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In this work, we designed and synthesized two small molecular acceptors, based on benzotriazole (BTA) as the center core with isopropyl alkyl chain, thienothiophene unit (TT) β-position connected n-hexane alkyl chain as wing, and using different end groups, 2-(3-oxygen generation-2, 3-2H − 1H-indane-1-alkyl)-malononitrile (IC) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-indane-1-alkylene) (2FIC), named BIT-IC and BIT-2FIC, respectively. The device based on PM6: BIT-IC achieved the PCE of 3.63%, which exhibited inferior performance because the device absorption is not complementary with solar spectrum, leading to the low Jsc of the device. However, the absorption band of the acceptor BIT-2FIC with 2FIC end group can reach 944 nm, and the HOMO energy level is lower than BIT-IC, therefore, the device based on PM6: BIT-2FIC can achieve more efficient exciton dissociation and charge transport, after thermal annealing treatment at 90 °C for 10 min, the device based on PM6: BIT-2FIC can achieve the PCE over 14%.

Semitransparent organic solar cells (ST-OSCs) have drawn great attention due to their wide application, such as smart windows, greenhouses and building integrated photovoltaics. The ternary strategy is often considered an useful way to enhance device performance due to improve the attracting or retracting morphology. Here, non-fullerene small molecule (Y8) with electron-deficient core as the center unit and a novel PBDTTT-type low-bandgap polymer (PCE10) were chosen to fabricate ST-OSCs according to the principle of more closely matched energy levels. With the introduction of indene-C60bisadduct (ICBA) as third component, opaque organic solar cells with a power conversion efficiency (PCE) of 12.86% and ST-OSCs with a PCE of 10.46% were obtained by using spin coating after optimization. The average visible transmittance of ST-OSCs is up to 26.56%. By the blade coating technique, 9.52% PCE is achieved for ST-OSCs, which is the highest value reported to date. These results show that it's higher efficiency to improve the performance of ST-OSCs through ternary strategy. And the blade coating technique has a promising application prospect for mass manufacturing ST-OSCs.

Considering serious concrete diseases from tunnel lining structure, the pre-suspended nanomaterials combined with superfine admixtures (nano-SA) are used to improve mechanical properties and durability of concrete. Fly ash combined with ultrafine particle microspheres were selected as composite admixtures based on comprehensive performance and application research analysis on the mineral nanomaterial admixtures. Compressive strength and flexural strength for the mortar specimens at different ages were investigated by the single or composite incorporation of the silica fume and the other nanomaterials with the different physical properties. The nano-SA determined by experiment was applied to regulate strength and durability of the concrete. The Scanning Electron Microscopy (SEM) was used to analyze microstructure of concrete with different prescriptions under freeze–thaw cycles. The effects of the nano-SA acting on concrete compactness were studied. The pre-suspended nanomaterial combined with superfine admixture is used for the experimental shotcrete of tunnel. The experimental results indicate that the nano-SA not only improves the workability and compressive strength of the shotcrete but also significantly reduces the rebound rate of the shotcrete. The rebound amount of the shotcrete incorporated with the nano-SA is decreased approximately 30% than without the nano-SA. It proves the excellent performance of the nano-SA and obvious economic benefits.

In comparison with symmetric small molecule acceptors (SMAs), their asymmetric counterparts have received much less attention. Organic solar cells (OSCs) based on asymmetric non-fullerene SMAs previously reported show relatively low power conversion efficiency (PCE < 15%) and lower short circuit current densities (Jsc < 20 mA cm−2), although they exhibit a larger dipole moment and stronger intermolecular interactions. Here we report a new asymmetric A–D1A′D2–A type SMA, namely Y22, containing an asymmetric hexacyclic fused donor–acceptor–donor (DA′D) type central framework and end-capped with two electron-deficient 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile moieties. Y22 shows good solubility and a broad near-infrared absorption. The effects of the asymmetric structure on the physicochemical and photovoltaic performance were systematically investigated. Y22-based OSCs were fabricated by using PM6, QX2 and J71 as polymer donors, all exhibiting high PCEs over 10%. Notably, the optimal PM6:Y22-based device shows a high PCE of 15.4% and a high Jsc of 24.37 mA cm−2, which is among the best values reported for asymmetric SMA based OSCs, attributed to the fine nanofiber morphology after thermal annealing and solvent addition. This work demonstrates that the asymmetric fused structure with an electron-deficient-core is a promising building block to build high performance SMAs towards efficient photovoltaic applications.

