Search

Non‐fullerene acceptors have shown great promise for organic solar cells (OSCs). However, challenges in achieving high efficiency molecular system with conformational unicity and effective molecular stacking remain. In this study, we present a new design of non‐fused tetrathiophene acceptor R4T‐1 via employing the encapsulation of tetrathiophene with macrocyclic ring. The single crystal structure analysis reveals that cyclic alkyl side chains can perfectly encapsulate the central part of molecule and generate a conformational stable and planar molecular backbone. Whereas, the control 4T‐5 without the encapsulation restriction displays cis‐ and twisted conformation. As a result, R4T‐1 based OSCs achieved an outstanding power conversion efficiency (PCE) exceeding 15.10 % with a high short‐circuit current density (Jsc) of 25.48 mA/cm2, which is significantly improved by ≈30 % in relative to that of the control. Our findings demonstrate that the macrocyclic encapsulation strategy could assist fully non‐fused electron acceptors (FNEAs) to achieve a high photovoltaic performance and pave a new way for FNEAs design. [ABSTRACT FROM AUTHOR]

The electron transport layer (ETL) is a critical component in achieving high device performance and stability in organic solar cells. Conjugated polyelectrolytes (CPEs) have become an attractive alternative due to film‐forming properties and ease of preparation. However, p‐type CPEs generally exhibit poor charge mobility and conductivity, incorporation of electron‐withdrawing units forming alternated D‐A conjugated backbone can make up for these deficiencies. Herein, the ratio of electron withdrawing moieties are further increased and two poly(A1‐alt‐A2) typed PIIDNDI‐Br and PDPPNDI‐Br based on the combination of naphthalene diimide (NDI) with isoindigo (IID) or diketopyrrolopyrrole (DPP) via direct arylation polycondensation are synthesized. These CPEs possess excellent alcohol solubility, a suitable lowest unocuppied molecular orbital energy level, and work function tunability. Surprisingly, the incorporation of IID and DPP units generate distinct self‐doping behaviors, which are confirmed by UV–vis absorption and ESR spectra. However, no matter doped or undoped, both CPEs present better charge‐transporting properties and conductivity when utilized as ETLs. The PIIDNDI‐Br and PDPPNDI‐Br display good universal compatibility with the blend of PM6:Y6 and PM6:L8‐BO, and PCEs of 18.32% and 18.36% are obtained, respectively, which also present excellent storage stability. In short, the combination of two different acceptors demonstrates an efficient strategy to design highly efficient ETLs for high performance photovoltaic devices. [ABSTRACT FROM AUTHOR]

Colorectal cancer (CRC) is one of the most common gastrointestinal malignancies. There are few recurrence risk signatures for CRC patients. Single-cell RNA-sequencing (scRNA-seq) provides a high-resolution platform for prognostic signature detection. However, scRNA-seq is not practical in large cohorts due to its high cost and most single-cell experiments lack clinical phenotype information. Few studies have been reported to use external bulk transcriptome with survival time to guide the detection of key cell subtypes in scRNA-seq data. We proposed scRankXMBD, a computational framework to prioritize prognostic-associated cell subpopulations based on within-cell relative expression orderings of gene pairs from single-cell transcriptomes. scRankXMBD achieves higher precision and concordance compared with five existing methods. Moreover, we developed single-cell gene pair signatures to predict recurrence risk for patients individually. Our work facilitates the application of the rank-based method in scRNA-seq data for prognostic biomarker discovery and precision oncology. scRankXMBD is available at https://github.com/xmuyulab/scRank-XMBD. (XMBD:Xiamen Big Data, a biomedical open software initiative in the National Institute for Data Science in Health and Medicine, Xiamen University, China.) [ABSTRACT FROM AUTHOR]

Fully non-fused electron acceptors (FNEAs) have shown a promising prospect for commercial applications of organic solar cells (OSCs) due to their simple structures and low costs. Herein, two terthiophene-based NFEAs 3T-1 and 3T-2 were exploited from a single thiophene ring as the starting material. Octyl substituted 3T-1 exhibits strong crystallinity, poor miscibility, and forms large aggregates when blending with polymer D18, leading to an inferior power conversion efficiency (PCE). While 2-ethylhexyl substituted 3T-2 possesses good solubility and enhanced compatibility with polymer D18, the blend film exhibits an appropriate morphology, face-on molecular orientation, and efficient charge transport. As a result, the as-cast device based on 3T-2 exhibits a significantly enhanced PCE of 11.12% processed by non-halogenated o-xylene as the solvent, which is the highest value of terthiophene based FNEAs for OSCs so far. Our work provides insight into molecular design of FNEAs for high-performance OSCs. [ABSTRACT FROM AUTHOR]

