Non-Fully Conjugated Photovoltaic Materials with Y-Series Acceptor Backbone for High-Performance Organic Solar Cells

In the last few years,organic solar cells(OSCs)have made significant progress in photovoltaic performance,mainly due to the innovative development of active layer materials,especially Y-series and related derivatives as acceptors which have become the key factor that boosts the power conversion efficiency.Recently,to achieve high-performance OSCs,an emerging molecular design strategy of applying flexible alkyl units as linkers to construct non-fully conjugated acceptors has been developed and addressed great attention.This review highlights the non-fully conjugated photovoltaic materials with Y-series backbone that enable high-performance OSCs.Impressive OSCs have been achieved by some representative non-fully conjugated material systems.The related molecular design strategies are discussed in detail.Finally,a brief summary and future prospect are provided in advancing the non-fully conjugated photovoltaic materials with Y-series backbone towards the brighter future.

Functional nanoemulsions: Controllable low-energy nanoemulsification and advanced biomedical application

Nanoemulsions are widely used as advanced pharmaceutical delivery systems in biomedical field, due to their high encapsulation efficiency and good therapy efficacy.Nanoemulsification techniques that produce nanoemulsions with controllable sizes and compositions are promising for creating advanced nanoemulsion systems for pharmaceutical delivery.This review summarizes recent advances on low-energy emulsification techniques for producing nanoemulsions, and the use of these nanoemulsions as advanced pharmaceutical delivery systems and as templates to create drug-loaded functional particles for biomedical application.First, nanoemulsification techniques that utilize elaborate interfacial physics/chemistry and micro-/nano-fluidics, featured with relatively-low energy input, to produce nanoemulsions with controllable sizes and compositions, are introduced.Uses of these nanoemulsions to create nanoemulsionincorporated milli-particles, drug-loaded nanoparticles and nanoparticle-incorporated microparticles with sizes ranging from several millimeters to sub-10 nm are emphasized.Flexible and efficient use of the nanoemulsions, functional nanoparticles and milli-/micro-particles integrated with nanoemulsions or nanoparticles for advanced pharmaceutical delivery in biomedical field are highlighted, with focus on how the interplay between their sizes and compositions achieve desired pharmaceutical-delivery performances.Finally, perspectives on further advances on the controllable production of nanoemulsions are provided.

A Non-Halogenated Polymer Donor Based on Imide Unit for Organic Solar Cells with Efficiency Nearly 16%

Comprehensive Summary,Non-halogenated polymers have great potential in the commercialization of organic solar cells(OSCs)due to their advantages in the manufacturing process.However,high-performance donor polymers are limited to a small amount of building blocks.Herein,we utilize as building block 4H-dithieno[3,2-e:2',3'-g]isoindole-4,6(5H)-dione(DTID)to design and synthesize a relevant non-halogenated polymer PBTID for active layers in OSCs.PBTID exhibits a strong absorption in the wavelength range of 400—600 nm with a distinctly wide optical bandgap of 2.06 eV,a low-lying highest occupied molecular orbital(HOMO)energy level of−5.53 eV.In addition,this polymer has a very strong aggregation effect in solution and could form nanoscale fibrils in the neat film.Consequently,when blended with the non-fullerene acceptor Y6,the devices achieve a prominent PCE of 15.8%with a high Voc of 0.87 V.The Voc and PCE values are one of the highest values in the non-halogenated polymer donor-based OSCs reported to date.

π-Extended End Groups Enable High-Performance All-Polymer Solar Cells with Near-Infrared Absorption

Narrow-bandgap n-type polymers are essential for advancing the development of all-polymer solar cells(all-PSCs).Herein,we developed a novel polymer acceptor PNT withπ-extended 2-(3-oxo-2,3-dihydro-1H-cyclopenta[b]naphthalen-1-ylidene)malononitrile(CPNM)end groups.Compared to commonly used 2-(3-oxo-2,3-dihydro-1H-cyclopenta[b]naphthalen-1ylidene)malononitrile(IC)units,CPNM units have a further extended fused ring,providing the PNT polymer with extended absorption into the near-IR region(903 nm)and exhibiting a narrow optical bandgap(1.37 eV).Furthermore,PNT exhibits a high electron mobility(6.79×10^(−4) cm^(2)·V^(−1)·S^(−1))and a relatively high-lying lowest unoccupied molecular orbital(LUMO)energy level of−3.80 eV.When blended with PBDB-T,all-PSC achieves a power conversion efficiency(PCE)of 13.7%and a high short-circuit current density(JSC)of 24.4 mA·cm^(−2),mainly attributed to broad absorption(600—900 nm)and efficient charge separation and collection.Our study provides a promising polymer acceptor for all-PSCs and demonstrates thatπ-extended CPNM units are important to achieve high-performance for all-PSCs.