In this work, two non-fullerene small molecule acceptors (NFSMAs), named IFIC and IFIC-F, were designed and synthesized by introducing alkoxy-phenyl as the side chain and furan as π-bridge. This method enhances the intermolecular charge transfer between HFQx-T and IFIC-F (IFIC). Besides, IFIC and IFIC-F exhibit strong and broad absorption ranging from 550 nm to 800 nm. IFIC-F with alkoxy-phenyl exhibits an absorption peak at 702 nm, which has a redshift of 17 nm compared with IFIC (685 nm). The power conversion efficiency (PCE) of organic solar cell based on HFQx-T: IFIC is 6.28%, which is higher than the PCE of device based on HFQx-T: IFIC-F (5.87%). These results indicate that inserting alkoxy–phenyl side chain and furan π-bridge are a rational strategy for the synthesis of high-performance NFSMAs.

Here, we report a facile molecular engineering approach with alkylthio and fluorine atom modified the conjugated side chain of quinoxaline-based polymer, namely DTFFQx-TS, which afforded lower highest occupied molecular orbital energy level and enhanced interchain interactions. The conventional devices based on DTFFQx-TS:ITIC exhibited the power conversion efficiency (PCE) of 5.26% with a remarkably high open circuit voltage (Voc) of 0.99 V. This work not only provides a newly efficient candidate of quinoxaline acceptor block modified with fluorinated conjugated side chain, but also achieves high Voc copolymers for polymer solar cells via the synergistic effect of fluorination and side chain engineering strategies.

Summary Recently, non-fullerene n-type organic semiconductors have attracted significant attention as acceptors in organic photovoltaics (OPVs) due to their great potential to realize high-power conversion efficiencies. The rational design of the central fused ring unit of these acceptor molecules is crucial to maximize device performance. Here, we report a new class of non-fullerene acceptor, Y6, that employs a ladder-type electron-deficient-core-based central fused ring (dithienothiophen[3.2-b]- pyrrolobenzothiadiazole) with a benzothiadiazole (BT) core to fine-tune its absorption and electron affinity. OPVs made from Y6 in conventional and inverted architectures each exhibited a high efficiency of 15.7%, measured in two separate labs. Inverted device structures were certified at Enli Tech Laboratory demonstrated an efficiency of 14.9%. We further observed that the Y6-based devices maintain a high efficiency of 13.6% with an active layer thickness of 300 nm. The electron-deficient-core-based fused ring reported in this work opens a new door in the molecular design of high-performance acceptors for OPVs.

In the paper, the quinoxaline(QX) polymer donor material with 4-methoxythiophene as the side chain was designed and synthesized by side chain modification engineering and named as PBMOQX. It has good solubility in common organic solvents. In addition, a series of characterizations of the conjugated polymer were performed. There is a good spectral absorption at 300–700 nm with an electrochemical bandgap of 1.83 eV and an optical bandgap of 1.63 eV. With 0.5% of 1, 8-diiodooctane as an additive in a mixing ratio of PBMOQX: PC71BM = 1:1.5, the device achieves a power conversion efficiencies (PCE) of 6.94%. These studies indicate that the novel copolymer PBMOQX is a promising photovoltaic donor material for high efficiency polymer solar cells (PSCs).

Rational molecular design of n-type organic semiconductors with strong near-infrared absorption and visible-light transmittance is critical but still a challenge for application in high efficiency semitransparent organic solar cells (OSCs). Here, by employing fluorinated 2-(2,3-dihydro-3-oxo-1H-inden-1-ylidene)propanedinitrile as an end group, a fused dithienothiophen[3,2-b]-pyrrolobenzotriazole (BTA-core)-based low bandgap electron acceptor, namely Y14, has been designed and synthesized to address this issue. The BTA-core-based non-fullerene acceptor has relatively high electron mobility and a broad absorption from 300 to 1000 nm. The Y14-based single-junction opaque and semitransparent inverted OSCs achieved high power conversion efficiencies (PCEs) of 14.92% and over 12%, respectively. By further optimizing the semitransparent device with additive treatment and thermal annealing, a higher PCE of 12.67% was realized with an average visible transmittance (AVT) of 23.69%. These results demonstrate that this BTA-core-based structure toward non-fullerene acceptors is a universal strategy that is not only suitable for high efficiency OSCs, but also has great potential as an acceptor material in semitransparent devices.

