Highly efficient and stable organic solar cells with SnO_(2)electron transport layer enabled by UV-curing acrylate oligomers

The interfaces between the inorganic metal oxide and organic photoactive layer are of outmost importance for efficiency and stability in organic solar cells(OSCs).Tin oxide(SnO_(2))is one of the promising candidates for the electron transport layer(ETL)in high-performance inverted OSCs.When a solution-processed SnO_(2)ETL is employed,however,the presence of interfacial defects and suboptimal interfacial contact can lower the power conversion efficiency(PCE)and operational stability of OSCs.Herein,highly efficient and stable inverted OSCs by modification of the SnO_(2)surface with ultraviolet(UV)-curable acrylate oligomers(SAR and OCS)are demonstrated.The highest PCEs of 16.6%and 17.0%are achieved in PM6:Y6-BO OSCs with the SAR and OCS,respectively,outperforming a device with a bare SnO_(2)ETL(PCE 13.8%).The remarkable enhancement of PCEs is attributed to the optimized interfacial contact,leading to mitigated surface defects.More strikingly,improved light-soaking and thermal stability strongly correlated with the interfacial defects are demonstrated for OSCs based on SnO_(2)/UV cross-linked resins compared to OSCs utilizing bare SnO_(2).We believe that UV cross-linking oligomers will play a key role as interfacial modifiers in the future fabrication of large-area and flexible OSCs with high efficiency and stability.

Polymer donors with hydrophilic side-chains enabling efficient and thermally-stable polymer solar cells by non-halogenated solvent processing

Polymer solar cells(PSCs)with high power conversion efficiency(PCE)and environment-friendly fabrication are the main requirements enabling their production in industrial scale.While the use of non-halogenated solvent processing is inevitable for the PSC fabrication,it significantly reduces the processability of polymer donors(PDS)and small-molecule acceptors(SMAs).This often results in unoptimized blend morphology and limits the device performance.To address this issue,hydrophilic oligoethylene glycol(OEG)side-chains are introduced into a PD(2EG)to enhance the molecular compatibility between the PD and L8-BO SMA.The 2EG PD induces higher crystallinity and alleviates phase separation with the SMA compared to the reference PD(PM7)with hydrocarbon side-chains.Consequently,the 2EG-based PSCs exhibit a higher PCE(15.8%)than the PM7-based PSCs(PCE=14.4%)in the ortho-xylene based processing.Importantly,benefitted from the reduced phase separation and increased crystallinity of 2EG PDS,the 2EG-based PSCs show enhanced thermal stability(84%of initial PCE after 120 h heating)compared to that of the PM7-based PSCs(60%of initial PCE after 120 h heating).This study demonstrates the potential of OEG side-chain-incorporated materials in developing efficient,stable,and eco-friendly PSCs.

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.

Low temperature,non-halogen solvent processed single-component organic solar cells with 10%efficiency

A double-cable conjugated polymer DCPIC-BO is designed via introducing a long-branched alkyl chains 2-buthyloctyl into the acceptor side unit.Compared with the double-cable polymer(DCPIC-EH)with the 2-ethylhexyl alkyl chains,the solubility of the DCPIC-BO in non-halogen solvents is substantially improved.Therefore,a power conversion efficiency(PCE)of 9.77%can be obtained by the devices processed from o-xylene at 40℃,while the DCPIC-EH cannot be processed due to its poor solubility under this condition.Moreover,PCEs of 10.10%for small-area(0.04 cm^(2))devices and nearly 9%for devices with an area of 1 cm^(2) are achieved using a non-halogenated solid additive in o-xylene,realizing the"absolutely halogen-free"OSC fabrication.

High-efficiency single and tandem fullerene solar cells with asymmetric monofluorinated diketopyrrolopyrrole-based polymer

Design and synthesis of low bandgap(LBG) polymer donors is inevitably challenging and their processability from a non-halogenated solvent system remains a hurdle to overcome in the area of highperformance polymer solar cells(PSCs).Due to a high aggregation tendency of LBG polymers,especially diketopyrrolopyrrole(DPP)-based polymers coupled with bithiophenes in the polymer backbones,their widespread adoption in non-ha logena ted solvent-processed PSCs has been limited.Herein,a novel LBG DPP-based polymer,called PDPP4 T-1 F with asymmetric arrangement of fluorine atom,has been successfully synthesized and showed an outstanding power conversion efficiency(PCE) of 10.10% in a singlejunction fullerene-based PSCs.Furthermore,an impressive PCE of 13.21% has been achieved in a tandem device from a fully non-halogenated solvent system,which integrates a wide bandgap PDTBTBz-2 F polymer in the bottom cell and LBG PDPP4 T-1 F polymer in the top cell.The achieved efficiency is the highest value reported in the literature to date in fullerene-based tandem PSCs.We found that a uniformly distributed interpenetrating fibril network with nano-scale phase separation and anisotropy of the polymer backbone orientation for efficient charge transfer/transport and suppressed charge recombination in PDPP4 T-1 F-based PSCs led to outstanding PCEs in single and tandem-junction PSCs.

