Y6 is a new type of non-fullerene acceptor, which has led to power conversion efficiencies of single-junction polymer solar cells over 17% when combined with a careful choice of polymeric donors. However, the excited state characteristics of Y6, which is closely correlated with its opto-electronic applications, are not clear yet. In this work, we studied the excited state properties of the Y6 solution and Y6 film, by using steady-state and time-resolved spectroscopies as well as time-dependent density functional theory (TD-DFT) calculations. UV-Vis absorption and fluorescence simulation, natural transition orbitals (NTOs) and hole-electron distribution analysis of Y6 solution were performed for understanding the excitation properties of Y6 by using TD-DFT calculations. The lifetimes of the lowest singlet excited state in Y6 solution and film were estimated to be 0.98 and 0.8 ns, respectively. Combining the exciton lifetime and photoluminescence (PL) quantum yield, the intrinsic radiative decay lifetimes of Y6 in the solution and film were estimated, which were 1.3 and 10.5 ns for the Y6 solution and film, respectively. Long exciton lifetime (~0.8 ns) and intrinsic radiative decay lifetime (~10.5 ns) of Y6 film enable Y6 to be a good acceptor material for the application of polymer solar cells.

In this work, charge photogeneration dynamics in PTQ10:Y6 solar cells were studied by steady-state and time-resolved spectroscopies. For neat donor and acceptor films, we determined the exciton diffusion coefficients of PTQ10 and Y6 as 1.3 × 10⁻³ cm²·s⁻¹ and 6.8 × 10⁻³ cm²·s⁻¹, respectively. Furthermore, we find the LUMO and HOMO level offsets of 0.14 eV and 0.11 eV are sufficient for the dissociation of donor and acceptor excitons, respectively. For PTQ10:Y6 blend films, we find DIO additive could increase the scales of acceptor and donor phases. The acceptor phase increased slightly from 17.2 nm to 20.0 nm, while the donor phase increased from 2.3 nm to 5.8 nm. In addition, we find bimolecular recombination is a critical form for carrier recombination and DIO additive can significantly suppress the carrier recombination rate of PTQ10:Y6 active layer in an ultrafast time scale. This work is helpful for understanding the charge photogeneration processes in non-fullerene polymer solar cells.

Helically coiled, semiconducting graphenic nanostructures show exceptional promise for nanoelectronics, yet their synthesis has remained challenging due to their inherently strained backbone and the difficulties associated with structural characterization. In this work, we demonstrate the synthesis and characterization of laterally π-extended polyhelicenes (EPHs), achieved through regioselective cyclodehydrogenation. Spectroscopic and microscopic analyses, including mass spectrometry, solid-state NMR, scanning-probe microscopy, and transmission electron microscopy, confirm the well-defined helical, layered architecture of the EPHs. Ultrafast terahertz spectroscopy reveals pronounced intrahelix photoconductivity, demonstrating their potential as carbon-based nanoscale conductors. The scalable synthetic approach described in this work unlocks the application potential of carbon-based helical nanostructures, paving the way for nanoinductors in nanoscale solenoids, spin-selective electronics, and future high-frequency nanoelectronic devices.

Owing to their unique optical and electronic properties, vertical van der Waals heterostructures (vdWHs) have attracted considerable attention in optoelectronic applications, such as photodetection, light harvesting, and light-emitting diodes. To fully harness these properties, it is crucial to understand the interfacial charge transfer (CT) and recombination dynamics across vdWHs. However, the effects of interfacial energetics and defect states on interfacial CT and recombination processes in graphene-transition metal dichalcogenide (Gr-TMD) vdWHs remain debated. Here, we investigate the interfacial CT dynamics in Gr-TMD vdWHs with different chemical compositions (W, Mo, S, and Se) and tunable interfacial energetics. We demonstrate, using ultrafast terahertz spectroscopy, that while the photo-induced electron transfer direction is universal with graphene donating electrons to TMDs, its efficiency is chalcogen-dependent: the CT efficiency of S atom-based vdWHs is 3–5 times higher than that of Se-based vdWHs thanks to the lower Schottky barrier present in S-based vdWHs. In contrast, the electron back transfer process from TMD to Gr, which defines the charge separation time, is transition metal-dependent and dominated by the mid-gap defect level of TMDs: W transition metal-based vdWHs possess extremely long charge separation, well beyond 1 ns, which is significantly longer than Mo-based vdWHs with only 10 s of ps charge separation. This difference can be traced to the much deeper mid-gap defect reported in W-based TMDs compared to Mo-based ones, resulting in modified energetics for the back electron transfer from the trapped states to graphene. Our results shed light on the role of interfacial energetics and defects by tailoring chemical compositions of TMDs on the interfacial CT and recombination dynamics in Gr-TMD vdWHs, which is pivotal for optimizing optoelectronic devices, particularly in the field of photodetection.

Polydisperse edge‐fused nickel(II) porphyrin nanoribbons have been synthesized by Yamamoto coupling followed by gold(III)‐mediated fusion, with average degrees of polymerization of up to 37 repeat units (length 31 nm). Time‐resolved optical‐pump terahertz spectroscopy measurements indicate that photo‐generated charge carriers have dc mobilities of up to 205 cm² V⁻¹ s⁻¹ in these nanoribbons, exceeding the values previously reported for most other types of nanoribbon or π‐conjugated polymer.