In the paper, a new A–π-D–π-A small molecule with alkoxyphenyl substituted naphtho[1,2-b:5,6-b′]difuran (NDFP) as the central building block, named as NDFP-CNCOO which was synthesized and firstly used as donor materials in organic solar cells (OSCs). After thermal annealing (TA), the blend of NDFP-CNCOO /PC71BM (1:1, w/w) exhibited a high electron mobility of 1.84 × 10−4 cm2 V−1 s−1. Using a structure of ITO/PEDOT:PSS/NDFP-CNCOO: PC71BM/Al, the device delivered a moderate power conversion efficiency (PCE) of 4.60% and a high fill factor (FF) of 57% with TA at 110 °C. The investigations show that NDFP-CNCOO could be a promising building block in OSCs via rational molecular structure design and device optimizations.

Development of high-performance donor–acceptor (D–A) copolymers has been indicated as a promising strategy to improve the power conversion efficiencies (PCEs) of organic solar cells (OSCs). In this work, a new medium bandgap conjugated D–A copolymer, HFAQx-T, based on 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDT-T) as donor unit, 4-alkyl-3,5-difluorophenyl substituted quinoxaline (HFAQx) as the acceptor unit, and thiophene as the spacer, was designed and synthesized. HFAQx-T is a well-compatible donor polymer; OSCs based on HFAQx-T exhibit excellent performance in both fullerene and fullerene-free based devices. The optimized conventional single junction bulk heterojunction (BHJ) OSCs of HFAQx-T:PC71BM showed a PCE of 9.2%, with an open circut voltage (Voc) of 0.9 V, a short circuit current (Jsc) of 14.0 mA cm–2, and a fill factor (FF) of 0.74. Also, when blended with 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone)-5,5,11,11-tetrakis(4-hexylphenyl)dithieno[2,3-d:2′,3′-d...

In this paper, the effect of Na substitution for La on Li ion conductivity in the well-known Li5La3Nb2O12 parents with the cubic garnet framework prepared by sol-gel process is reported. The optimum condition is at 750 °C for 6 h in air with 10% excess lithium salt. The power XRD patterns reveal that the partial substitutions of Na for La in Li5 + 2xLa3-xNaxNb2O12 electrolytes are isostructural. The cubic lattice parameters decrease as the molar fractions of Na increasing. Among the Li5 + 2xLa3-xNaxNb2O12 compounds investigated, the Na-substituted Li6.4La2.3Na0.7Nb2O12 exhibits the highest ionic conductivity of 1.6 × 10−4 S cm-1 at room temperature with an activation energy of 0.41 eV. The new solid state electrolyte is very stable in potential range of −0.8 to 5.0 V vs. Li/Li+, and is also chemically stable against LiMn2O4 and LiCoO2 compounds up to 900 °C, indicating that Li6.4La2.3Na0.7Nb2O12 is a promising solid state electrolyte for all-solid-state battery application.

Two medium bandgap polymers (ffQx-TS1, ffQx-TS2) were designed and synthesized to investigate the influence of different alkylthio side chain on the morphology and photovoltaic performance of non-fullerene polymer solar cells (PSCs). Both polymers exhibit similar molecular weights and comparable the highest occupied molecular orbital (HOMO) energy level. However, the polymer with straight alkylthio chain delivers a root-mean-square (RMS) of 0.86 nm, which is slightly lower than that with branched chain (1.40 nm). The lower RMS benefits the ohmic contact between the active lay and interface layer, thus enhanced short circuit current (Jsc) (from 13.54 mA cm−1 to 15.25 mA cm−1) could be obtained. Due to the enhancement of Jsc, better power conversion efficiency (PCE) of 7.69% for ffQx-TS2 could be realized. These results indicated that alkylthio side chain engineering is a promising method to improve photovoltaic performance.

