We demonstrate a facile and green approach to preparing a vanadium oxide hydrate (VOx·nH2O) layer to serve as the hole-transport layer (HTL) in high-performance polymer solar cells (PSCs). The VOx·nH2O layer was in situ prepared by a combined H2O2 and ultraviolet-ozone (UVO) processing on a VOx layer. The as-prepared VOx·nH2O layer featured a work function of 5.0 ± 0.1 eV, high transmittance, and better interface properties compared to those of the generally prepared VOx (UVO or thermal annealing) layers. PSCs based on poly[(ethylhexyl-thiophenyl)-benzodithiophene-(ethylhexyl)-thienothiophene]/[6,6]-phenyl-C71-butyric acid methyl ester using the VOx·nH2O layer as the HTL yielded high power conversion efficiencies (PCEs) up to 8.11%, outperforming the devices with VOx layers (PCE of 6.79% for the UVO-processed VOx layer and 6.10% for the thermally annealed VOx layer) and conventional polyethylenedioxythiophene–polystyrenesulfonate (PEDOT:PSS) layers (PCE of 7.67%). The improved PCE was attributed to the enhanced JSC and/or fill factor, which mainly correlate to the improved interfacial contact between the photoactive layer and the indium tin oxide/HTL or cathode when using the VOx·nH2O layer as the HTL. A similar improvement in the PCE was also observed for the PSCs based on poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester. In addition, PSCs with a VOx·nH2O layer as the HTL showed a higher stability than that of those with a PEDOT:PSS layer. Hence, it would be possible to use this simply and in situ prepared VOx·nH2O layer as an inexpensive HTL for high-performance PSCs.Keywords: H2O2−UVO processing; hole-transport layer; interfacial contact; Polymer solar cells; vanadium oxide hydrate;

Clusterfullerenes with variable carbon cages have been extensively studied in recent years. However, despite all these efforts, C74 cage-based clusterfullerene remains a missing piece of the puzzle. Herein, we show that single-crystal X-ray crystallographic analysis unambiguously assigns the previously reported dimetallofullerene Sc2@C76 to a novel carbide clusterfullerene, Sc2C2@D3h(14246)-C74, the first experimentally proven clusterfullerene with a C74 cage. In addition, Sc2C2@D3h(14246)-C74 was charaterized by mass spectrometry, ultraviolet–visible–near-infrared absorption spectroscopy, 45Sc nuclear magnetic resonance, and cyclic voltammetry. Comparative studies of the motion of the carbide cluster in Sc2C2@D3h(14246)-C74 and Sc2C2@C2n (n = 40−44) revealed that a combination of factors, involving both the shape and size of the cage, is crucial in dictating the cluster motion. Moreover, structural studies of D3h(14246)-C74 revealed that it can be easily converted to Cs(10528)-C72 and Td(19151)-C76 cages via C2 desertion/insertion and Stone–Wales transformation. This suggests that D3h(14246)-C74 might play an important role in the growth pathway of clusterfullerenes.

Novel types of N,S,P-codoped carbons with varied nanostructures are developed as efficient and stable electrocatalysts for the oxygen reduction reaction (ORR). The carbon catalysts were facilely prepared using poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanospheres as single precursors through a pyrolysis procedure in the presence or absence of melamine. The as-prepared microporous carbon nanospheres NSP-PC-1 with a high surface area (967 m2 g−1) exhibit a significantly enhanced ORR catalytic activity compared to their solely N-doped counterpart (N-PC-1), suggesting the remarkable contribution of additional S,P-doping on the ORR performance. More importantly, the as-prepared mesoporous carbon nanosheets NSP-PC-2 with a moderately high surface area (613 m2 g−1) and comparable overall NSP content show greatly improved ORR catalytic activity relative to that of NSP-PC-1, which is even slightly superior to that of commercial Pt/C catalysts. The excellent performance of NSP-PC-2 is mainly attributed to its proper N,S,P-codoping as well as advanced structural features.

By introducing CO2 as the oxygen source during the arcing process, a new isomer of Sc2O@C82, Sc2O@C3v(8)-C82, previously investigated only by computational studies, was discovered and characterized by mass spectrometry, UV–vis–NIR absorption spectroscopy, cyclic voltammetry, 45Sc NMR, density functional theory (DFT) calculations, and single-crystal X-ray diffraction. The crystallographic analysis unambiguously elucidated that the cage symmetry was assigned to C3v(8) and suggests that Sc2O cluster is disordered inside the cage. The comparative studies of crystallographic data further reveal that the Sc1–O–Sc2 angle is in the range of 131.0–148.9°, much larger than that of the Sc2S@C3v(8)-C82, demonstrating a significant flexibility of dimetallic clusters inside the cages. The electrochemical studies show that the electrochemical gap of Sc2O@C3v(8)-C82 is 1.71 eV, the largest among those of the oxide cluster fullerenes (OCFs) reported so far, well correlated with its rich abundance in the reaction mixture of OCF synthesis. Moreover, the comparative electrochemical studies suggest that both the dimetallic clusters and the cage structures have major influences on the electronic structures of the cluster fullerenes. Computational studies show that the cluster can rotate and change the Sc–O–Sc angle easily at rather low temperature.

