Highly polarized single-crystal organic light-emitting devices with low turn-on voltage and high brightness.

Linearly-polarized organic electroluminescent devices have gained significant attention due to their potential applications across various fields. However, traditional thin-film organic light-emitting diodes (OLEDs) face significant challenges, primarily due to the necessity of incorporating complex optical elements. In this study, we present linearly-polarized OLEDs (LP-OLEDs) based on organic single crystals that we have designed and prepared.

Fully Non-Fused Ring Electron Acceptors Enable Effective Additive-Free Organic Solar Cells with Enhanced Exciton Diffusion Length.

Low-cost photovoltaic materials and additive-free, non-halogenated solvent processing of photoactive layers are crucial for the large-scale commercial application of organic solar cells (OSCs). However, high-efficiency OSCs that possess all these advantages remain scarce due to the lack of insight into the structure-property relationship. In this work, three fully non-fused ring electron acceptors (NFREAs), DTB21, DTB22, and DTB23, are reported by utilizing a simplified 1,4-di(thiophen-2-yl)benzene (DTB) core with varied alkoxy chain lengths on the thiophene bridge.

Spin-Valley-Locked Electroluminescence for High-Performance Circularly Polarized Organic Light-Emitting Diodes.

Circularly polarized (CP) organic light-emitting diodes (OLEDs) have attracted attention in potential applications, including novel display and photonic technologies. However, conventional approaches cannot meet the requirements of device performance, such as high dissymmetry factor, high directionality, narrowband emission, simplified device structure, and low costs. Here, we demonstrate spin-valley-locked CP-OLEDs without chiral emitters but based on photonic spin-orbit coupling, where photons with opposite CP characteristics are emitted from different optical valleys.

Molecular Orientation-Dependent Photonic Polarization Engineering in Organic Single-Crystal-Filled Microcavities.

Designing the polarization degree of freedom of light is crucial in many fields and has widespread application in, for example, all-optical circuits. In this work, we find that in an organic microcavity filled with anisotropic single crystals the cavity modes can be modulated to be elliptically polarized, i.e.

Molecular Design of Fully Nonfused Acceptors for Efficient Organic Photovoltaic Cells.

The nonfused thiophene-benzene-thiophene (TBT) unit offers advantages in obtaining low-cost organic photovoltaic (OPV) materials due to its simple structure. However, OPV cells, including TBT-based acceptors, exhibit significantly lower energy conversion efficiencies. Here, we introduce a novel approach involving the design and synthesis of three TBT-based acceptors by substituting different position-branched side chains on the TBT unit.

Photochemical Reaction Enabling the Engineering of Photonic Spin-Orbit Coupling in Organic-Crystal Optical Microcavities.

The control and active manipulation of spin-orbit coupling (SOC) in photonic systems are fundamental in the development of modern spin optics and topological photonic devices. Here, we demonstrate the control of an artificial Rashba-Dresselhaus (RD) SOC mediated by photochemical reactions in a microcavity filled with an organic single crystal of photochromic phase-change character. Splitting of the circular polarization components of the optical modes induced by photonic RD SOC is observed experimentally in momentum space.

Organic laser power converter for efficient wireless micro power transfer.

Wireless power transfer with collimated power transmission and efficient conversion provides an alternative charging mode for off-grid and portable micro-power electronics. However, charging micro-power electronics with low photon flux can be challenging for current laser power converters. Here we show laser power converters with organic photovoltaic cells with good performance for application in laser wireless power transfer.

An Ortho-Bisalkyloxylated Benzene-Based Fully Non-fused Electron Acceptor for Efficient Organic Photovoltaic Cells.

To develop the low-cost nonfullerene acceptors (NFAs), two fully non-fused NFAs (TBT-2 and TBT-6) with ortho-bis((2-ethylhexyl)oxy)benzene unit and different side chains onto thiophene-bridges are synthesized through highly efficient synthetic procedures. Both acceptors show good planarity, low optical gaps (≈1.51 eV), and deep highest occupied molecular orbital levels (≤-5.

Large Steric Hindrance Enhanced Molecular Planarity for Low-Cost Non-Fused Electron Acceptors.