Quinoxaline (Qx) has an easily modifiable structure, which allows for fine-tuning its properties through optimizing the length of side chains and the kinds of aromatic rings in conjugated side chains. Qx based polymer PBDTT-ffQx with alkoxy substituted fluorobenzene side chains shows a power conversion efficiency (PCE) of 8.47% in nonfullerene solar cells. In this work, we change the alkoxy substituted fluorobenzene side chains to alkyl substituted fluorothiophene in the Qx unit and employ the benzodithiophene (BDT) unit with different lengths of alkyl thiophene side chains to obtain two new Qx based polymers, named TTFQx-T1 and TTFQx-T2, respectively. The TTFQx-T1:ITIC blend film has clear nanoscale phase separation and a suitable domain size, and the device with the TTFQx-T1:ITIC blend film shows lower geminate recombination and higher charge mobility than those with TTFQx-T2:ITIC. Therefore, the TTFQx-T1:ITIC based device exhibits a higher PCE of 10.52% than that based on the TTFQx-T2:ITIC blend with a moderate PCE of 7.22%. The inverted devices from TTFQx-T1:ITIC blends with a larger active area of 16 mm2 than the conventional device (4.5 mm2) show a good PCE of 9.21%. The results highlight that the alkyl lengths and the kinds of aromatic rings in side chains are significant for the development of high performance photovoltaic polymers. Optimizing the conjugated side chains of Qx based polymers is an efficient way to improve photovoltaic properties, and Qx based polymers are potential candidates for fabricating highly efficient polymer solar cells.

In this work, a non-fullerene acceptor molecule (ITIC-FOR) based on heptacyclic (indacenodithieno[3,2-b]thiophene) IDTT as the core with F-phenylalkoxy (FOR) as a side chain was designed and synthesized. The photovoltaic properties of the HFQx-T:ITIC-FOR based non-fullerene polymer solar cells (NF-PSCs) were explored. By device optimization, a good power conversion efficiency (PCE) of 7.33% was obtained.

Two new donor (D) - acceptor (A) copolymers, named m -O- p -F-DFQx-BDT (OFQx-T) and m -EH- p -F-DFQx-BDT (EHFQx-T), which were based on meta -octyloxy- para -fluorophenyl and meta -ethylhexyloxy- para -fluorophenyl difluoroquinoxaline as acceptor units (O-DFQx/EH-DFQx) and alkylthienyl substituted benzodithiophene (BDT) as a donor unit, were designed and synthesized. EHFQx-T had higher absorption coefficient than OFQx-T which contributed to larger short-circuit current density ( J sc ). EHFQx-T showed a lower the highest occupied molecular orbital (HOMO) which is beneficial for the voltage open-circuit ( V oc ). The polymer solar cells (PSCs) based OFQx-T:PC 71 BM and EHFQx-T:PC 71 BM blended film as active layer showed high power conversion efficiency (PCE) of 7.60% and 8.44%, respectively, with 1,8-diiodooctane (DIO) solvent additive treatment. More importantly, OFQx-T:PC 71 BM and EHFQx-T:PC 71 BM had good fill factor (FF), especially the FF of OFQx-T:PC 71 BM was over 70%. The high FF contributed to obtain high PCEs for OFQx-T and EHFQx-T. The more balanced and higher charge mobility, smaller geminate recombination and suitable nanoscale phase separation size of EHFQx-T demonstrate that changing octyl chain to ethylhexyl chain in DFQx acceptor unit is efficient to improve photovoltaic properties in fullerene solar cells.

In this paper, the effects of sintering additives B 2 O 3 on sintering temperature, microstructure and transport properties of the Li 7 La 3 Zr 2 O 12 (LLZ) ceramics prepared by solid state reaction are reported. The optimized conditions to synthesize the LLZ-xB 2 O 3 (x = 0.2–0.35)ceramics is 950 °C for 30 h with 10% excess lithium salt, which is nearly 300 °C lower than that by the conventional solid state reaction. Qualitative phase analysis by X-ray powder diffraction patterns combined with the Rietveld method reveals garnet type compounds as major phases. Lithium ion conductivity of LLZ-0.3B 2 O 3 was studied by AC impedance method. LLZ-0.3B 2 O 3 ceramics exhibits the highest total ionic conductivity of 2.5 × 10 − 4 S cm − 1 at room temperature. All solid state batteries consisting of Li/LLZ-0.3B 2 O 3 /mixture of LiMn 2 O 4 and LLZ-0.3B 2 O 3 /LiMn 2 O 4 cell exhibit the capacity of 102.6 mAh g − 1 at a current density of 5 μAcm − 2 at the first discharge, which could run for 20 cycles with capacity retention of 94%.

