Dibenzothiophene-S,S-dioxide and Bispyridinium-Based Cationic Polyfluorene Derivative as an Efficient Cathode Modifier for Polymer Solar Cells

Dibenzothiophene S, S-Dioxide-Containing Dipolar Molecules As Efficient Hole-Transport Materials for p-i-n Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells (OIH-PSCs) have developed rapidly in the past decade, and the commercialization of OIH-PSCs demands low-cost hole-transport materials (HTMs) with high performance and stability. The present study synthesized two organic HTMs containing dibenzothiophene S-dioxide as the acceptor unit and triphenylamine as the donor (denoted by TPAF-SO2 and TPA-SO2). In TPAF-SO2, the methoxy group and adjacent fluorine atom were introduced to decrease the highest occupied molecular orbital energy level. In TPA-SO2, the methyl sulfide group is the end group that can passivate the lead ion. TPAF-SO2 and TPA-SO2 exhibit hole-transport mobilities as high as 1.12 × 10-3 and 2.31 × 10-3 cm2 v-1 s-1, respectively, and strongly passivate Pb vacancies. Compared with TPAF-SO2, TPA-SO2 is more suitable for the growth of perovskite crystals. The perovskite grown on the latter has a lower trap density and higher carrier mobility; thus, both the nonradiative recombination and the charge-transport loss are decreased. The OIH-PSC based on TPA-SO2 as the HTM achieved a power conversion efficiency (PCE) as high as 22.08%, whereas the device based on TPAF-SO2 achieved a PCE of only 18.42%. In addition, the unencapsulated device based on TPA-SO2 can maintain 85% of the initial PCE after being stored in N2 for 1200 h, whereas the device based on TPAF-SO2 decayed rapidly to zero in 800 h under the same conditions.

Achieving Bright Organic Light-Emitting Field-Effect Transistors with Sustained Efficiency through Hybrid Contact Design

Organic light-emitting field-effect transistors (OLEFETs) with bilayer structures have been widely studied due to their potential to integrate high-mobility organic transistors and efficient organic light-emitting diodes. However, these devices face a major challenge of imbalance charge transport, leading to a severe efficiency roll-off at high brightness. Here, we propose a solution to this challenge by introducing a transparent organic/inorganic hybrid contact with specially designed electronic structures. Our design aims to steadily accumulate the electrons injected into the emissive polymer, allowing the light-emitting interface to effectively capture more holes even when the hole current increases. Our numerical simulations show that the capture efficiency of these steady electrons will dominate charge recombination and lead to a sustained external quantum efficiency of 0.23% over 3 orders of magnitude of brightness (4 to 7700 cd/m²) and current density (1.2 to 2700 mA/cm²) from -4 to -100 V. The same enhancement is retained even after increasing the external quantum efficiency (EQE) to 0.51%. The high and tunable brightness with stable efficiency offered by hybrid-contact OLEFETs makes them ideal light-emitting devices for various applications. These devices have the potential to revolutionize the field of organic electronics by overcoming the fundamental challenge of imbalance charge transport.

Efficient Cathode Buffer Material Based on Dibenzothiophene-S,S-dioxide for Both Conventional and Inverted Organic Solar Cells

A novel conjugated molecule (PBSON) based on a main chain composed of bis(dibenzothiophene-S,S-dioxide) fused cyclopentadiene and side chains containing amino groups is presented as an efficient cathode buffer material (CBM) for organic solar cells (OSCs). PBSON showed a deep highest occupied molecular orbital (HOMO) energy level of -6.01 eV, which was beneficial for building hole-blocking layers at the cathodes of OSCs. The energy bandgap of PBSON reached 3.17 eV, implying high transmittance to visible and near-infrared light, which meant PBSON should be suitable for the applications to most inverted OSCs. The scanning Kelvin probe microscopy measurement and theoretical calculation on the PBSON/cathode interfacial interaction proved the excellent work function-regulating abilities of PBSON for various cathodes, suggesting that PBSON could promote the formation of Ohmic contacts at the cathodes and thus improve the transport and collection of electron carriers for OSCs. The characterization of electron-only devices demonstrated the good electron-transporting performance of PBSON at the cathodes. In the conventional OSCs, it was hinted that PBSON might restrain the infiltrations of evaporated cathode atoms into the active films, consequently reducing the reverse leakage currents. As a result, PBSON was able to boost the power conversion efficiencies (PCEs) by 58.2 and 56.4% for both conventional and inverted OSCs of the typical PTB7:PC71BM system, respectively, as compared to the unadorned devices. In terms of the classical PTB7-Th:PC71BM system, substantial increases in PCEs could also be found with PBSON interlayers, which were 54.7 and 59.8% for the conventional device and inverted device, respectively. Therefore, PBSON is a kind of promising CBM for realizing both conventional and inverted OSCs of high performance.

Origin of the Additive-Induced VOC Change in Non-Fullerene Organic Solar Cells

Additives are often used to adjust the morphology of the active layer to improve the performance of organic solar cells (OSCs). Here, taking typical high-efficiency non-fullerene systems as examples, the effect of the additive on the device performance in non-fullerene OSCs is systematically investigated. Surprisingly, an unpresented V_OC change is observed in the opposite direction of the two typical systems (PM6:Y6 and PTB7-Th: ITIC) appearing after the incorporation of the additive DIO, which can be affected by the morphological differences as indicated by the several morphological studies. The bewildering V_OC change caused by the additive in different material systems is supposed to originate from the different energy level variations as verified by the energy level studies. Molecular dynamic (MD) and density functional theory (DFT) calculations are also included to get an insight into the dynamic of the additive-induced morphological differences that are supposed to contribute to the energy level changes. Combining a series of morphological and energic studies as well as the theoretical calculations, the origin of unforeseeable V_OC changes caused by additives in non-fullerene OSCs is clarified, and provides in-depth insights into the effects of additives on device performance.

