Self-Assembled Interlayer Enables High-Performance Organic Photovoltaics with Power Conversion Efficiency Exceeding 20.

Interfacial layers (ILs) are prerequisites to form the selective charge transport for high-performance organic photovoltaics (OPVs) but mostly result in considerable parasitic absorption loss. Trimming the ILs down to a mono-molecular level via the self-assembled monolayer is an effective strategy to mitigate parasitic absorption loss. However, such a strategy suffers from inferior electrical contact with low surface coverage on rough surfaces and poor producibility. To address these issues, here, the self-assembled interlayer (SAI) strategy is developed, which involves a thin layer of 2-6 nm to form a full coverage on the substrate via both covalent and van der Waals bonds by using a self-assembled molecule of 2-(9H-carbazol-9-yl) (2PACz). Via the facile spin coating without further rinsing and annealing process, it not only optimizes the electrical and optical properties of OPVs, which enables a world-record efficiency of 20.17% (19.79% certified) but also simplifies the tedious processing procedure. Moreover, the SAI strategy is especially useful in improving the absorbing selectivity for semi-transparent OPVs, which enables a record light utilization efficiency of 5.34%. This work provides an effective strategy of SAI to optimize the optical and electrical properties of OPVs for high-performance and solar window applications.

Chlorella pyrenoidosa mitigated the negative effect of cylindrospermopsin-producing and non-cylindrospermopsin-producing Raphidiopsis raciborskii on Daphnia magna as a dietary supplement.

Feeding effects are crucial for evaluating the capacity of zooplankton to regulate phytoplankton populations within freshwater ecosystems. To examine the impact of the bloom-forming cyanobacteria Raphidiopsis raciborskii, which occurs in tropical and subtropical freshwaters, on the growth of zooplankton Daphnia in relation to toxins, filament length and fatty acid content, we fed D. magna with R. raciborskii only (cylindrospermopsin (CYN)-producing and non-CYN-producing, as the negative controls), Chlorella pyrenoidosa only (as the positive control) and a mixed diet containing R. raciborskii (CYN-producing and non-CYN-producing) and C. pyrenoidosa. Consequently, our findings revealed that the toxic effect of CYN-producing R. raciborskii strains on Daphnia was mitigated by the coexistence of C. pyrenoidosa containing stearidonic acid (SDA, C18:4 ω3) in mixed diets. This was evident in the elevated survival rate compared that from diets containing only R. raciborskii and a significantly higher reproduction and population intrinsic increase rate compared to diets consisting of only R. raciborskii or C. pyrenoidos. Additionally, a strong positive correlation was observed between arachidonic acid (ARA, 20:4ω6) and the population intrinsic increase rate of Daphnia; notably, R. raciborskii strains were found to be rich in the ω6 polyunsaturated fatty acid ARA. These outcomes reinforce the crucial role of polyunsaturated fatty acids in predicting the population increase of crustacean zooplankton, which has long been neglected. Furthermore, our results underscore the potential effectiveness of zooplankton, particularly in temperate lakes, in controlling CYN-producing R. raciborskii populations.

Solid Additive-Assisted Layer-by-Layer Processing for 19% Efficiency Binary Organic Solar Cells.

Morphology is of great significance to the performance of organic solar cells (OSCs), since appropriate morphology could not only promote the exciton dissociation, but also reduce the charge recombination. In this work, we have developed a solid additive-assisted layer-by-layer (SAA-LBL) processing to fabricate high-efficiency OSCs. By adding the solid additive of fatty acid (FA) into polymer donor PM6 solution, controllable pre-phase separation forms between PM6 and FA. This intermixed morphology facilitates the diffusion of acceptor Y6 into the donor PM6 during the LBL processing, due to the good miscibility and fast-solvation of the FA with chloroform solution dripping. Interestingly, this results in the desired morphology with refined phase-separated domain and vertical phase-separation structure to better balance the charge transport /collection and exciton dissociation. Consequently, the binary single junction OSCs based on PM6:Y6 blend reach champion power conversion efficiency (PCE) of 18.16% with SAA-LBL processing, which can be generally applicable to diverse systems, e.g., the PM6:L8-BO-based devices and thick-film devices. The efficacy of SAA-LBL is confirmed in binary OSCs based on PM6:L8-BO, where record PCEs of 19.02% and 16.44% are realized for devices with 100 and 250 nm active layers, respectively. The work provides a simple but effective way to control the morphology for high-efficiency OSCs and demonstrates the SAA-LBL processing a promising methodology for boosting the industrial manufacturing of OSCs.

