Optimizing Photovoltaic Performance through Functional End-Capping Units of Polymer Donor Materials.

Advancing the photovoltaic performances of organic solar cells (OSCs) is vital for commercialization. High-performance OSC active layers commonly comprise polymer donors and small molecule acceptors. Enhanced crystallinity, ordered molecular packing, and strong intermolecular interactions in polymer donors can improve carrier mobility and photovoltaic performance.

3D-Architectured Acceptor with High Photoluminescence Quantum Yield and Moderate Crystallinity for High-efficiency Organic Solar Cells with Low Voltage Loss.

This study outlines a molecular design approach that entails integrating 3D structural motifs into the central core or terminal groups of fused-ring acceptor molecules, specifically, LLZ1, LLZ2, and LLZ3-by incorporating a 3D architecture unit of norbornene. The objective is to modulate the aggregation behavior of these molecules by modifying their molecular structure, thereby enhancing the photoluminescence quantum yield (PLQY) values of the acceptor materials and reducing the non-radiative recombination voltage loss in the corresponding devices. Our research findings demonstrate that the introduction of norbornene units effectively suppresses excessive molecular aggregation and significantly improves the PLQY values of the acceptor molecules.

Fabricating High-Performance Organic Solar Cells by Using Inside-Chain Chlorinated Acceptor as a Ternary Component.

In this study, two molecules, WLA1 and WLA2, with the same molecular backbone but with different degrees of inside-chain chlorination, are designed and synthesized to elucidate the effects of chlorine substitution strategies on the morphology of small-molecule acceptors and blended films. The chlorinated WLA2 enhances crystallinity and molecular stacking. For binary organic solar cells (OSCs), the corresponding blended films of WLA2 exhibit suitable phase separation and crystallinity.

Facile Synthesis of High-Entropy Alloy Nanoparticles Comprising of Dissimilar Elements.

High-entropy alloy nanoparticles (HEA-NPs) have developed as desirable functional material. Methods including the direct solution synthesis have been reported, and it has demonstrated success in fabricating HEA-NPs. Nevertheless, its applicability to systems containing dissimilar elements remains constrained by phase segregation and incomplete alloying.

Amphiphilic Photosensitizer Based on Benzothioxanthene: Exploring Aggregation-Induced Enhancement of Reactive Oxygen Species Generation.

The application of photosensitizers has long been hindered by complex synthesis routes and poor water solubility. In this study, we report novel benzothioxene-based photosensitizers with significant improvements in both solubility and photodynamic efficiency. Among them, the amphiphilic molecule QA-BTXI stands out, offering exceptional water solubility and pronounced aggregation-induced enhancement of reactive oxygen species generation.

Application of n-Type or p-Type Dopants in Organic Photovoltaics.

Compared to inorganic semiconductors, organic semiconductors (OSCs) exhibit lower permittivity and carrier mobility. This is primarily attributed to their weaker van der Waals forces and the significant structural and energetic disorder, ultimately impeding the commercial application of organic photovoltaics (OPVs). However, the introduction of n-type or p-type dopants offers a solution.

Amide-Based Cathode Interfacial Layer with Dual-Modification Mechanisms Enables Stable Organic Solar Cells with High Efficiency Achieving 20.

The cathode interfacial layers (CILs) play a critical role in the performance and long-term stability of the organic solar cells (OSCs). While amine-based CILs have been successful in reducing the work function of metal electrodes, they can also promote the decomposition of acceptor materials, compromising the stability of OSCs. To address this challenge and further improve device performance, we have innovatively designed and synthesized amide-functionalized perylene diimide (PDI)-Leu-am as a dopant-free CIL molecule.

Naphthalene Diimide-Embedded Donor-Acceptor Carbon Nanohoops: Photophysical, Photoconductive, and Charge Transport Properties.

Designing the architecture of donor-acceptor (D-A) pairs is an effective strategy to tailor the electronic structure of conjugated macrocycles for optoelectronic devices. Herein, we present the synthesis of three D-A nanohoops ( = 7, 8, 9) containing a naphthalene diimide (NDI) unit as an acceptor and []cycloparaphenylenes ([]CPPs) moieties as donors. The D-A characteristics of were substantiated through absorption and fluorescence spectroscopic studies, electrochemical investigations, and computational analysis.

Reducing Non-Radiative Energy Losses in Non-Fullerene Organic Solar Cells.

With the rapid advancement of non-fullerene acceptors (NFAs), the power conversion efficiency (PCE) of organic solar cells (OSCs) has surpassed the 20 % threshold, highlighting their considerable potential as next-generation energy conversion devices. In comparison to inorganic or perovskite solar cells, the open-circuit voltage (V) of OSCs is constrained by substantial non-radiative energy losses (ΔE), leading to values notably below those anticipated by the Shockley-Queisser limit. In OSCs, non-radiative energy losses are intimately associated with the electroluminescent quantum efficiency (EQE) of charge transfer states, which is in turn directly affected by the photoluminescence quantum yield (PLQY) of acceptor materials.

Constructing efficient organic solar cells by highly volatile solid additives with controlled phase morphology.

We synthesized two highly volatile and low-cost solid additives, PT and TFT. The inclusion of PT and TFT effectively influences the aggregation behavior of D18: L8-BO during the film-forming process. Consequently, PT and TFT-treated D18: L8-BO-based OSCs achieved power conversion efficiencies of 18.

All Roads Lead to Rome: Isomers with Divergent Cathode Modification Mechanisms toward Ohmic Contact.