In this paper, the effect of Ge substitution for Nb on Li ion conductivity in the well-known Li5La3Nb2O12(LLN)parents with the cubic garnet framework prepared by using metal Ge is reported. The optimum condition is at 950 °C for 8 h with 10% excess lithium salt in air. The XPS spectra indicate that the metal Ge is completely transformed into Ge4+ after sintering for 8 h. The power XRD patterns reveal that the partial substitutions of Ge for Nb in Li5+xLa3GexNb2-xO12 electrolytes are isostructural. The ionic conductivity of Li5+xLa3GexNb2-xO12 ceramics increases as the molar fractions of Ge increasing for x ≤ 0.75. Among these compounds investigated, the Li5.75La3Ge0.75Nb1.25O12 exhibits the highest ionic conductivity of 1.2 × 10−4 S cm−1 at room temperature. The result can be regarded as relatively high values among the element substituted LLN garnets reported up to now. The new solid state electrolyte is very stable in potential range of −0.6-6.0 V vs. Li/Li+, indicating that Li5.75La3Ge0.75Nb1.25O12 is a promising solid state electrolyte for all-solid-state battery application.

Two new A–D–A small molecules with alkoxyphenyl and alkylthiophenyl-substituted naphtho[1,2-b:5,6-b′]difuran (NDF) as the central building block named NDFPO-DPP and NDFPS-DPP were synthesized and firstly used as donor materials in organic solar cells (OSCs). The effects of the alkoxyphenyl and alkylthiophenyl side chains on the NDF unit have been investigated. With a single atom variation from O to S, NDFPS-DPP exhibited lower HOMO energy levels than its counterpart NDFPO-DPP, which resulted in enhanced V oc . The device based on NDFPO-DPP with thermal annealing exhibited a better PCE of 3.10% due to the higher and more balanced hole and electron mobilities. The investigations show that NDF could be a promising building block in OSCs via rational molecular structure design and device optimizations.

Effect of the quenching method on conductivity of Li 5 La 3 Bi 2 O 12 ceramics prepared by sol-gel process was studied. In a synthesis process, lithium hydroxide, acetic bismuth, and acetic lanthanum were used as starting materials, while water was used as solvent. The temperature to synthesize the high density Li 5 La 3 Bi 2 O 12 with cubic garnet type structure is 750 °C for 8 h in air with 10% excess lithium salt. The samples were prepared by the same synthesis route with the only difference from cooling methods. The samples were characterized by XRD, SEM, 6 Li MAS NMR and ionic conductivity measurement. The XRD patterns of Li 5 La 3 Bi 2 O 12 ceramics showed that there was a single phase oxides with garnet-like structure by the furnace cooling and the quenching method. The Li 5 La 3 Bi 2 O 12 electrolyte by the furnace cooling exhibits the highest total ionic conductivity of 2.0 × 10 − 5 S cm − 1 at 22 °C, and that by the quenching method exhibits the highest conductivity of 2.0 × 10 − 4 S cm − 1 with a motional activation energy of 0.36 eV, which is an order of magnitude higher than that by the furnace cooling. The reason is that the relative density of Li 5 La 3 Bi 2 O 12 by the quenching method is higher than that by the furnace cooling. The SEM images are also shown that the density of Li 5 La 3 Bi 2 O 12 is very high by the quenching method and there exists lots of pores by the furnace cooling. And the 6 Li-MAS-NMR results indicate the Li 5 La 3 Bi 2 O 12 samples by the quenching method possess high Li ion mobility.

To further investigate non-fullerene polymer solar cells based-thieno[2,3- f ]benzofuran (TBF) polymers, we designed and synthesized two medium bandgap TBF-based polymers, namely TBF-BDD and TBF-BT, containing alkoxyphenyl substituted TBF electron-donor unit, 1,3-bis(thiophen-2-yl)-5,7-bis(2-ethylhexyl)benzo-[1,2- c :4,5- c ′]dithiophene-4,8-dione (BDD) and 4,7-di(thiophen-2-yl)-5,6-dioctyloxybenzo[ c ][1,2,5]thiadiazole (BT) electron-acceptor segment, respectively. When blended with ITIC (a n-type small molecule acceptor), two polymer:ITIC blends possess better complementary absorption than the absorption with PC 71 BM. The properties, including charge mobilities, and morphologies have been intensively investigated. The polymer solar cells based on TBF-BDD:ITIC and TBF-BT:ITIC (1:1, w/w ) exhibited promising power conversion efficiencies (PCEs) of 7.13% and 7.03%, respectively, under the illumination of AM 1.5 G, 100 mW/cm 2 , which are higher in comparison with fullerene-based devices. Up to now, these PCEs are the highest among TBF-based polymer photovoltaic devices.