Compromising Charge Generation and Recombination of Organic Photovoltaics with Mixed Diluent Strategy for Certified 19.4% Efficiency.

The ternary blend is demonstrated as an effective strategy to promote the device performance of organic photovoltaics (OPVs) due to the dilution effect. While the compromise between the charge generation and recombination remains a challenge. Here, a mixed diluent strategy for further improving the device efficiency of OPV is proposed. Specifically, the high-performance OPV system with a polymer donor, i.e., PM6, and a nonfullerene acceptor (NFA), i.e., BTP-eC9, is diluted by the mixed diluents, which involve a high bandgap NFA of BTP-S17 and a low bandgap NFA of BTP-S16 (similar with that of the BTP-eC9). The BTP-S17 of better miscibility with BTP-eC9 can dramatically enhance the open-circuit voltage (VOC ), while the BTP-S16 maximizes the charge generation or the short-circuit current density (JSC ). The interplay of BTP-17 and BTP-S16 enables better compromise between charge generation and recombination, thus leading to a high device performance of 19.76% (certified 19.41%), which is the best among single-junction OPVs. Further analysis on carrier dynamics validates the efficacy of mixed diluents for balancing charge generation and recombination, which can be further attributed to the more diverse energetic landscapes and improved morphology. Therefore, this work provides an effective strategy for high-performance OPV for further commercialization.

Multiphase Morphology with Enhanced Carrier Lifetime via Quaternary Strategy Enables High-Efficiency, Thick-Film, and Large-Area Organic Photovoltaics.

With the continuous breakthrough of the efficiency of organic photovoltaics (OPVs), their practical applications are on the agenda. However, the thickness tolerance and upscaling in recently reported high-efficiency devices remains challenging. In this work, the multiphase morphology and desired carrier behaviors are realized by utilizing a quaternary strategy. Notably, the exciton separation, carrier mobility, and carrier lifetime are enhanced significantly, the carrier recombination and the energy loss (Eloss ) are reduced, thus beneficial for a higher short-circuit density (JSC ), fill factor (FF), and open-circuit voltage (VOC ) of the quaternary system. Moreover, the intermixing-phase size is optimized, which is favorable for constructing the thick-film and large-area devices. Finally, the device with a 110 nm-thick active layer shows an outstanding power conversion efficiency (PCE) of 19.32% (certified 19.35%). Furthermore, the large-area (1.05 and 72.25 cm2 ) devices with 110 nm thickness present PCEs of 18.25% and 12.20%, and the device with a 305 nm-thick film (0.0473 cm2 ) delivers a PCE of 17.55%, which are among the highest values reported. The work demonstrates the potential of the quaternary strategy for large-area and thick-film OPVs and promotes the practical application of OPVs in the future.

Achieving and Understanding of Highly Efficient Ternary Organic Photovoltaics: From Morphology and Energy Loss to Working Mechanism.

Ternary strategy, adding an additional donor (D) or acceptor (A) into conventional binary D:A blend, has shown great potential in improving photovoltaic performances of organic photovoltaics (OPVs) for practical applications. Herein, this review is presented on how efficient ternary OPVs are realized from the aspects of morphology, energy loss, and working mechanism. As to morphology, the role of third component on the formation of preferred alloy-like-phase and vertical-phase, which are driven by the miscibility tuning, is discussed. For energy loss, the effect of the third component on the luminescence enhancement and energetic disordering suppression, which lead to favorable increase of voltage, is presented. Regarding working mechanism, dilution effect and relationships between two acceptors or donor/acceptor, which explain the observed device parameters variations, are analyzed. Finally, some future directions concerning ternary OPVs are pointed out. Therefore, this review can provide a comprehensive understanding of working principles and effective routes for high-efficiency ternary systems, advancing the commercialization of OPVs.

Balancing the Selective Absorption and Photon-to-Electron Conversion for Semitransparent Organic Photovoltaics with 5.0% Light-Utilization Efficiency.