Crystal structures of 3-halo-2-organochalcogenylbenzo[b]chalcogenophenes

The structure of the title compounds 3-bromo-2-(phenyl-sulfan-yl)benzo[b]thiophene (C14H9BrS2; 1), 3-iodo-2-(phenyl-sulfan-yl)benzo[b]thio-phene (C14H9IS2; 2), 3-bromo-2-(phenyl-selan-yl)benzo[b]seleno-phene (C14H9BrSe2; 3), and 3-iodo-2-(phenyl-selan-yl)benzo[b]seleno-phene (C14H9ISe2; 4) were determined by single-crystal X-ray diffraction; all structures presented monoclinic (P21/c) symmetry. The phenyl group is distant from the halogen atom to minimize the steric hindrance repulsion for all structures. Moreover, the structures of 3 and 4 show an almost linear alignment of halogen-selenium-carbon atoms arising from the intra-molecular orbital inter-action between a lone pair of electrons on the halogen atom and the anti-bonding σ*Se-C orbital (n halogen→σ*Se-C). This inter-action leads to significant differences in the three-dimensional packing of the mol-ecules, which are assembled through π-π and C-H⋯π inter-actions. These data provide a better comprehension of the inter-molecular packing in benzo[b]chalcogenophenes, which is relevant for optoelectronic applications.

Alcohol-soluble fluorene derivate functionalized with pyridyl groups as a high-performance cathode interfacial material in organic solar cells

The synthesis and application as a cathode interlayer in organic photovoltaics of a fluorene derivative with pyridyl functional chains are presented.

Synthesis of 2-Organylchalcogenopheno[2,3-b]pyridines from Elemental Chalcogen and NaBH4 /PEG-400 as a Reducing System: Antioxidant and Antinociceptive Properties

An alternative method to prepare 2-organylchalcogenopheno[2,3-b]pyridines was developed by the insertion of chalcogen species (selenium, sulfur or tellurium), generated in situ, into 2-chloro-3-(organylethynyl)pyridines by using the NaBH₄ /PEG-400 reducing system, followed by an intramolecular cyclization. It was possible to obtain a series of compounds with up to 93 % yield in short reaction times. Among the synthesized products, 2-organyltelluropheno[2,3-b]pyridines have not been described in the literature so far. Moreover, the compounds 2-phenylthieno[2,3-b]pyridine (3 b) and 2-phenyltelluropheno[2,3-b]pyridine (3 c) exhibited significant antioxidant potential in different in vitro assays. Further studies demonstrated that compound 3 b exerted an antinociceptive effect in acute inflammatory and non-inflammatory pain models, thus indicating the involvement of the central and peripheral nervous systems on its pharmacological action. More specifically, our results suggest that the intrinsic antioxidant property of compound 3 b might contribute to attenuating the nociception and inflammatory process on local injury induced by complete Freund's adjuvant (CFA).

Dibenzothiophene-S,S-dioxide-bispyridinium-fluorene-based polyelectrolytes for cathode buffer layers of polymer solar cells

The successful applications of PFSOPyCl and its newly synthesized derivative PFSOPyCl-E cathode modifiers in inverted polymer solar cells are presented.

Molecular Engineering on Bis(benzothiophene-S,S-dioxide)-Based Large-Band Gap Polymers for Interfacial Modifications in Polymer Solar Cells

The development of effectively universal interfacial materials for both conventional and inverted polymer solar cells (PSCs) plays a very crucial role in achieving highly photovoltaic performance and feasible device engineering. In this study, two novel alcohol-soluble conjugated polymers (PBSON-P and PBSON-FEO) with bis(benzothiophene-S,S-dioxide)-fused aromatics (FBTO) as the core unit and amino as functional groups are synthesized. They are utilized as universal cathode interfacial layers for both conventional and inverted PSCs simultaneously. Ascribing to the enlarged conjugated planarity and higher electron affinity for an FBTO unit, both PBSON-P and PBSON-FEO exhibit versatile electron-transporting abilities. They show wide band gaps that are important for light absorption in inverted PSCs, at which point PBSON-P and PBSON-FEO are more progressive than some of the reported small band gap cathode interfacial materials. Importantly, PBSON-P and PBSON-FEO display deep highest occupied molecular orbital energy levels, which can block holes at the cathode and thus increase the fill factor. As a result, both conventional and inverted PSCs using PBSON-P and PBSON-FEO as cathode interlayers realize high photovoltaic performance. Therefore, this series of novel polymers are amphibious cathode interfacial materials for high-performance conventional and inverted PSCs.

Synthesis of 2,3-bis-organochalcogenyl-benzo[b]chalcogenophenes promoted by Oxone®

We report here an alternative and tunable metal-free synthesis of benzo[b]chalcogenophenes via the electrophilic cyclization of 2-functionalized chalcogenoalkynes promoted by Oxone®.

Pyridine-incorporated alcohol-soluble neutral polyfluorene derivatives as efficient cathode-modifying layers for polymer solar cells

A class of novel alcohol-soluble polyfluorene derivatives with a pyridine group incorporating at the side chains of fluorene is developed to modify the cathode interfaces of both conventional and inverted polymer solar cells.