Through introducing six fluorine atoms onto quinoxaline (Qx), a new electron acceptor unit-hexafluoroquinoxaline (HFQx) is first synthesized. On the basis of this unit, we synthesize a new donor–acceptor (D–A) copolymer (HFQx-T), which is composed of a benzodithiophene (BDT) derivative donor block and an HFQx accepting block. The strong electron-withdrawing properties of fluorine atoms increase significantly the open-circuit voltage (Voc) by tuning the highest occupied molecular orbital (HOMO) energy level. In addition, fluorine atoms enhance the absorption coefficient of the conjugated copolymer and change the film morphology, which implies an increase of the short-circuit current density (Jsc) and fill factor (FF). Indeed, the HFQx-T:ITIC blended film achieves an impressive power conversion efficiency (PCE) of 9.4% with large short-current density (Jsc) of 15.60 mA/cm2, high Voc of 0.92 V, and FF of 65% via two step annealing (thermal annealing (TA) and solvent vapor annealing (SVA) treatments). The exc...

Using solid state electrolyte instead of liquid electrolyte has been considered as a preferred alternative to the conventional liquid electrolyte. The safety and stability of electrolyte directly affects the lithium ion batteries. Lithium garnets Li 5 La 3 M 2 O 12 (M = Nb, Ta) in cubic phase exhibits higher ionic conductivity and good stability. How to continue to enhance the ionic conductivity of electrolyte is one of the key issues in development of solid state batteries. In this research, the synthesis and transport properties of the Li 5+x La 3 Hf x Nb 2-x O 12 (x = 0.2–1) samples with cubic garnet-structure type were reported by a solid state reaction for the first time. The optimized conditions to synthesize the Li 5+x La 3 Hf x Nb 2-x O 12 (x = 0.2–1) ceramics is 1100 °C for 30 h with 10% excess lithium salt. The lattice constants of Li 5+x La 3 Hf x Nb 2-x O 12 (x = 0.2–1) materials increase with increasing x due to the substitution of larger ionic radii Hf 4+ for the smaller Nb 5+ in the garnet structure. The Li 5+x La 3 Hf x Nb 2-x O 12 ceramics exhibits higher ionic conductivity than that of Li 5 La 3 Nb 2 O 12 electrolyte.

Recent advances in material design for organic solar cells (OSCs) are primarily focused on developing near-infrared non-fullerene acceptors, typically A-DA D-A type acceptors (where A abbreviates an electron-withdrawing moiety and D, an electron-donor moiety), to achieve high external quantum efficiency while maintaining low voltage loss. However, the charge transport is still constrained by unfavorable molecular conformations, resulting in high energetic disorder and limiting the device performance. Here, a facile design strategy is reported by introducing the "wing" (alkyl chains) at the terminal of the DA D central core of the A-DA D-A type acceptor to achieve a favorable and ordered molecular orientation and therefore facilitate charge carrier transport. Benefitting from the reduced disorder, the electron mobilities could be significantly enhanced for the "wing"-containing molecules. By carefully changing the length of alkyl chains, the mobility of acceptor has been tuned to match with that of donor, leading to a minimized charge imbalance factor and a high fill factor (FF). We further provide useful design strategies for highly efficient OSCs with high FF. Funding Agencies|National Key Research & Development Projects of China [2017YFA0206600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [21875286]; Science Fund for Distinguished Young Scholars of Hunan ProvinceNational Natural Science Foundation of ChinaNational Science Fund for Distinguished Young Scholars [2017JJ1029]; Innovation-Driven Project of Central South University [2020CX001]; Research Committee of HKBU [RC-ICRS/15-16/4A-SSK, FRG/16-17/077]

Correction for ‘A new non-fullerene acceptor based on the combination of a heptacyclic benzothiadiazole unit and a thiophene-fused end group achieving over 13% efficiency’ by Yunqiang Zhang et al., Phys. Chem. Chem. Phys., 2019, DOI: 10.1039/c9cp05015a.