It has been proposed that the fullerene formation mechanism involves either a top-down or bottom-up pathway. Despite different starting points, both mechanisms approve that particular fullerenes or metallofullerenes are formed through a consecutive stepwise process involving Stone–Wales transformations (SWTs) and C2 losses or additions. However, the formation pathway has seldomly been defined at the atomic level due to the missing-link fullerenes. Herein, we present the isolation and crystallographic characterization of two isomeric clusterfullerenes Sc2O@C2v(3)-C78 and Sc2O@D3h(5)-C78, which are closely related via a single-step Stone–Wales (SW) transformation. More importantly, these novel Sc2O@C78 isomers represent the key links in a well-defined formation pathway for the majority of solvent-extractable clusterfullerenes Sc2O@C2n (n = 38–41), providing molecular structural evidence for the less confirmed fullerene formation mechanism. Furthermore, DFT calculations reveal a SWT with a notably low activation barrier for these Sc2O@C78 isomers, which may rationalize the established fullerene formation pathway. Additional characterizations demonstrate that these Sc2O@C78 isomers feature different energy bandgaps and electrochemical behaviors, indicating the impact of SW defects on the energetic and electrochemical characteristics of metallofullerenes.

Besides the conventional D5h(8149)-C70 fullerene, there are a large number of C70 isomers that violate the isolated pentagon rule (IPR). However, these non-IPR C70 fullerenes have been less investigated owing to their low stabilities or high reactivities. In this study, we report for the first time the X-ray structure of an unconventional endohedral C70 fullerene, Sc2O@C2(7892)-C70. The combined study of geometrical analysis and computation further reveals the ionic and covalent interactions between the cluster and the cage, both of which contribute to the stabilization of this non-IPR C70 fullerene. In addition, a close structural relationship between the non-IPR C2(7892)-C70 and the IPR D5h(8149)-C70 has been demonstrated, which might provide an alternative explanation of the formation of non-IPR fullerenes.

•The K4PTC and its composite (rGO-K4PTC) are used as alternatives to the Ca ETL.•K4PTC and rGO-K4PTC exhibit low WF of 4.0 eV, matching the LUMO level of acceptors.•P3HT and PTB7-th-based devices with respective ETLs yield increases of ∼35% in PCE.•PSCs with the rGO-K4PTC ETL exhibit better stability under degradation tests in air.The polymer solar cell (PSC) with Ca/Al electrode always suffers from low stability mainly due to the incorporation of oxygen and moisture-sensitive Ca electron-transport interlayer (ETL). To alleviate this problem, air-stable alternatives to Ca ETL are highly desired. Herein, we report two solution-processable, air-stable, effective and inexpensive ETLs based on potassium-neutralized perylene tetracarboxylic derivative (K4PTC) and its rGO composite (rGO-K4PTC), respectively. These ETL materials were facilely prepared and characterized by means of UV-vis, FL, FTIR, XPS and UPS. Importantly, both ETLs exhibited a low work function (WF) of 4.0 eV, which well matches the LUMO level of fullerene acceptors and allows their use as ETL in PSCs. As a result, the P3HT and PTB7-th-based devices with respective ETL remarkably outperformed those without ETL yielding increases of ∼35% in power conversion efficiencies (PCEs), which indicates good electron-transporting capabilities of K4PTC and rGO-K4PTC interlayers. The high-performance PSCs with the ETL gave average PCEs of 6.17–6.18% (for PTB7-th:PC61BM-based devices) and 7.26% (for PTB7-th:PC71BM-based devices), respectively, fairly comparable to those of Ca/Al devices (6.50% and 7.50%). Furthermore, the rGO-K4PTC device exhibited stability higher than that of the K4PTC device probably due to the fact that the rGO-K4PTC layer can provide more efficient protection for the active layer against degradation. Thus, rGO-K4PTC layer might be more suitable for real applications as compared to the K4PTC layer.