Designing efficient non-fused ring electron acceptors is of great importance in decreasing the material cost of organic photovoltaic cells (OPVs). It is a challenge to construct a planar molecular skeleton in non-fused molecules as there are many torsions between adjacent units. Here, we design two non-fused electron acceptors based on bithieno[3,2-]thiophene units as core structures and study the impact of steric hindrance of substituents on molecular planarity.

New Method for Preparing ZnO Layer for Efficient and Stable Organic Solar Cells.

Owing to outstanding optoelectronic properties and simple preparation, zinc oxide (ZnO) has widely been used in organic solar cells (OSCs). Although versatile cathode interface materials have been designed in past, ZnO remains indispensable owing to its excellent overall performance. Therefore, solving the persistent problem of residual amine reacting with non-fullerene acceptors will make ZnO superior over other materials, and thus improve the performance and energy budget of OSCs.

A Medium-Bandgap Nonfullerene Acceptor Enabling Organic Photovoltaic Cells with 30% Efficiency under Indoor Artificial Light.

The correlation between molecular structure and photovoltaic performance is lagging for constructing high-performance indoor organic photovoltaic (OPV) cells. Herein, this relationship is investigated in depth by employing two medium-bandgap nonfullerene acceptors (NFAs). The newly synthesized NFA of FTCCBr exhibits a similar bandgap and molecular energy level, but a much stronger dipole moment and larger average electrostatic potential (ESP) compared with ITCC.

Benchmarking of Density Functionals for the Description of Optical Properties of Newly Synthesized π-Conjugated TADF Blue Emitters.

Computational modeling of the optical characteristics of organic molecules with potential for thermally activated delayed fluorescence (TADF) may assist markedly the development of more efficient emitting materials for organic light-emitting diodes. Recent theoretical studies in this area employ mostly methods from density functional theory (DFT). In order to obtain accurate predictions within this approach, the choice of a proper functional is crucial.

A High-Performance Nonfused Wide-Bandgap Acceptor for Versatile Photovoltaic Applications.

Wide-bandgap (WBG) nonfullerene acceptors (NFAs) with nonfused conjugated structures play a critical role in organic photovoltaic (OPV) cells. Here, NFAs named GS-OEH, GS-OC6, and GS-ISO, with optical bandgaps larger than 1.70 eV, are synthesized without using the fused ring structures.

A Universal Nonhalogenated Polymer Donor for High-Performance Organic Photovoltaic Cells.

Nonhalogenated polymers have great potential in the commercialization of organic photovoltaic (OPV) cells due to their advantage in low-cost preparation. However, non-halogenated polymers usually have high highest occupied molecular orbital (HOMO) energy levels and inferior self-aggregation properties in solution, thus resulting in low power conversion efficiencies (PCEs). Herein, two nonhalogenated polymers, PB1 and PB2, are prepared.

A Sulfhydryl Azobenzene-Modified Polyaniline/Silver Electrode and Its Photoswitching Electrochemical Performance.

In this work, a sulfhydryl-functionalized azobenzene derivative (Azo) was synthesized and polyaniline/silver was modified (PANI/Ag) to make a nanocomposite (PANI/Ag/Azo). A series of characterization techniques likeHNMR, UV-vis absorption spectra, Raman spectra, FT-IR, XRD, SEM, TEM, and TGA was employed to study Azo, PANI/Ag, and PANI/Ag/Azo. Electrochemical properties were measured by cyclic voltammetry (CV) and galvanostatic charging/discharging (GCD).

Organic photovoltaic cell with 17% efficiency and superior processability.

The development of organic photoactive materials, especially the newly emerging non-fullerene electron acceptors (NFAs), has enabled rapid progress in organic photovoltaic (OPV) cells in recent years. Although the power conversion efficiencies (PCEs) of the top-performance OPV cells have surpassed 16%, the devices are usually fabricated via a spin-coating method and are not suitable for large-area production. Here, we demonstrate that the fine-modification of the flexible side chains of NFAs can yield 17% PCE for OPV cells.

Reduced Nonradiative Recombination Energy Loss Enabled Efficient Polymer Solar Cells via Tuning Alkyl Chain Positions on Pendent Benzene Units of Polymers.