Polythiophene solar cells processed from non-halogenated solvent with 15.68%efficiency

Polythiophenes(PTs)are prospective polymer donors for large-scale manufacturing and industrialization owing to their simple structures and low synthetic cost.However,the fabrication of PT solar cells depends on highly toxic chlorinated solvents,and less research has been done on the use of more environmentally friendly non-halogenated solvents.Herein,highly efficient PT solar cells based on top-performance polythiophene,P5TCN-F25,processed from a non-halogenated solvent are reported by delicate aggregation control.A power conversion efficiency of up to 15.68%was achieved by depositing the active layer from a hot o-xylene solution,which is the record efficiency of non-halogenated processed PT solar cells up to date.The appropriate solution temperature is beneficial to the formation of ordered polymer stacking and desirable phase separation size,which thereby contributes to enhanced charge transfer efficiency,more balanced hole/electron mobility,and reduced trap-assisted recombination.These results provide valuable implications for improving the efficiency of PT solar cells via environmentallyfriendly processing.

The development of A-DA’D-A type nonfullerene acceptors containing non-halogenated end groups

Compared with perovskite solar cells and silicon solar cells,the excessive voltage loss(Vloss)becomes a stubborn stone that seriously hinders the further improvement of organic photovoltaic(OPV).Thus,many researchers focus on finding an effective material system to achieve high-performance OPVs with low Vloss.In recent 5 years,acceptor-donor-acceptor’-donor-acceptor(A-DA’D-A)type non-fullerene acceptors(NFAs)have attracted great attention because of their promising photovoltaic performance.Among them,A-DA’D-A type NFAs containing non-halogenated end group(NHEG)exhibit the large potential to achieve high open-circuit voltage(VOC)for the state-of-the-art OPVs,because of high-lying molecular energy levels and decreasing Vloss.In this review,we systematically summarize the recent development of A-DA’D-A type NHEG-NFAs and the impact of different NHEGs on the optoelectronic properties as well as the photovoltaic performance.In addition,we especially analyze the Vloss of NHEG-NFAs in the binary and ternary OPV devices.At last,we provide perspectives on the further molecular design and future challenges for this kind of materials as well as suggested solutions.

Development of Non-Halogen Flame Retardant Optical Fiber and Optical Fiber Cord

A non-halogen highly flame-retardant 0.9mm optical fiber and 2.0mm simplex optical cord, which are harmonized with the ecosystem, have been developed. The characteristics of them are presented in this paper.

High-efficiency organic solar cells processed from a halogen-free solvent system

The use of non-halogenated solvents for the green manufacture of high-efficiency organic solar cells(OSCs)is important for their future application.However,the power conversion efficiency(PCE)of the non-halogenated solvent processed OSCs is generally lower than their halogenated counterpart due to the poor film microstructure caused by the solubility issue.Herein,we propose a halogen-free solvent system to optimize film microstructure of the photovoltaic blend based on the polymer donor D18and small-molecule acceptor(SMA)L8-BO towards high-efficiency OSCs.The solvent system is consisted of a main solvent carbon disulfide and an additive paraxylene,where the former ensures the good solution-processability and promotes the solution aggregation of L8-BO,and the latter can finely control the phase-separation process by selectively dissolving the SMA.This solvent combination robustly produces a high-quality active layer,i.e.,the bicontinuous networks of donor and acceptor with nano-sized phase-separation and strongπ-πstacking.With the effective charge generation,transport and collection,the resulting device from the non-halogenated solvent system shows a high PCE of 17.50%,which is comparable to that of the device prepared from the halogenated solvent chloroform(ca.17.11%).This article proposes a new strategy for the green fabrication of high-efficiency OSCs to accelerate their industrialization.

Slot-die coated large-area flexible all-polymer solar cells by nonhalogenated solvent

The slot-die coating is recognized as the most compatible method for the roll-to-roll(R2R)processing of large-area flexible organic solar cells(OSCs).However,the photovoltaic performance of the large-area flexible all-polymer solar cells was significantly lagging behind that of polymer donors with small molecule non-fullerene acceptors devices.In this work,the 1 cm^(2) flexible device of an all-polymer system,PTQ10:PYF-T-o,fabricated by slot-die coating,achieves an excellent efficiency of 11.24%via controlling the coating temperatures.It is found that,compared with the donor,the crystallinity of PYF-T-o plays a crucial role in device performance.The all-polymer flexible devices show superior mechanical bending stability,maintaining an efficiency of over 95%of the initial value during a 1000-cycle bending test.

Low-cost organic photovoltaic materials with great application potentials enabled by developing isomerized non-fused ring acceptors

Benefitting from low cost and simple synthesis,simple structured non-fused ring acceptors(NFRAs)and polymer donors are crucial for the application of organic solar cells(OSCs).Herein,two isomerized NFRAs,namely 4T-FCl FCl and 4T-2F2Cl,are designed with end-group engineering,which modulates the electrostatic potential distributions and crystallinity of acceptors,and accordingly,the A/A and D/A intermolecular interactions.The OSC based on 4T-2F2Cl with strong D/A interactions shows a record-high efficiency of 16.31%in blending with a low-cost polymer donor PTQ10,which shapes obviously improved bulkheterojunction(BHJ)networks blade-coated by non-halogenated solvent o-xylene,and thus significantly diminishes nonradiative recombination loss.A higher industrial figure of merit(i-FOM)of 0.46 for PTQ10:4T-2F2Cl in comparison with PTQ10:4T-FCl FCl(i-FOM=0.29)is demonstrated owing to its superior device efficiency and operational stability.Note that the i-FOM of PTQ10:4T-2F2Cl is the highest value for OSCs reported so far.This work deepens the synergistic effect of the A/A and D/A interactions on achieving desired bulk heterojunction morphology and demonstrates a printable photovoltaic system for low-cost,high-efficiency,stable,and eco-friendly OSCs.