骨架非稠合的电子受体在聚合物太阳能电池中的应用

Non-fullerene electron acceptors have attracted enormous attention of the research community owing to their advantages of optoelectronic and chemical tunabilities for promoting high-performance polymer solar cells (PSCs). Among them, fused-ring electron acceptors (FREAs) are the most popular ones with the good structural planarity and rigidity, which successfully boost the power conversion efficiencies (PCEs) of PSCs to over 14%. In considering the cost-control of future scale-up applications, it is also worthwhile to explore novel structures that are easy to synthesize and still maintain the advantages of FREAs. In this work, we design and synthesize a new electron acceptor with an unfused backbone, 5, 5'-((2, 5-bis((2-hexyldecyl)oxy)-1, 4-phenylene)bis(thiophene-2-yl))bis(methanylylidene)) bis(3-oxo-2, 3-dihydro-1H-indene-2, 1-diylidene))dimal-ononitrile (ICTP), which contains two thiophenes and one alkoxy benzene as the core and 2-(3-oxo-2, 3-dihydroinden-1-ylidene) malononitrile (IC) as the terminal groups. The synthetic route to ICTP involves only three steps, with high yields. Density functional theory calculations indicate that the non-covalent interactions, O…H and O…S, help reinforce the space conformation between the central core and the terminals. ICTP shows broad and strong absorption in the long-wavelength range between 500 and 760 nm. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels of ICTP were measured to be -5.56 and -3.84 eV by cyclic voltammetry. The suitable absorption and energy levels make ICTP a good acceptor candidate for medium bandgap polymer donors. The best devices based on PBDB-T:ICTP showed a PCE of 4.43%, with an open circuit voltage (V_OC) of 0.97 V, a short circuit current density (J_SC) of 8.29 mA∙cm^-2, and a fill factor (FF) of 0.55, after adding 1% 1, 8-diiodooctane (DIO) as the solvent additive. Atomic force microscopy revealed that DIO could ameliorate the strong aggregation in the blended film and lead to a smoother film surface. The hole and electron mobilities of the optimized device were measured to be 9.64 and 2.03 × 10^-5 cm²∙V^-1∙s^-1, respectively, by the space-charge-limited current method. The relatively low mobilities might be responsible for the moderate PCE. Further studies can be performed to enlarge the conjugation length by including more aromatic rings. This study provides a simple strategy to design non-fullerene acceptors and a valuable reference for the future development of PSCs.     

Synthesis and Absorption Spectra of n‐Type Conjugated Polymers Based on Perylene Diimide

Two novel n‐type conjugated polymers based on perylene diimide (PDI), poly(PDI‐vinylene) (PDIV), and poly(PDI‐thienylene) (PDITh), have been designed and synthesized by the Stille coupling reaction. In comparison with the PDI monomer (compound M1), PDIV and PDITh films show a significantly broad absorption band from 380 to 720 nm, and a narrower bandgap of ≈1.71 and 1.74 eV, respectively. Cyclic voltammograms of the two polymers display a couple of reversible reduction/re‐oxidation (n‐doping/dedoping) peaks. The onset reduction (n‐doping) potentials of PDIV and PDITh are at −0.62 V and −0.66 V versus Ag/Ag⁺ respectively, which correspond to the electron affinities (EAs) of 4.09 eV for PDIV and 4.05 eV for PDITh. The EA values of the two polymers are the highest among the n‐type conjugated polymers reported to date. The results indicate that PDIV and PDITh could be used as polymer acceptors in all polymer solar cells.

     

A new perspective for organic solar cells: triplet nonfullerene acceptors

正In the last decade,the rapid development of bulk heterojunction(BHJ)organic solar cells(OSCs)has been witnessed and the power conversion efficiencies(PCEs)have reached over 13%[1].Though fullerene derivatives have played dominant roles for BHJ OSCs,nonfullerene acceptors recently showed a promising potential in replacing fullerene derivatives since they possess readily tunable bandgaps,strong and broad absorption,and low cost production[2,3].     

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.     