An asymmetric non-fused electron-deficient building block for low-cost polymer acceptor in all-polymer solar cells

The development of polymerized fused-ring small molecule acceptors(FRA-PAs) has boosted the performance of all-polymer solar cells(all-PSCs).However,these FRA-PAs suffer from lengthy synthesis steps and high production costs due to the high degree of synthetic complexity for fused-ring small molecule acceptors(FRAs).Furthermore,most FRA-PAs exhibit strong batch-to-batch variation,limiting further industrial applications.Herein,we designed and synthesized asymmetric non-fused electron-deficient building block TIC-Br with a simple structure(only three synthetic steps),showing a planar configuration,excellent electron affinity,and large dipole moment.A simple polymer acceptor PTIB was further developed by polymerization of TIC-Br and sensitized fluorinated-thienyl benzodithiophene(BDT-TF-Sn).PTIB exhibits a broad absorption from 300 to 800 nm,a suitable lowest unoccupied molecular orbital(LUMO) energy level of-3.86 e V,and moderate electron mobility(1.02×10^(-4)cm^(2)V^(-1)s^(-1)).When matched with PM6,the device achieved the best PCE of 10.11%with a high V_(OC) of 0.97 V,which is one of the highest among those reported all-PSCs.More importantly,PTIB exhibits a lower synthetic complexity index(SC=35.0%)and higher figure-of-merit values(FOM=29.0%) than all the reported high-performance PAs.The polymer also exhibits excellent batch-to-batch reproducibility and great potential for scale-up fabrication.This study indicates that TIC-Br is a promising building block for constructing low-cost polymer acceptors for large-scale applications in all-PSCs.

Improving open-circuit voltage by a chlorinated polymer donor endows binary organic solar cells efficiencies over 17%

Power conversion efficiency(PCE)of single-junction polymer solar cells(PSCs)has made a remarkable breakthrough recently.Plenty of work was reported to achieve PCEs higher than 16%derived from the PM6:Y6 binary system.To further increase the PCEs of binary OSCs incorporating small molecular acceptor(SMA)Y6,we substituted PM6 with PM7 due to the deeper highest occupied molecular orbital(HOMO)of PM7.Consequently,the PM7:Y6 has achieved PCEs as high as 17.0%by the hotcast method,due to the improved open-circuit voltage(VOC).Compared with PM6,the lower HOMO of PM7 increases the gap between ELUMO-donor and EHOMO-acceptor,which is proportional to VOC.This research provides a high PCE for single-junction binary PSCs,which is meaningful for device fabrication related to PM7 and commercialization of PSCs.

11.2% Efficiency all-polymer solar cells with high open-circuit voltage

Herein,we fabricated all-polymer solar cells(all-PSCs)based on a fluorinated wide-bandgap p-type conjugated polymer PM6 as the donor,and a narrow bandgap n-type conjugated polymer PZ1 as the acceptor.In addition to the complementary absorption and matching energy levels,the optimized blend films possess high cystallinity,predominantly face-on stacking,and a suitable phase separated morphology.With this active layer,the devices exhibited a high Vocof 0.96 V,a superior Jscof 17.1 mA cm^-2,a fine fill factor(FF)of 68.2%,and thus an excellent power conversion efficiency(PCE)of 11.2%,which is the highest value reported to date for single-junction all-PSCs.Furthermore,the devices showed good storage stability.After 80 d of storage in the N2-filled glovebox,the PCE still remained over 90%of the original value.Large-area devices(1.1 cm^2)also demonstrated an outstanding performance with a PCE of 9.2%,among the highest values for the reported large-area all-PSCs.These results indicate that the PM6:PZ1 blend is a promising candidate for scale-up production of large area high-performance all-PSCs.