A new small molecule, ITTC, bearing an indacenodithieno[3,2-b]thiophene core and a 2-(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-ylidene)malononitrile end group, was designed, synthesized and characterized as a non-fullerene electron acceptor. The ITTC possesses strong and broad light absorption, high and balanced charge mobility and a nanoscale interpenetrating morphology when blended with a recently synthesized hexafluoroquinoxaline based polymer donor-HFQx-T. HFQx-T was obtained from a Stille coupling copolymerization of a 2,6-bis(trimethyltin)-4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b′]dithiophene electron donating unit and a hexafluoroquinoxaline based electron accepting unit. The device employing HFQx-T as the donor and ITTC as the acceptor delivered a power conversion efficiency (PCE) of 8.19% without any post-treatment. After thermal annealing, an impressive PCE of 10.4% was obtained. This performance is among the highest PCEs reported for fullerene-free polymer solar cells up to date. This study demonstrates the great potential of ITTC as n-type materials for organic electronics.

A new asymmetric small molecule, named R3T-TBFO, with 4,8-bis(2-ethylhexyloxy)-substituted thieno[2,3-f]benzofuran (TBF) as central donor block, has been synthesized and used as donor material in organic solar cells (OSCs). With thermal annealing (TA) and solvent vapor annealing (SVA) treatment, the blend of R3T-TBFO/PC71BM shows a higher hole mobility of 1.37 × 10−4 cm2 V−1 s−1 and a more balanced charge mobilities. Using a structure of ITO/PEDOT:PSS/R3T-TBFO:PC71BM/ZrAcac/Al, the device with TA treatment delivered a moderate power conversion efficiency (PCE) of 5.63%, while device after TA + SVA treatment showed a preferable PCE of 6.32% with a high fill factor (FF) of 0.72.

Mg-doped composite, Li 2.97 Mg 0.03 VO 4, with an orthorhombic structure was prepared by a sol-gel method. The effects of the Mg doping on the structure and electrochemical performance of Li 3 VO 4 were investigated. The X-ray diffraction pattern shows that the Mg doping does not change the crystal structure of Li 3 VO 4 . The EDS mappings indicated the fairly uniform distribution of Mg throughout the grains of Li 2.97 Mg 0.03 VO 4. Electronic conductivity of Mg-doped Li 3 VO 4 increased by two orders of magnitude compared to that of pure Li 3 VO 4 . CV and EIS measurement confirms that the Li 2.97 Mg 0.03 VO 4 sample exhibits a smaller polarization and transfer resistance and a higher lithium diffusion coefficient compared with the pure Li 3 VO 4 . Due to the better electrochemical kinetics properties, Mg-doped Li 3 VO 4 showed a significant improved performance compared to the pure Li 3 VO 4 , especially for the high rate capability. At the higher discharge/charge rate (2C), the discharge and charge capacities of 415.5 and 406.1 mAh/g have been obtained for the Li 2.97 Mg 0.03 VO 4 which is more than three times higher the discharge/charge capacities of Li 3 VO 4 . The discharge and charge capacities of pure Li 3 VO 4 are only 126.4 and 125.8 mAh/g respectively. The excellent electrochemical performance of Li 2.97 Mg 0.03 VO 4 enables it as a promising anode material for rechargeable lithium-ion batteries.

In this work, a new non-fullerene electron acceptor (Y8) was synthesized with a fused dithienothiophen [3, 2-b] -pyrrolo benzothiadiazole (TPBT unit with a BT-core) as central unit and two electron-deficient units of 2-(6-fluoro-2, 3-dihydro-3-oxo-1H-inden-1-ylidene) - propanedinitrile (F-IC) as the end groups. Y8 possessed strong absorption in 700–900 nm. The inverted device based on ITO/ZnO/PM6:Y8/MoO3/Ag structure, demonstrated the power conversion efficiency (PCE) up to 14.25% with a short circuit current density (Jsc) of 22.18 mA cm−2 and a high open-circuit voltage (Voc) of 0.88 V. And the optimized device based on PM6:Y8 exhibited relatively high electron mobility (8.7 × 10−4 cm2V−1s−1). These results demonstrated that application of F-IC end group based on small molecule could be a promising measure for improving efficiency of OPVs.