Nonradiative recombination energy loss (Δ) plays a key role in enhancing device efficiencies for polymer solar cells (PSCs). Until now, there is no clear resolution for reducing Δ via molecular design. Herein, we report two conjugated polymers, PBDB-P- and PBDB-P-, which are integrated from benzo[1,2-:4,5-']dithiophene with alkylthio chain substituted at para- or meta-position on pendent benzene and benzo[1,2-:4,5-']dithiophene-4,8-dione.

Recent progress in wide bandgap conjugated polymer donors for high-performance nonfullerene organic photovoltaics.

In the last five years, the tremendous progress achieved in the field of polymer solar cells (PSCs) has attracted extensive attention to this emerging technology for exploiting renewable energy. Owing to their excellent optoelectronic features and outstanding manufacturability for film deposition, wide bandgap (WBG) polymer donors have become a leading component in bulk heterojunction layers and thus, a correlative review focusing on their molecular design, aggregation behavior and photovoltaic properties is necessary. In this feature article, we summarize our recent efforts in developing WBG polymer donors and understanding the charge separation and non-radiative recombination energy loss in high-performance non-fullerene (NF) PSCs.

Single-Junction Organic Photovoltaic Cells with Approaching 18% Efficiency.

Optimizing the molecular structures of organic photovoltaic (OPV) materials is one of the most effective methods to boost power conversion efficiencies (PCEs). For an excellent molecular system with a certain conjugated skeleton, fine tuning the alky chains is of considerable significance to fully explore its photovoltaic potential. In this work, the optimization of alkyl chains is performed on a chlorinated nonfullerene acceptor (NFA) named BTP-4Cl-BO (a Y6 derivative) and very impressive photovoltaic parameters in OPV cells are obtained.

Tailoring and Modifying an Organic Electron Acceptor toward the Cathode Interlayer for Highly Efficient Organic Solar Cells.

With the rapid advance of organic photovoltaic materials, the energy level structure, active layer morphology, and fabrication procedure of organic solar cells (OSCs) are changed significantly. Thus, the photoelectronic properties of many traditional electrode interlayers have become unsuitable for modifying new active layers; this limits the further enhancement in OSC efficiencies. Herein, a new design strategy of tailoring the end-capping unit, ITIC, to develop a cathode interlayer (CIL) material for achieving high power conversion efficiency (PCE) in OSCs is demonstrated.

A Carbonylated Terthiophene-Based Twisted Polymer for Efficient Ternary Polymer Solar Cells.

In polymer solar cells (PSCs), it is difficult for twisted conjugated polymers to achieve high power-conversion efficiency (PCE) as donors due to their low charge carrier mobilities and poor bulk heterojunction morphologies. In this work, a new twisted conjugated polymer (P3TCO-1) with excellent solubilities (above 30 mg mL ) in common organic solvents at room temperature is reported. UV-visible absorption spectra and cyclic voltammetry indicate that P3TCO-1 has a wide optical bandgap of 1.

Three-Dimensional Pyrene-Fused N-Heteroacenes.

Four three-dimensional (3D) pyrene-fused N-heteroacenes (P1-P4) are designed and synthesized. From P1 to P4, their lengths are extended in an iterative way, where the thiadiazole unit can be reduced to diamine and the obtained diamines can be further condensed with the diketones with a thiadiazole unit. Compared to their two-dimensional counterparts, the solubility of these 3D pyrene-fused N-heteroacenes is improved by this 3D covalent linkage with two-dimensional units.

Asymmetric Wide-Bandgap Polymers Simultaneously Improve the Open-Circuit Voltage and Short-Circuit Current for Organic Photovoltaics.

A trade-off between open-circuit voltage (V ) and high short-circuit (J ) becomes one of the most vital problems limiting further improvement in polymer solar cells' (PSCs) efficiency. In this work, two asymmetric polymer donors PBDT-F-2TC and PBDT-SF-2TC are designed and synthesized. When blended with a state-of-the-art acceptor IT-4F with low lowest-unoccupied molecular orbital level, simultaneously high V (up to 0.