Low-bandgap polymers with quinoid unit as π bridge for high-performance solar cells

To construct efficient low band gap polymers,increasing the Quinone structure of the polymer backbone could be one desirable strategy.In this work,two D–Q–A–Q polymers P1 and P2 were designed and synthesized with thiophenopyrrole diketone(TPD)and benzothiadiazole(BT)unit as the core and ester linked thieno[3,4-b]thiophene(TT)segment as π-bridging,and the main focus is to make a comparative analysis of different cores in the influence of the optical,electrochemical,photochemical and morphological properties.Compared with the reported PBDTTEH–TBTTHD-i,P1 exhibited the decreased HOMO energy level of-5.38 e V and lower bandgap of 1.48 e V.Furthermore,when replaced with BT core,P2 showed a red-shifted absorption profile of polymer but with up-shifted HOMO energy level.When fabricated the photovoltaic devices in conventional structure,just as expected,the introduction of ester substituent made an obvious increase of VOC from 0.63 to 0.74 V for P1.Besides,due to the deep HOMO energy level,higher hole mobility and excellent phase separation with PC71 BM,a superior photovoltaic performance(PCE=7.13%)was obtained with a short-circuit current density(JSC)of 14.9 m A/cm^2,significantly higher than that of P2(PCE=2.23%).Generally,this study highlights that the strategy of inserting quinoid moieties into D–A polymers could be optional in LBG-polymers design and presents the importance and comparison of potentially competent core groups.

Efcient soluble PTCBI‑type non‑fullerene acceptor materials for organic solar cells

Single perylene diimide(PDI)used as a non-fullerene acceptor(NFA)in organic solar cells(OSCs)is enticing because of its low cost and excellent stability.To improve the photovoltaic performance,it is vital to narrow the bandgap and regulate the stacking behavior.To address this challenge,we synthesize soluble perylenetetracarboxylic bisbenzimidazole(PTCBI)molecules with a bulky side chain at the bay region,by replacing the widely used“swallow tail”type alkyl chains at the imide position of PDI molecules with a planar benzimidazole structure.Compared with PDI molecules,PTCBI molecules exhibit red-shifted UV–vis absorption spectra with larger extinction coefcient,and one magnitude higher electron mobility.Finally,OSCs based on one soluble PTCBI-type NFA,namely MAS-7,exhibit a champion power conversion efciency(PCE)of 4.34%,which is signifcantly higher than that of the corresponding PDI-based OSCs and is the highest PCE of PTCBI-based OSCs reported.These results highlight the potential of soluble PTCBI derivatives as NFAs in OSCs.

A Randomized Controlled Trial of a Biodegradable Polymer,Microcrystalline Sirolimus-Eluting Stent(MiStent)versus Another Biodegradable Polymer Sirolimus-Eluting Stent(TIVOLI):The DESSOLVE-C Trial

Objective::Data comparing the outcomes of MiStent(Micell Technologies,Durham,North Carolina,USA)microcrystalline biodegradable polymer(BP)drug-eluting stent(DES)and those of another post-marketing BP-DES,TIVOLI(EssenTech,Beijing,China)are rare.This study sought to compare the angiographic efficacy and clinical outcomes of the microcrystalline BP sirolimus-eluting stent(SES)system MiStent and those of TIVOLI BP-SES.Methods::The DESSOLVE-C trial was a prospective,single-blinded,multicenter,randomized trial(NCT02448524),which randomly assigned patients with de novo coronary lesions to receive MiStent or TIVOLI BP-SES by a 1:1 ratio.The primary endpoint was a non-inferiority comparison of in-stent late lumen loss(LLL)by quantitative coronary angiography at 9 months.The secondary endpoint was device-related clinical cardiovascular composite events(target lesion failure(TLF),composite of cardiac death,target vessel myocardial infarction(MI),and clinically driven target lesion revascularization)and 1-year outcomes.Results::A total of 428 patients(216 patients in the MiStent group and 212 patients in the TIVOLI group)were enrolled and included in an intention-to-treat analysis.MiStent was not only non-inferior but superior to TIVOLI for in-stent LLL at 9 months((0.23±0.37)mm vs.(0.34±0.48)mm,P for non-inferiority<0.001,P for superiority=0.02).Although without significant difference,the rate of TLF in MiStent was quantitatively lower than that in TIVOLI(3.70%vs.6.60%;P=0.17).Conclusion::Compared with TIVOLI BP-SES,the MiStent system was superior in in-stent LLL at 9 months and had a comparable clinical benefit at 1 year in de novo coronary lesions.

High open-circuit voltage solution-processed organic solar cells based on a star-shaped small molecule end-capped with a new rhodanine derivative

A new star-shaped small molecule named TCNR3TTPA,with a triphenylamine(TPA)unit as the central building block and2-(1,1-dicyanomethylene)-3-octyl rhodanine(CNR)as the end-capped group,has been designed and synthesized.TCNR3TTPA showed a deep highest occupied molecular orbital(HOMO)energy level( 5.60 e V)and broad absorption.The solution-processed bulk heterojunction(BHJ)solar cells based on TCNR3TTPA:PC61BM(1:1,w/w)exhibited a high open-circuit voltage(Voc)of 0.99 V,a short-circuit current density(Jsc)of 5.76 m A/cm2,and a power conversion efficiency(PCE)of 2.50%under the illumination of AM 1.5 G,100 m W/cm2.The high Voc is ascribed to the strong electron-with-drawing ability of the end-capped 2-(1,1-dicyanomethylene)-3-octyl rhodanine group.These results demonstrated that the Voc of small-molecule organic solar cells could be increased by introducing a strong electron-withdrawing end-capped block,and that this is an effective strategy to design high-performance small molecules for organic solar cells.

Subtle Side Chain Triggers Unexpected Two-Channel Charge Transport Property Enabling 80%Fill Factors and Efficient Thick-Film Organic Photovoltaics

To clearly show how important the impact of side chains on organic solar cells(OSCs)is,we designed three acceptors IDIC-CxPh(x=4,5,or 6)via subtle side-chain regulation.Despite this small change,significant distinctions were detected.IDIC-C4Ph devices achieve an optimal efficiency of 13.94%under thermal annealing,but thermal-assistant solvent-vapor annealing hugely suppresses the efficiencies to 10%.However,the C6Ph side chain endows extremely disordered stacking orientations,generating moderate efficiencies of~12.50%.Excitingly,the IDIC-C5Ph affords an unexpected two-channel p-p charge transport(TCCT)property,boosting the fill factor(FF)by up to 80.02%and efficiency to 14.56%,ranking the best among five-ring fused-ladder-type acceptors.Impressively,the special TCCT behavior of IDIC-C5Ph enables 470 nm thick-film OSC with a high FF of up to 70.12%and efficiency of 13.01%,demonstrating the great promise in fabricating largescale OSCs.