•We prepared novel bimetallic Cu-Au NPs with core-shell nanostructures.•The Cu-Au NPs exhibited broad-band LSPR absorption at wavelengths of 550–850 nm.•The incorporation of Cu-Au NPs improved the light harvesting efficiency of OSC.•The performance of Cu-Au NPs-embedding OSCs increased by up to 13.4%.In this work, a facile preparation of Cu-Au bimetallic nanoparticles (NPs) with core-shell nanostructures is reported. Importantly, as-prepared Cu-Au NPs are highly stable, solution-processable and exhibit a broad localized surface plasmon resonance (LSPR) band at long wavelengths of 550–850 nm. Highly efficient plasmonic organic solar cells (OSCs) were fabricated by embedding Cu-Au NPs in an anodic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer. The average power conversion efficiency (PCE) was enhanced from 3.21% to 3.63% for poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PC61BM) based devices, from 6.51% to 7.13% for poly[(ethylhexyl-thiophenyl)-benzodithiophene -(ethylhexyl)-thienothiophene](PTB7-th):PC61BM based devices and from 7.53% to 8.48% for PTB7-th:PC71BM based devices, corresponding to 9.5–13.4% PCE improvement. Such an improvement is very comparable to that (12.5%) obtained in those with plasmonic Au NPs but achieved at lower cost. This study thus demonstrates a novel and cost-effective approach to enhance the photovoltaic performance of OSCs, in combination with the broad-band plasmonic Cu-Au bimetallic nanostructures.

Continuous ITQ-16 and ITQ-17 films on silicon wafer were prepared in fluoride media using TEAOH as organic structure-directing agent. The proportion of polymorph C in the as-synthesized ITQ-16 and ITQ-17 films was determined via X-ray diffraction characterization. The proportion of polymorph C in the ITQ-16 and ITQ-17 films was controlled via optimizing the compositions of the reaction mixtures and reaction conditions, such as varying the Si/Ge molar ratio and adding n-propyl alcohol as a solvent in the reaction mixture. The Ge atoms in the reaction media strongly increased the crystallization of polymorph C in ITQ-16 and ITQ-17 films. Moreover, the stabilizing and buffering effect of n-propyl alcohol on crystal growth further enhanced the proportion of polymorph C in the ITQ-16 and ITQ-17 films. For potential catalytic applications, Al was incorporated into the framework of polymorph C, and a pure phase of polymorph C in Al-ITQ-17 film was achieved from the synthesis gel in the n-propyl alcohol phase.

A series of nitrogen enriched microporous carbons were facilely prepared by KOH activation using melamine-doped phenolic resins as precursors. The activated carbons show high CO2 uptakes up to ca. 1.3 mmol g−1 under low pressure (0.15 bar, 25 °C), which can be ascribed to not only their optimal fraction of ultramicropores but also the high N-contents. One of the samples even exhibits excellent adsorption selectivity for CO2 over N2 (i.e., selectivity factors of 43.7 and 52.9 obtained from initial slope and IAST calculations, respectively). Furthermore, the preferential CO2 uptake of the carbons was confirmed by successive breakthrough experiments under post combustion flue gas stream conditions (15% CO2 concentration, 1 bar and 25 °C). Since these carbons also feature good stability over repeated thermal cycling and ease of regeneration, their practical applications in post combustion CO2 capture shall lie within the realm of possibility.

A series of fulleropyrrolidine derivatives (FPx, x = 1–8) with alternating N-phenyl or N-methyl group were prepared as acceptors for polymer solar cells (PSCs) with the purpose of investigating the effect of N-substitutions on the photovoltaic properties of fullerene materials. More importantly, the morphology studies by means of atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and space charge limited current (SCLC) measurements revealed that FP1 with N-phenyl group possessed not only appropriate miscibility with P3HT but also high electron mobility, which may account for its optimal photovoltaic properties.

A new oxide cluster fullerene, Sc2O@C2v(5)-C80, has been isolated and characterized by mass spectrometry, UV–vis–NIR absorption spectroscopy, cyclic voltammetry, 45Sc NMR, DFT calculations, and single crystal X-ray diffraction. The crystallographic analysis unambiguously elucidated that the cage symmetry was assigned to C2v(5)-C80 and suggests that the Sc2O cluster is ordered inside the cage. The crystallographic data further reveals that the Sc1–O–Sc2 angle is much larger than that found in Sc2O@Td(19151)-C76 but almost comparable to that in Sc2O@Cs(6)-C82, suggesting that the endohedral Sc2O unit is flexible and can display large variation in the Sc–O–Sc angle, which depends on the size and shape of the cage. Computational studies show that there is a formal transfer of four electrons from the Sc2O unit to the C80 cage, i.e., (Sc2O)4+@(C80)4–, and the HOMO and LUMO are mainly localized on the C80 framework. Moreover, thermal and entropic effects are seen to be relevant in the isomer selection. Comparative studies between the recently reported Sc2C2@C2v(5)-C80 and Sc2O@C2v(5)-C80 reveal that, despite their close structural resemblance, subtle differences exist on the crystal structures, and the clusters exert notable impact on their spectroscopic properties as well as interactions between the clusters and corresponding cages.