The power conversion efficiency of polythiophene organic solar cells is constantly refreshed. Despite the renewed device efficiency, very few efforts have been devoted to understanding how the type of electron acceptor alters the photovoltaic and mechanical properties of these low‐cost solar cells. Herein, the authors conduct a thorough investigation of photovoltaic and mechanical characteristics of a simple yet less‐explored polythiophene, namely poly(3‐pentylthiophene) (P3PT), in three different types of organic solar cells, where ZY‐4Cl, PC71BM, and N2200 are employed as three representative acceptors, respectively. Compared with the reference poly(3‐hexylthiophene) (P3HT)‐based solar cells, P3PT‐based devices, all perform more efficiently. Particularly, the P3PT:ZY‐4Cl blend exhibits the highest efficiency (ca. 10%) among the six combinations and outperforms the prior top‐performance system P3HT:ZY‐4Cl. Furthermore, the blend films based on N2200 exhibit a high crack‐onset strain of ∼38% on average, which is approximately 15‐ and 17‐times higher than those of ZY‐4Cl and PC71BM, respectively. The microstructural origins for the above difference are well elucidated by detailed grazing incidence X‐ray scattering and microscopy analysis. This work not only underlines the potential of P3PT in prolific solar cell research but also demonstrates the superior tensile properties of polythiophene‐based all‐polymer blends for the preparation of stretchable solar cells. [ABSTRACT FROM AUTHOR]

It has been reported that the output performance of a triboelectric nanogenerator (TENG) can be enhanced by applying light; however, the coupling mechanism between photogenerated carriers and triboelectric charges is still not well explained. Here, we propose a light-enhanced TENG based on a P3HT:PC61BM active blend layer, which processes dual functions of the photoelectric effect and the triboelectric effect. The open-circuit voltage, short circuit current, and amount of transferred charges for the TENG were enhanced by 63%, 76%, and 127%, respectively, after illumination under the white light condition. Moreover, we have investigated the interaction between the triboelectric charges and the photogenerated carriers to further explore the coupling mechanism between the triboelectric and photoelectric effects. Both Kelvin probe force microscopy and conductive atomic force microscopy demonstrate that the photogenerated carriers produced by the P3HT:PC61BM active blend layer can improve the surface triboelectric charge density. More interestingly, the transient absorption spectrum indicates that the electrostatic field induced by triboelectric charges contributes to the dissociation of excitons. In other words, there exists a beneficial promoting effect between the triboelectric charges and the photogenerated carriers during the operation of the light-enhanced TENG. This work provides an important guideline for the design and performance improvement of the hybrid TENG that captures both mechanical energy and light energy simultaneously. [ABSTRACT FROM AUTHOR]

A series of tetrathiophene‐based fully non‐fused ring acceptors (4T‐1, 4T‐2, 4T‐3, and 4T‐4), which can be paired with the star donor polymer PBDB‐T to fabricate highly efficient organic solar cells are developed. Tailoring the size of lateral chains can tune the solubility and packing mode of acceptor molecules in neat and blend films. It is found that the incorporation of 2‐ethylhexyl chains can effectively change the compatibility with the donor polymer PBDB‐T, and an encouraging power conversion efficiency of 10.15% is accomplished by 4T‐3‐based organic solar cells. It also presents good compatibility with the other polymer donor and an even higher power conversion efficiency (PCE) of 12.04% is achieved based on D18:4T‐3 blend, which is the champion PCE for the fully non‐fused acceptors. Importantly, these inexpensive tetrathiophene fully non‐fused ring acceptors provide cost‐effective photovoltaic performance. The results demonstrate a high photovoltaic performance from synthetically inexpensive materials could be achieved by the rational design of non‐fused ring acceptor molecules. [ABSTRACT FROM AUTHOR]