Cathode interfacial layers (CILs) hold utmost importance for achieving ohmic contact at the organic semiconductor-cathode interface of organic photovoltaic devices. Delving deep into diverse design principles and working mechanisms is of great significance for designing novel CILs with high performance. Herein, two novel nonamine-based CILs are designed: one featuring a cyclopentadiene unit, designated as CIL-cp; while the other, lacking cyclopentadiene, is referred to as CIL-ph, which is an isomer of CIL-cp.

The efficient triplet states formation of Se-modified PDI dimers and tetramers in solvents.

The triplet excited states of molecules play an important role in photophysical processes, which has attracted great research interest. Perylene diimide (PDI) is a widely studied material closely associated with the generation of triplet states, and it is highly anticipated to become an electron acceptor material for improving photovoltaic conversion efficiency. In this work, we prepared dimers and tetramers composed of selenium-modified PDI-C5 ('-bis(6-undecyl) perylene-3,4,9,10-bis(dicarboximide)) units.

Boosting organic solar cell efficiency tailored end-group modifications of novel non-fused ring electron acceptors.

In this study, we designed and synthesized two NFREAs, 2BTh-3F and 2BTh-CN, incorporating distinct substituents to modulate their electron-withdrawing properties. We meticulously explore the distinct impacts of these substituents on NFREA performance. Our investigation revealed that the introduction of 3,5-difluoro-4-cyanophenyl in 2BTh-CN significantly enhanced electron withdrawal and intramolecular charge transfer, leading to a red-shifted absorption spectrum and optimized energy levels.

Electron, hole, and energy transfer dynamics in non-fullerene small-molecule acceptors.

When photoexcited, an organic photovoltaic (OPV) donor/acceptor (D/A) blend is expected to undergo charge separation (CS) through three channels: electron transfer, hole transfer, and energy transfer-induced electron/hole transfer. However, previous spectroscopic studies on various blends based on non-fullerene acceptors (NFAs) have not been able to directly characterize the dynamics of these processes, due to spectral overlap of the involved intermediate species. Herein, we study the excited-state dynamics of D/A blends composed of PBDB-T (D) and a L-series NFA (L4 or L5) and show that the species responsible for these processes in the PBDB-T/L4 blend can be spectroscopically identified, allowing us to disentangle their dynamics.

Boosting the Efficiency of Perovskite/Organic Tandem Solar Cells via Enhanced Near-Infrared Absorption and Minimized Energy Losses.

The compatibility of perovskite and organic photovoltaic materials in solution processing provides a significant advantage in the fabrication of high-efficiency perovskite/organic tandem solar cells. However, additional recombination losses can occur during exciton dissociation in organic materials, leading to energy losses in the near-infrared region of tandem devices. Consequently, a ternary organic rear subcell is designed containing two narrow-bandgap non-fullerene acceptors to enhance the absorption of near-infrared light.

Boosting Organic Solar Cells to Over 18 % Efficiency through Dipole-Dipole Interactions in Fluorinated Nonfused Ring Electron Acceptors.

This study successfully designed and synthesized two nonfused ring electron acceptors, 412-6F and 412-6Cl, modified with fluorine and chlorine substituents, respectively. Single-crystal analysis revealed that 412-6F possesses a planar molecular backbone and exhibits pronounced dipole-dipole interactions between the fluorine atoms on the lateral phenyl groups and the carbonyl oxygen atoms on the end groups. This specific interaction promotes dense end-group stacking, leading to a reduced interlayer spacing.

Promotion of Fast and Efficient Singlet Fission Process of PDI Dimers by Selenium Substitution.

Singlet fission (SF) is a triplet generation mechanism capable of turning a singlet exciton into two triplet excitons. It has the potential to enhance the power conversion efficiency of single-junction solar cells. Perylene diimides (PDIs) are a class of dye molecules with photovoltaic properties and are beginning to receive more and more attention due to their potential for SF.

Hierarchical Solid-Additive Strategy for Achieving Layer-by-Layer Organic Solar Cells with Over 19 % Efficiency.

Layer-by-layer (LbL) deposition of active layers in organic solar cells (OSCs) offers immense potential for optimizing performance through precise tailoring of each layer. However, achieving high-performance LbL OSCs with distinct solid additives in each layer remains challenging. In this study, we explore a novel approach that strategically incorporates different solid additives into specific layers of LbL devices.

A 3,3'-Difluoro-2,2'-Bithiophene Based Donor Polymer Realizing High Efficiency (>17%) Single Junction Binary Organic Solar Cells.

In this study, two novel donor-acceptor (D-A) copolymers are designed and synthesized, DTBT-2T and DTBT-2T2F with 2,2'-bithiophene or 3,3'-difluoro-2,2'-bithiophene as the donor unit and dithienobenzothiadiazole as the acceptor unit, and used them as donor materials in non-fullerene organic solar cells (OSCs). Due to enhanced planarity of polymer chains resulted by the intramolecular F···S noncovalent interactions, the incorporation of 3,3'-difluoro-2,2'-bithiophene unit instead of 2,2'-bithiophene into the polymers can enhance their molecular packing, crystallinity and hole mobility. The DTBT-2T:L8-BO based binary OSCs deliver a power conversion efficiency (PCE) of only 9.

Sequentially Processed Bulk-Heterojunction-Buried Structure for Efficient Organic Solar Cells with 500 nm Thickness.

Large-area printing fabrication is a distinctive feature of organic solar cells (OSCs). However, the advance of upscalable fabrication is challenged by the thickness of organic active layers considering the importance of both exciton dissociation and charge collection. In this work, a bulk-heterojunction-buried (buried-BHJ) structure is introduced by sequential deposition to realize efficient exciton dissociation and charge collection, thereby contributing to efficient OSCs with 500 nm thick active layers.