Synthesis and properties of novel sulfonated polyimides containing phthalazinone moieties for PEMFC

A novel sulfonated diamine, 1,2-dihydro-2-(3-sulfonic-4-aminophenyl)-4-[4-(3-sulfonic-4-aminophenoxy)-phenyl]-phthalazin-1-one(S-DHPZDA), was successfully synthesized and two series of six-membered sulfonated polyimides (SPIs) were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), S-DHPZDA, and nonsulfonated diamines DHPZDA or 4,4′-diaminodiphenyl ether (ODA). The chemical structure of the S-DHPZDA and the SPIs were characterized by ¹H NMR and FT-IR. Tough, brownish and transparent membranes were cast from SPIs’ solution in NMP. The water uptake, swelling ratio, chemical and thermal stability, hydrolytic and oxidative stability as well as proton conductivity of these new polymers were investigated systematically. Compared with Nafions, the obtained SPI membranes have onset decomposed temperatures of these two series SPIs were above 318 °C and decomposed temperature of main chain were 565 °C and excellent dimension stabilities on similar IECs. Introduction of phthalazinone moieties had improved the copolyimides’ solubility in polar aprotic organic solvents like m-cresol, NMP, DMSO, DMF etc. The SPIs had high proton conductivity (σ) in the order of magnitude of 10⁻³ to 10⁻² S cm⁻¹ depending on the degree of sulfonation (DS) of the polymers.     

PMMA colloid particles stabilized by layered silicate with PMMA-b-PDMAEMA block copolymer brushes

The amphiphilic poly(methyl methacrylate-block-2-(dimethylamino)ethyl methacrylate) (PMMA-b-PDMAEMA) block copolymer brushes on the surface of clay layers were synthesized by in situ atom transfer radical polymerization. X-ray diffraction results indicate that both exfoliated and intercalated structure can be found in the nanocomposites. The block copolymer brushes can make different nanopatterns on the surface of clay layers after treatment in different solvents. After treatment in tetrahydrofuran block copolymer brushes form lamella structure on the surface, and after treatment in water surface micelles and wormlike structure can be observed. PMMA colloid particles armored by clay nanocomposites were prepared by suspension polymerization. Transmission electron microscopy and scanning electron microscopy were used to characterize the structure and morphology of the colloid particles. Colloid particles with clay layers around the surface can be observed. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface of the colloid particles. N1s binding energy of PDMAEMA blocks on the surface of clay layers was detected by XPS. The two peaks of the N1s binding energy indicate two different nitrogen environments on the surface of clay layers. The peak with a lower binding energy is characteristic of neutral nitrogen on PDMAEMA blocks, and the peak with a higher binding energy is attributed to protonated nitrogen on PDMAEMA blocks.     

苯并10芳杂环化合物的合成

近年来符合休克尔规则的,经典的6π芳香环以外的大环或多环芳香族化合物的合成及其应用的开发曰益受到人们的重视^[1,2]。本文简要介绍含有三氟甲基及三氟乙酰基的苯并10π-芳杂环化合物的合成及其结构的确定。此类化合物目前文献中尚未见报导。     

Breaking 12% efficiency in flexible organic solar cells by using a composite electrode

The performance of flexible organic solar cells(OSCs)significantly relies on the quality of transparent flexible electrode.Here,we used silver nanowires(AgNWs)with various weight ratios to dope high-conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate(PH1000)to optimize the optical and electronic properties of PH1000 film.A high-quality flexible composite electrode PET/Ag-mesh/PH1000:AgNWs-20 with smooth surface,a low sheet resistance of 6Ω/sq and a high transmittance of 86%at 550-nm wavelength was obtained by doping 20 wt%AgNWs to PH1000(PH1000:AgNWs-20).The flexible OSCs based on the PET/Ag-mesh/PH1000:AgNWs-20 electrode delivered a power conversion efficiency(PCE)of12.07%with an open circuit voltage(V_(oc))of 0.826 V,a short-circuit current density(J_(sc))of 20.90 m A/cm~2and a fill factor(FF)of69.87%,which is the highest reported PCE for the flexible indium-tin oxide(ITO)-free OSCs.This work demonstrated that the flexible composite electrodes of PET/Ag-mesh/PH1000:AgNWs are promising alternatives for the conventional PET/ITO electrode,and open a new avenue for developing high-performance flexible transparent electrode for optoelectronic devices.     

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 V_(oc)of 0.96 V,a superior J_(sc)of 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 N_2-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.