气泡驱动型微马达功能材料可控制备研究新进展

气泡驱动型微马达功能材料由于能分解化学物质产生气泡,从而驱动自身运动、强化流体混合与传质,因此在污染治理、药物传送、环境监测、物质分离以及疾病诊断等方面展现出了独特的优势和极大的应用前景.制备该微马达功能材料的关键在于如何在其中可控构建非对称的结构.本文主要介绍了近年来可控制备具有多样化结构和功能的气泡驱动型微马达功能材料的研究新进展,着重介绍了如何基于非对称结构的构建来设计和制备颗粒状和管状等结构的新型微马达功能材料,以及如何在微马达中巧妙整合多样化功能组分和结构来实现其多功能化,以期为创新设计和可控制备具有独特结构和先进功能的气泡驱动型微马达功能材料提供新的途径和指导.

A Non-Fullerene Acceptor with Chlorinated Thienyl Conjugated Side Chains for High-Performance Polymer Solar Cells via Toluene Processing

Small molecular acceptors(SMAs)BTC-2F and BTH-2F,based on heptacyclic benzodi(cyclopentadithiophene)electron-donating core(CBT)with chlorinated-thienyl conjugated and thienyl conjugated side chains,respectively,are designed and synthesized.Compared with non-chlorine acceptor BTH-2F,BTC-2F exhibits slightly blue-shifted absorption spectra,similar the lowest unoccupied molecular orbital(LUMO)(-3.91 eV);deeper highest occupied molecular orbital(HOMO)energy level and higher electron mobility than that of BTH-2F.PM6,a wide bandgap polymer,is selected as the donor material to construct bulk heterojunction polymer solar cells processed with nonhalogenated solvent toluene.The optimized PM6:BTC-2F-based device presents a 12.9%power conversion efficiency(PCE),while the PCE of PM6:BTH-2F-based device is only 11.3%.The results suggest that it is an effective strategy to optimize the photoelectric properties of SMAs by incorporating chlorine atom into the conjugated side chains.

Synergistic effect of fluorination on both donor and acceptor materials for high performance non-fullerene polymer solar cells with 13.5% efficiency

A high performance polymer solar cells(PSCs) based on polymer donor PM6 containing fluorinated thienyl benzodithiophene unit and n-type organic semiconductor acceptor IT-4 F containing fluorinated end-groups were developed. In addition to complementary absorption spectra(300–830 nm) with IT-4 F, the PM6 also has a deep HOMO(the highest occupied molecular) level(-5.50 e V), which will lower the open-circuit voltage(V_(oc)) sacrifice and reduce the E_(loss) of the IT-4 F-based PSCs. Moreover, the strong crystallinity of PM6 is beneficial to form favorable blend morphology and hence to suppress recombination. As a result, in comparison with the PSCs based on a non-fluorinated D/A pair of PBDB-T:ITIC with a medium PCE of 11.2%, the PM6:IT-4 Fbased PSCs yielded an impressive PCE of 13.5% due to the synergistic effect of fluorination on both donor and acceptor, which is among the highest values recorded in the literatures for PSCs to date. Furthermore, a PCE of 12.2% was remained with the active layer thickness of up to 285 nm and a high PCE of 11.4% was also obtained with a large device area of 1 cm^2. In addition, the devices also showed good storage, thermal and illumination stabilities with respect to the efficiency. These results indicate that fluorination is an effective strategy to improve the photovoltaic performance of materials, as well as the both fluorinated donor and acceptor pair-PM6:IT-4 F is an ideal candidate for the large scale roll-to-roll production of efficient PSCs in the future.

Modulating Crystallinity and Miscibility via Side-chain Variation Enable High Performance All-Small-Molecule Organic Solar Cells

Side-chain engineering as one of the most important molecular design strategies has been widely used to improve photovoltaic effi-ciency of active layer materials.Herein,a series of acceptor-n-donor-n-acceptor typed small molecule(SM)-donors(SL1,SL2,SL3,and SL4),on the basis of high-performance SM-donor BTTzR(SL1)with thiazolo[5,4-d]thiazole as the n-bridging units and 3-butylrho-danine as the terminal electron-withdrawing groups,were designed and synthesized to study the effect of the side-chain substitu-tions of BDT-T on the photovoltaic performanee.

