a rising V_oc of 1.01 V and an enhanced J_sc of 10.84 mA cm^-2 as well as a comparable power conversion efficiency of 4.81% in comparison to the TPA(F₁BT-T-3Cz)₃/PC₇₁BM-based devices. Furthermore, in comparison to the parent TPA(BT-T-3Cz)₃ molecule without fluorine substitution, the fluorine-substituted TPA(F_xBT-T-3Cz)₃ molecules exhibited significantly incremental V_oc and J_sc values in their bulk heterojunction organic solar cells, owing to fluorine incorporation in the electron-deficient benzothiadiazole unit.

High efficiency all-polymer tandem solar cells

In this work, we have reported for the first time an efficient all-polymer tandem cell using identical sub-cells based on P2F-DO:N2200. A high power conversion efficiency (PCE) of 6.70% was achieved, which is among the highest efficiencies for all polymer solar cells and 43% larger than the PCE of single junction cell. The largely improved device performance can be mainly attributed to the enhanced absorption of tandem cell. Meanwhile, the carrier collection in device remains efficient by optimizing the recombination layer and sub-cell film thickness. Thus tandem structure can become an easy approach to effectively boost the performance of current all polymer solar cells.

Photocurrent in Multilayered Assemblies of Porphyrin-Fullerene Covalent Dyads: Evidence for Channels for Charge Transport

Specially designed porphyrin-fullerene dyads have been synthesized to verify literature predictions based on quantum chemistry calculations that certain porphyrin-fullerene dyads are able to self-arrange into specific structures providing channels for charge transport in a bulk mass of organic compound. According to AFM and SEM data, the newly synthesized compounds were indeed prone to some kind of self-arrangement, although to a lesser degree than was expected. A dispersion corrected DFT study of the molecular non-covalent interactions performed at the DFT-D3 (B3LYP, 6-31G*) level of theory showed that the least energy corresponded to head-to-head dimers, with close contacts of porphyrin-porphyrin and fullerene-fullerene fragments, thus providing a unit building block of the channel for charge transport. Experimental proof for the existence of channels for charge transport was obtained by observing a photocurrent in a simple photovoltaic cell.

A Difluorobenzoxadiazole Building Block for Efficient Polymer Solar Cells

A difluorobenzoxadiazole building block is synthesized and utilized to construct a conjugated polymer leading to high-performance thick-film polymer solar cells with a V(OC) of 0.88 V and a power conversion efficiency of 9.4%. This new building block can be used in many possible polymer structures for various organic electro-nic applications.

Random terpolymer with a cost-effective monomer and comparable efficiency to PTB7-Th for bulk-heterojunction polymer solar cells

A new random terpolymer PTB7-Th-T2 was designed and synthesized for high performance PSCs by incorporating a significantly lower-cost 2,2′-bithiophene monomer to the famous PTB7-Th skeleton.

Enhancing the photovoltaic properties of low bandgap terpolymers based on benzodithiophene and phenanthrophenazine by introducing different second acceptor units

Two D–A type random terpolymers PBDTT-PPzIID and PBDTT-PPzDPP were synthesized by copolymerizing a donor and two acceptor units. The PBDTT-PPzDPP-based device shown a PCE of 5.91%.

Molecular-structure control of electron transfer dynamics of push–pull porphyrins as sensitizers for NiO based dye sensitized solar cells

Zn(ii)-porphyrin dyes for NiO dye-sensitized solar cells showed surprisingly rapid charge recombination, in spite of their push–pull character. Appending a secondary acceptor prolonged charge separation and led to improved photovoltaic performance.

A novel porphyrin-containing polyimide for memory devices

A novel porphyrin-based polyimide ZnPor-t-DSDA was synthesized for memory applications and exhibits symmetric biswitching characteristic with a short retention time due to the coplanar structure between donor and acceptor units.