Organic semiconductors including conjugated polymers and small molecules can be applied in many fields due to their unique advantages, such as light weight, solution processability, easy functionalization etc. During the past ten years, we mainly focused on the design and synthesis of conjugated polymer donor materials and small molecular acceptor materials for organic solar cells and hole transport materials for perovskite solar cells. To obtain planar conjugated polymers, low cost small molecular acceptors, and dopant-free hole transport polymers, we adopted intramolecular noncovalent interactions (INCIs) as the design strategy. In this brief review, we will demonstrate that the INCI strategy is very efficient in the design of high performance photovoltaic materials. [ABSTRACT FROM AUTHOR]

Molecular orientation is one of the key parameters that would greatly influence the charge transportation in sandwich-type organic photovoltaic devices. Herein, two new A–π–D–π–A type acceptor molecules Ph-DTDPo-OTE and Ph-DTDPo-TE are designed and synthesized based on a 2H-pyran derived ladder-type dipyran core (DTDPo). A branched 2-ethylhexyloxy chain is utilized to replace the linear hexyloxy one so as to improve the solubility and blend morphology. It's interesting that the dominant edge-on orientation for Ph-DTDPo-OTE could be converted to the favorite face-on packing when the alkyloxy chains are replaced by alkyl ones. The desired molecular orientations of both Ph-DTDPo-TE and PBDB-T could guarantee the efficient charge transportation. In addition, good miscibility and interpenetrated fibrils have been observed in the blend of Ph-DTDPo-TE:PBDB-T by both surficial and in-depth morphology characterization experiments. Finally, a high PCE of 12.21% (Voc = 0.82 V, Jsc = 20.83 mA cm−2 and FF = 71.14%) is achieved for Ph-DTDPo-TE , which is one of the highest values for binary OSCs based on a pyran comprising acceptor. Our research demonstrates that appropriate side chain engineering at the π-bridge is an effective strategy to regulate molecular orientations and the morphology of blend films. [ABSTRACT FROM AUTHOR]

The π–π stacking of terminal electron-deficient groups is known to support the main charge transport pathway in acceptor–donor–acceptor type fused-ring electron acceptors (FREAs). Interactions between terminal groups influence molecular stacking and ultimate photovoltaic performances. Herein, we designed two novel asymmetric FREAs bearing different polar terminal groups via a facile stepwise Knoevenagel condensation. The combination of two terminal groups with differing polarities in a single molecule fine-tuned the absorption and energy levels. Furthermore, the different terminal groups induced a permanent dipole moment over the whole molecule with regional dipole moments at the end regions. These effects enabled control over intermolecular interactions, crystallization properties, and the blended microscopic morphology. Single-junction solar cells based on the asymmetric a-IT-2OM in combination with the widely used polymer donor PBDB-T yielded power conversion efficiencies (PCEs) as high as 12.07%, which represents a 30%-increase compared with that of the control device. Notably, devices based on PBDB-T/a-IT-2OM retained high PCEs greater than 11% for active layer thicknesses up to 200 nm; PCEs of approximately 9% were maintained even at a thickness of 450 nm. These findings offer a route to high performance FREA molecules for thick-film solar cell devices and also provide a novel asymmetric molecular design strategy. [ABSTRACT FROM AUTHOR]

We designed and synthesized three PDI derivatives (PDI-II, PDI-III and PDI-IV). All these acceptor molecules have a central benzene core and the PDI units are linked to the central benzene core by an acetylene spacer. PDI-II is a linear molecule, which bears two flanked PDI units, PDI-III is a c3-symmetrical star-shaped molecule with three peripheral PDI units, and PDI-IV is a star-shaped molecule with four PDI units linked to the 1,2,4,5-positions of the central benzene core. These absorption features indicated that the PDI units in PDI-II and PDI-III are planar, whereas the PDI units in PDI-IV are twisted due to the steric crowding. Compared with the linear PDI-II, the star-shape could effectively prevent PDI-III and PDI-IV from forming large aggregates when blended with the donor polymer PBDB-T. PBDB-T:PDI-II, PBDB-T:PDI-III and PBDB-T:PDI-IV based OSCs gave power conversion efficiencies (PCEs) of 3.05%, 6.00% and 1.04%, respectively. The big differences in electron mobility and PCE for PDI-III and PDI-IV are probably due to the fact that the PDI units in PDI-III are planar and those in PDI-IV are twisted. [ABSTRACT FROM AUTHOR]