A Noncovalently Fused-Ring Asymmetric Electron Acceptor Enables Efficient Organic Solar Cells

Main observation and conclusion Recently,the asymmetric nonfullerene acceptors(NFAs)with acceptor-donor-acceptor(A-D-A)structure have been developed rapidly,especially for the modification of asymmetric core,asymmetric side chains and asymmetric end groups.In this work,a novel asymmetric A-D-π-A type NFA with a noncovalently fused-ring core named PIST-4F is synthesized,containing an indacenodithieno[3,2-b]dithiophene(IDT),two strong electron-withdrawing end groups and an alkylthio-substituted thiopheneπ-bridge.Benefiting from the S···S noncovalent interaction between the sulfur atom onπ-bridge and the adjacent thiophene in IDT,the PIST-4F presents nearly planar geometry and extended conjugated area,resulting in the optimized electronic properties,charge transport,and film morphology compared to the symmetric NFA PI-4F.As a result,PM6:PIST-4F-based devices achieve a higher power conversion efficiency(PCE)of 13.8%,while the PM6:PI-4F-based devices only show a PCE of 7.1%.Notably,the PM6:PIST-4F-based devices processed with nonhalogen solvent toluene exhibit an excellent PCE as high as 13.1%.These results indicate that PIST-4F is an effective acceptor for high-efficiency organic solar cells.

Tuning Aggregation Behavior of Polymer Donor via Molecular-Weight Control for Achieving 17.1%Efficiency Inverted Polymer Solar Cells

Main observation and conclusion Recently,the polymer solar cells(PSCs)based on the PM6 and small molecular acceptor(SMA)Y6 have attracted considerable attention in this community for their outstanding photovoltaic performance.

Controllable microfluidic strategies for fabricating microparticles using emulsions as templates

Microfluidic techniques provide flexible strategies for fabrication of uniform advanced microparticles with well-tailored sizes, shapes, structures, and functions from controllable emulsion templates. This review highlights recent progress on controllable synthesis of microparticles using versatile microfluidic emulsions as templates, First, highly controllable and scalable microfluidic techniques for the generation of defined emulsions are introduced. Versatile microfluidic strategies for fabricating microparticles from diverse controllable emulsion templates are then summarized, including solid microparticles with spher- ical, non-spherical, and Janus configurations, porous microparticles with flexible pore structures, and compartmental microparticles with controlled internals. Finally, the future development of microfluidic techniques for microparticle fabrication is briefly discussed.

Effect of Fluorination on the Photovoltaic Properties of Medium Bandgap Polymers for Polymer Solar Cells

Fluorination of conjugated polymers is one of the effective strategies to tune the molecular energy levels and morphology for high efficient polymer solar cells （PSCs）. Herein, two novel donor-acceptor conjugated polymers, PffBT and PBT, based on bis（3,5-bis（hexyloxy）phenyl）benzo[1,2- b：4,5-b＇]dithiophene and benzo[c][1,2,5]thiadiazole （BT） with or without fluorination, respectively, were synthesized, and their photovoltaic properties were compared. The polymer PffBT based on fluorinated BT showed lower frontier energy levels, improved polymer ordering, and a well-developed fibril structure in the blend with PC71BM. As a result, the PSCs based on PffBT/PC71BM exhibit a superior power conversion efficiency （PCE） of 8.6% versus 4.4% for PBT-based devices, due to a high space charge limit current （SCLC） hole mobility, mixed orientation of polymer crystals in the active layer, and low bimolecular recombination.

Achieving 16.68% efficiency ternary as-cast organic solar cells

State-of-the-art organic solar cells(OSCs)often require the use of high-boiling point additive or post-treatment such as temperature annealing and solvent vapor annealing to achieve the best efficiency.However,additives are not desirable in largescale industrial printing process,while post-treatment also increases the production cost.In this article,we report highly efficient ternary OSCs based on PM6:BTP-Cl Br1:BTP-2O-4Cl-C12(weight ratio=1:1:0.2),with 16.68%power conversion efficiency(PCE)for as-cast device,relatively close to its annealed counterpart(17.19%).Apart from obvious energy tuning effect and complementary absorption spectra,the improved PCE of ternary device is mainly attributed to improved morphological properties including the more favorable materials miscibility,crystallinity,domain size and vertical phase separation,which endorse suppressed recombination.The result of this work provides understanding and guidance for high-performance as-cast OSCs through the ternary strategy.