Narrow bandgap n-type organic semiconductors (n-OS) have attracted great attention in recent years as acceptors in organic solar cells (OSCs), due to their easily tuned absorption and electronic energy levels in comparison with fullerene acceptors. Herein, a new n-OS acceptor, Y5, with an electron-deficient-core-based fused structure is designed and synthesized, which exhibits a strong absorption in the 600-900 nm region with an extinction coefficient of 1.24 × 105 cm-1 , and an electron mobility of 2.11 × 10-4 cm2 V-1 s-1 . By blending Y5 with three types of common medium-bandgap polymers (J61, PBDB-T, and TTFQx-T1) as donors, all devices exhibit high short-circuit current densities over 20 mA cm-2 . As a result, the power conversion efficiency of the Y5-based OSCs with J61, TTFQx-T1, and PBDB-T reaches 11.0%, 13.1%, and 14.1%, respectively. This indicates that Y5 is a universal and highly efficient n-OS acceptor for applications in organic solar cells.

Two D–A conjugated polymers containing benzo[1,2-b:4,5-b’] dithiophene (BDT), benzo[1,2-b:4,5-b’]difuran (BDF) donor units and 4,7-di(thiophen-2-yl)-5,6-bis(n-octyloxy)[2,1,3]benzoselenadiazole (DTBSe) acceptor unit, namely PBDTDTBSe and PBDFDTBSe have been synthesized by Stille coupling polymerization. The two polymers show good solubility in common organic solvents, good film forming properties, broad absorption (350–700 nm), low optical band gap (about 1.60 eV) and relatively high hole mobility [1.22 × 10−2 cm−2/(V.s)]. The devices based on the blend film of PBDFDTBSe and PC71BM (1:1, w/w) exhibited the best device performance with PCE of 3.28 %, V oc of 0.71 V, J sc of 10.37 mA cm−2 and FF of 44.6 % under illumination of AM 1.5 G (100 mW cm−2).

A new small molecule acceptor, m‐ITIC‐OR, based on indacenodithieno[3,2‐b]thiophene core with meta‐alkoxyphenyl side chains, is designed and synthesized. The m‐ITIC‐OR film shows broader and redshift absorption compared to its solution and matched energy levels with a hexafluoroquinoxaline‐based polymer donor‐HFQx‐T. Here, polymer solar cells (PSCs) by blending an HFQx‐T donor and an m‐ITIC‐OR acceptor as an active layer deliver the power conversion efficiency (PCE) of 6.36% without any posttreatment. The investigations demonstrate that the HFQx‐T:m‐ITIC‐OR blend films possess higher and more balanced charge mobility, negligible bimolecular recombination, and nanoscale interpenetrating morphology after thermal annealing (TA) treatment. Through a simple TA treatment at 150 °C for 5 min, an impressive PCE of 9.3% is obtained. This efficiency is among one of the highest PCEs for additive free PSCs. This is the first time alkoxyphenyl side chain is introduced into nonfullerene electron acceptor; more interestingly, the new electron acceptor (m‐ITIC‐OR) in this work shows a great potential for highly efficient photovoltaic properties.

Ladder-type conjugated structures with rigid and coplanar molecular frameworks feature longer effective conjugation, affirmative optoelectronic properties and strong intermolecular π–π interactions, which are ideal characteristics for organic photovoltaics. Here, a new “zigzag” angular-fused naphthodifuran (zNDF) based on alkoxyphenyl side chains was designed and synthesized. The distannylated zNDF building block was copolymerized with 4,7-di(5-bromothiophen-2-yl)-5,6-dioctyloxybenzo[c][1,2,5]thiadiazole and 5,8-bis(5-bromothiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)-3-fluorophenyl)-6,7-difloroquinoxaline (Br-BT and Br-ffQx) acceptor units by Stille cross coupling reaction to form two new medium bandgap donor–acceptor polymers PzNDFP-BT and PzNDFP-ffQx, respectively. The photovoltaic properties of the copolymers blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an electron acceptor were investigated. A 6.9% efficiency was achieved from the single device based on the PzNDFP-BT : PC71BM (1 : 1.5, w/w) blend film with a 0.25% 1,8-diiodooctane (DIO) additive, which is among the highest efficiency for zNDF-based polymer solar cells.