Efficiently converting invisible light while allowing full visible light transmission is key to achieving high-performance semitransparent organic photovoltaics (ST-OPVs). Here, a detailed balance strategy is explored to optimize the ST-OPV via taking both absorption and carrier dynamics into consideration. Based on this principle, comprehensive optimizations are carried out, including a ternary strategy, donor:acceptor blend ratio, thickness, antireflection, etc., to compromise the invisible energy conversion and visible transmission for high-performance ST-OPVs. As a result, the opaque OPV device exhibits a champion power conversion efficiency of 19.35% (certificated 19.07%), and most strikingly, the best ST-OPV shows a remarkably high light-utilization efficiency of 5.0%, where the efficiency and the average visible transmission are 12.95% and 38.67%, respectively. An efficiency of 12.09% is achieved on the upscaled device with an area of 1.05 cm2 , demonstrating its promise for large-area fabrication. These results are among the best values for ST-OPVs. Besides, it is demonstrated that the ST-OPV exhibits good infrared light-reflection capability for thermal control. This work provides a rational design of balancing the absorbing selectivity and photon-to-electron conversion for high-performance ST-OPVs, and may pave the way toward the practical application of solar windows.

Asymmetric electron acceptor enables highly luminescent organic solar cells with certified efficiency over 18.

Enhancing the luminescence property without sacrificing the charge collection is one key to high-performance organic solar cells (OSCs), while limited by the severe non-radiative charge recombination. Here, we demonstrate efficient OSCs with high luminescence via the design and synthesis of an asymmetric non-fullerene acceptor, BO-5Cl. Blending BO-5Cl with the PM6 donor leads to a record-high electroluminescence external quantum efficiency of 0.1%, which results in a low non-radiative voltage loss of 0.178 eV and a power conversion efficiency (PCE) over 15%. Importantly, incorporating BO-5Cl as the third component into a widely-studied donor:acceptor (D:A) blend, PM6:BO-4Cl, allows device displaying a high certified PCE of 18.2%. Our joint experimental and theoretical studies unveil that more diverse D:A interfacial conformations formed by asymmetric acceptor induce optimized blend interfacial energetics, which contributes to the improved device performance via balancing charge generation and recombination.

High-Efficiency ITO-Free Organic Photovoltaics with Superior Flexibility and Upscalability.

Developing indium-tin-oxide (ITO)-free flexible organic photovoltaics (OPVs) with upscaling capacity is of great significance for practical applications of OPVs. Unfortunately, the efficiencies of the corresponding devices lag far behind those of ITO-based rigid small-area counterparts. To address this issue, an advanced device configuration is designed and fabricated featuring a top-illuminated structure with ultrathin Ag as the transparent electrode. First, a conjugated polyelectrolyte layer, i.e., PCP-Li, is inserted to effectively connect the bottom Ag anode and the hole transport layer, achieving good photon to electron conversion. Second, charge collecting grids are deposited to suppress the increased resistance loss with the upscaling of the device area, realizing almost full retention of device efficiency from 0.06 to 1 cm2 . Third, the designed device delivers the best efficiency of 15.56% with the area of 1 cm2 on polyimide substrate, representing as the record among the ITO-free, large-area, flexible OPVs. Interestingly, the device exhibits no degradation after 100 000 bending cycles with a radius of 4 mm, which is the best result for flexible OPVs. This work provides insight into device structure design and optimization for OPVs with high efficiency, low cost, superior flexibility, and upscaling capacity, indicating the potential for the future commercialization of OPVs.

Dilution effect for highly efficient multiple-component organic solar cells.

Although the multiple-component (MC) blend strategy has been frequently used as a very effective way to improve the performance of organic solar cells (OSCs), there is a strong need to understand the fundamental working mechanism and material selection rule for achieving optimal MC-OSCs. Here we present the 'dilution effect' as the mechanism for MC-OSCs, where two highly miscible components are molecularly intermixed. Contrary to the aggregation-induced non-radiative decay, the dilution effect enables higher luminescence quantum efficiencies and open-circuit voltages (VOC) in MC-OSCs via suppressed electron-vibration coupling. The continuously broadened bandgap together with reduced electron-vibration coupling also explains the composition-dependent VOC in ternary blends well. Moreover, we show that electrons can transfer between different acceptors, depending on the energy offset between them, which contributes to the largely unperturbed charge transport and high fill factors in MC-OSCs. The discovery of the dilution effect enables the demonstration of a high power conversion efficiency of 18.31% in an MC-OSC.

Complete mitogenome of Treron sphenurus (Aves, Columbiformes): the first representative from the genus Treron, genomic comparisons and phylogenetic analysis of Columbidae.