Two Sm@C82 isomers have been well characterized for the first time by means of 13C NMR spectroscopy, and their structures were unambiguously determined as Sm@C2v(9)-C82 and Sm@C3v(7)-C82, respectively. A combined study of single crystal X-ray diffraction and theoretical calculations suggest that in Sm@C2v(9)-C82 the preferred Sm2+ ion position shall be located in a region slightly off the C2 axis of C2v(9)-C82. Moreover, the electrochemical surveys on these Sm@C82 isomers reveal that their redox activities are mainly determined by the properties of their carbon cages.

Although a non-IPR fullerene cage is common for endohedral cluster fullerenes, it is very rare for conventional endofullerenes M@C2n, probably because of the minimum geometry fit effect of the endohedral single metal ion. In this work, we report on a new non-IPR endofullerene Sm@C2v(19138)-C76, including its structural and electrochemical features. A combined study of single-crystal X-ray diffraction and DFT calculations not only elucidates the non-IPR cage structure of C2v(19138)-C76 but also suggests that the endohedral Sm2+ ion prefers to reside along the C2 cage axis and close to the fused pentagon unit in the cage framework, indicative of a significant metal–cage interaction, which alone can stabilize the non-IPR cage. Furthermore, electrochemical studies reveal the fully reversible redox behaviors and small electrochemical gap of Sm@C2v(19138)-C76, which are comparable to those of IPR species Sm@D3h-C74.

An extensive family of oxide cluster fullerenes (OCFs) Sc2O@C2n (n = 35–47) has been facilely produced for the first time by introducing CO2 as the oxygen source. Among this family, Sc2O@C70 was identified as the smallest OCF and therefore isolated and characterized by mass spectrometry, 45Sc nuclear magnetic resonance, UV–vis–near-infrared absorption spectroscopy, cyclic voltammetry, and density functional theory calculations. The combined experimental and computational studies reveal a non-isolated pentagon rule isomer Sc2O@C2(7892)–C70 with reversible oxidative behavior and lower bandgap relative to that of Sc2S@C2(7892)–C70, demonstrating a typical example of unexplored OCF and underlining its cluster-dependent electronic properties.

We report the synthesis, isolation, and characterizations of the novel trimetallofullerene Sm3@Ih-C80. Importantly, the experimental X-ray structure of Sm3@Ih-C80 verified for the first time that three metal atoms can be stabilized in a fullerene cage without a nonmetal mediator. Furthermore, computational studies demonstrated the electronic features of Sm3@Ih-C80, which are similar to that of theoretically studied Y3@Ih-C80. Electrochemical studies of Sm3@Ih-C80 showed a major difference from those of the well-studied isoelectronic species Sc3N@Ih-C80 and La2@Ih-C80.

The dream target of artificial photosynthesis is the realization of long-lived radical ion pair states that power catalytic centers and, consequently, the production of solar fuels. Notably, magnetic field effects, especially internal magnetic field effects, are rarely employed in this context. Here, we report on a linear Lu3N@Ih-C80–PDI electron donor–acceptor conjugate, in which the presence of the Lu3N cluster exerts an appreciable electron nuclear hyperfine coupling on the charge transfer dynamics. As such, a fairly efficient radical ion pair intersystem crossing converts the initially formed singlet radical ion pair state, 1[(Lu3N@Ih-C80)•+–PDI•–], to the corresponding triplet radical ion pair state, 3[(Lu3N@Ih-C80)•+–PDI•–]. Most notably, the radical ion pair state lifetime of the latter is nearly 1000 times longer than that of the former.

A metallofullerene Sm@D3h-C74 that contains a divalent rare-earth metal has been studied structurally and electrochemically. The crystallographic analysis revealed that the endohedral Sm atom is more or less motional rather than being localized at a site where the pyracylene motif is nearby. This suggests a weaker metal–pyracylene interaction in Sm@D3h-C74 relative to that in MII@C74 (M = Group II metal), thus confirming the importance of the metal variety. The electrochemical studies showed a major difference between the redox properties of Sm@D3h-C74 and other Sm-fullerenes and indicated a small band gap for the title compound.

A new metallofullerene Sm@C2v(3)-C80 was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C2v(3)-C80 and Yb@C2v(3)-C80 revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles.

Besides the conventional D5h(8149)-C70 fullerene, there are a large number of C70 isomers that violate the isolated pentagon rule (IPR). However, these non-IPR C70 fullerenes have been less investigated owing to their low stabilities or high reactivities. In this study, we report for the first time the X-ray structure of an unconventional endohedral C70 fullerene, Sc2O@C2(7892)-C70. The combined study of geometrical analysis and computation further reveals the ionic and covalent interactions between the cluster and the cage, both of which contribute to the stabilization of this non-IPR C70 fullerene. In addition, a close structural relationship between the non-IPR C2(7892)-C70 and the IPR D5h(8149)-C70 has been demonstrated, which might provide an alternative explanation of the formation of non-IPR fullerenes.