Abstract: Molecular engineering of nonfullerene acceptors (NFAs) plays a vital role in the development of organic photovoltaics. Oxygen as an electron donating atom is incorporated into the NFA system as alkoxyl forms at central, terminal, or central conjugated moieties due to the tunability at structural conformation, solubility, electron donating ability, absorption, energy levels, etc. In this work, a novel dipyran‐based ladder‐type building block (Ph‐DTDP), which possesses two oxygen atoms in the conjugated skeleton, is designed and facilely synthesized. It is applied as the donor core for the acceptor–donor–acceptor‐type NFA design and such functionalized‐O efficiently enhances the electron donating ability, lowers the band gap, redshifts and extends the absorption spectra. In addition, the π‐bridge effects are considered as well. Photovoltaic performances are systematically investigated and a high power conversion efficiency of 9.21% can be afforded with an energy loss of 0.57 eV. Meanwhile, the morphologies as well as the carrier mobilities of the blend films are studied to assist further understanding of the structure–property relationships. Overall, the study in this work provides a new promising ladder‐type dipyran building block and brings in a novel way to use oxygen in NFA molecular structure design. [ABSTRACT FROM AUTHOR]

Three planar nonfullerene acceptors (FTIC-C8C6, FTIC-C6C6 and FTIC-C6C8) comprising a central fluorenedicyclopentathiophene (FT) core and two 2-methylene-(3-(1,1-dicyanomethylene)-indanone) terminal groups are designed and synthesized. The coplanarity of the molecular backbone can be maintained through a locked conformation via intramolecular noncovalent interactions. The solubility of these nonfullerene acceptors is very good because the FT core can bear enough flexible aliphatic side-chain substitutions. Thus, the dilemma of the planarity–solubility tradeoff can be minimized. Through changing the length of the six flexible aliphatic side chains at the central FT core, we can easily adjust the π–π interactions of nonfullerene acceptors and optimize the nanoscale morphology of the photoactive layers. Among these three small molecular acceptors, FTIC-C6C8 based active layers show the best morphology together with the highest electron and hole mobility. These inherent advantages of FTIC-C6C8 guarantee it a high power conversion efficiency of 11.12% when used in non-fullerene polymer solar cells with a wide-bandgap polymer donor PBDB-T. Our results provide an appropriate molecular design strategy for building high-performance nonfullerene acceptors and show that optimizing alkyl-side chains is a very effective way to further improve the photovoltaic performance of devices. [ABSTRACT FROM AUTHOR]

• Investigated the capability of an array of sweeping jet actuators (SJAs) in the control of a large-scale S-shaped duct at inlet Ma = 0.4. • Qualitatively and quantitatively evaluated the flow control effects of SJAs. • The SJAs effectively suppressed the flow separation and distortion. • Absolute pressure recovery at the upper region of AIP increased nearly 5%. • Mean value and RMSE of cross-flow velocity at AIP declined 54.9% and 48.1%, respectively. An experimental study was conducted on the flow control capability of sweeping jet actuators (SJAs) in an aggressive offset S-shaped duct with an inlet Mach number of 0.4. The SJAs were placed in two different spacing arrangements to suppress flow separation in the duct and flow distortion at the aerodynamic interface plane (AIP). Multiple measurements were taken, including surface oil flow visualization, steady pressure on the wall surface, five-hole probe pressure, and velocity at the AIP. For the baseline case without control, the surface oil flow visualization and pressure measurement results clearly reflected the three-dimensional flow separation characteristics in the duct. In the controlled cases, the streamwise surface pressure coefficient distribution showed that SJAs can effectively suppress the flow separation. At a spacing ratio of 8.13 and an excitation pressure of 250 kPa, the inflection point of the pressure coefficient C p was completely eliminated. As a result, the absolute pressure recovery at the upper region of the AIP increased by nearly 5%, and the mean value and RMSE of the cross-flow velocity declined by 54.9% and 48.1%, respectively. [ABSTRACT FROM AUTHOR]