The wedge-tailed green pigeon (Treron sphenurus) has a protective value in the evolution of the family Columbidae. In this study, the complete mitogenome of T. sphenurus from Baise City, China, which represents the first sequenced species of the genus Treron in Tribe Treronini, is reported. This was accomplished using PCR-based methods and a primer-walking sequencing strategy with genus-specific primers. The mitogenome was found to be 18,919 bp in length comprising 37 genes, including 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and one control region. In terms of structure and composition, many similarities were found between the T. sphenurus and Hemiphaga novaeseelandiae (New Zealand pigeon) mitogenomes. This was further supported by phylogenetic analysis showing that T. sphenurus has a close evolutionary relationship with H. novaeseelandiae. The complete mitogenome of T. sphenurus reported here is expected to provide valuable molecular information for further studies on the phylogeny of the genus Treron and for analyses of the taxonomic status of the family Columbidae.

Layer-by-Layer Processed Ternary Organic Photovoltaics with Efficiency over 18.

Obtaining a finely tuned morphology of the active layer to facilitate both charge generation and charge extraction has long been the goal in the field of organic photovoltaics (OPVs). Here, a solution to resolve the above challenge via synergistically combining the layer-by-layer (LbL) procedure and the ternary strategy is proposed and demonstrated. By adding an asymmetric electron acceptor, BTP-S2, with lower miscibility to the binary donor:acceptor host of PM6:BO-4Cl, vertical phase distribution can be formed with donor-enrichment at the anode and acceptor-enrichment at the cathode in OPV devices during the LbL processing. In contrast, LbL-type binary OPVs based on PM6:BO-4Cl still show bulk-heterojunction like morphology. The formation of the vertical phase distribution can not only reduce charge recombination but also promote charge collection, thus enhancing the photocurrent and fill factor in LbL-type ternary OPVs. Consequently, LbL-type ternary OPVs exhibit the best efficiency of 18.16% (certified: 17.8%), which is among the highest values reported to date for OPVs. The work provides a facile and effective approach for achieving high-efficiency OPVs with expected morphologies, and demonstrates the LbL-type ternary strategy as being a promising procedure in fabricating OPV devices from the present laboratory study to future industrial production.

Simple Near-Infrared Electron Acceptors for Efficient Photovoltaics and Sensitive Photodetectors.

Although promising progress has been made in near-infrared (NIR) electron acceptors for broadening photoresponse of optoelectronics, there are still strong needs for efficient NIR materials with low synthetic complexities. In this work, three simple NIR acceptors are developed with absorption up to 1000 nm and possessing the same dithiophene cores with varied heteroatom linkages to carbon (C) atom for W1, to silicon (Si) for W2, and to nitrogen (N) for W3. It is found that the tuning of only one atom for simple acceptors can surprisingly lead to a large difference in photoelectric properties and solid stacking, as well as the performance in optoelectronics. Although quite simple, these electron acceptors, especially W1 (C), can also perform quite efficiently as organic photovoltaics (OPVs) as well as sensitive organic photodetectors (OPDs) when blended with PTB7-Th polymer. It is worthy to note that, among the representative NIR acceptors with over 950 nm absorption, W1 possesses one of the best figure-of-merit when considering the photoelectric performance versus synthetic complexity of materials. As a result, the PTB7-Th:W1-based OPDs reach a fast temporal response, ultralow-light intensity detection of 1.70 × 10-11 W·cm-2, and a high specific detectivity of 4.28 × 1012 cm·Hz1/2·W-1 at 830 nm, representing a highly sensitive self-powered OPD approach the commercial broadband silicon detectors. These simple structure materials provide a potential example for further application of NIR electron acceptor.

Near-Infrared Electron Acceptors with Unfused Architecture for Efficient Organic Solar Cells.

The absorption of nonfullerene acceptors (NFAs) at near-infrared (NIR) regions is crucial for obtaining high current densities in organic solar cells (OSCs). Herein, two narrow-band gap NFAs with unfused backbones possessing broad (600-900 nm) and strong absorption are developed by the conjugation of a benzothiadiazole core to halogenated end groups through a cyclopentadithiophene bridge. Compared with the fluorinated counterpart BCDT-4F, the chlorinated NFA BCDT-4Cl shows stronger J-aggregation and closer molecular packing, leading to an optimized blend morphology when paired with the polymer donor, PBDB-T. Thus, an obvious improvement in external quantum efficiency response was obtained for BCDT-4Cl-based OSCs, presenting a higher efficiency of 12.10% than those (9.65%) based on BCDT-4F. This work provides a design strategy for NIR acceptors in the combination of electron-deficient core and halogenated terminal in unfused backbones, which results in not only fine-tuning the optoelectronic properties but also simplifying the synthetic complexities of molecules.