Volatile Imide Additives with Large Dipole and Special Film Formation Kinetics Enable High-Performance Organic Solar Cells.

Large dipole moment additives have strong interactions with the host materials, which can optimize morphology and improve the photovoltaic performance of organic solar cells (OSCs). However, these additives are difficult to remove due to their strong intermolecular interactions, which may impair stability. Developing volatile additives with large dipole moments is challenging.

Small Singlet-Triplet Gap Terpolymer Donor with a Simple Pt Complex Enables Organic Solar Cells with Low Energy Loss and Over 19.2% Efficiency.

Suppressing the non-radiative loss in the organic solar cells (OSCs) through molecular design remains a significant challenge. Typically, triplet state of organic semiconductors is lower than the charge transfer (CT) state, contributing to substantial non-radiative loss via the triplet state. Herein, a set of terpolymers is prepared by introducing a simple Pt complex block into the PM6 polymer backbone.

Rhodanine Substitution of Asymmetric Nonfullerene Acceptors for High-Performance Organic Solar Cells.

Asymmetric substitution is acknowledged as a straightforward yet potent approach for the optimization of small molecule acceptors (SMAs), thereby enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs). In this work, we have successfully engineered and synthesized a novel asymmetric SMA, designated as Y6-R, which features a rhodanine-terminated inner side-chain. In devices with PM6 as the polymer donor, the asymmetric Y6-R demonstrated an impressive PCE of 18.

Modulation of Molecular Quadrupole Moments by Phenyl Side-Chain Fluorination for High-Voltage and High-Performance Organic Solar Cells.

The ground-state charge generation (GSCG) in photoactive layers determines whether the photogenerated carriers occupy the deep trap energy levels, which, in turn, affects the device performance of organic solar cells (OSCs). In this work, charge-quadrupole electrostatic interactions are modulated to achieve GSCG through a molecular strategy of introducing different numbers of F atom substitutions on the BTA3 side chain. The results show that 8F substitution (BTA3-8F) and 16F substitution (BTA3-16F) lead to different patterns of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy level changes.

A perspective on field-effect in energy and environmental catalysis.

The development of catalytic technologies for sustainable energy conversion is a critical step toward addressing fossil fuel depletion and associated environmental challenges. High-efficiency catalysts are fundamental to advancing these technologies. Recently, field-effect facilitated catalytic processes have emerged as a promising approach in energy and environmental applications, including water splitting, CO reduction, nitrogen reduction, organic electrosynthesis, and biomass recycling.

Upper Layer-Modulated Pseudo Planar Heterojunction with Metal Complex Acceptor for Efficient and Stable Organic Photovoltaics.

Modulating self-aggregation and charge transport in the upper acceptor layer of the pseudo planar heterojunction (PPHJ) is crucial for enhancing dielectric constant and suppressing trap density, leading to efficient and stable organic photovoltaics (OPVs). In this work, a metal complex acceptor (MCA), PtAC-Cl, is selectively incorporated into the upper host Y6 layer of PPHJ to regulate morphology and fill trap states. There exists a strong chemical interaction between PtAC-Cl and Y6, which can promote electron transfer.

Surface Regulation via Carboxylate Polymer for Efficient and Stable CsPbIBr Perovskite Solar Cells.

CsPbIBr perovskite solar cell (PSC) is a promising candidate for high-efficiency single-junction and tandem solar cells. However, due to the numerous surface defects of the CsPbIBr film and the mismatch of energy levels at the CsPbIBr/charge transport layer interface, the power conversion efficiency (PCE) of CsPbIBr PSC is still significantly lower than the theoretical limits. To alleviate those issues, in this work, a carboxylate-based p-type polymer, TTC-Cl, is employed to modify the surface of CsPbIBr layer.

Polymer Based on Asymmetrically Halogenated Benzotriazole Enables High Performance Organic Solar Cells Prepared in Nonhalogenated Solvent.

Halogenation on the A unit of the D-π-A-type polymer donor has been proven as an effective strategy to improve the performance of organic solar cells (OSCs). Compared with fluorination, chlorination usually increases the open-circuit voltage because of the downward shift of energy levels, but decreases the charge transport ability due to the large steric hindrance of the chlorine atom. We reported herein a method to balance the energy loss and charge transport through asymmetric halogenation on the benzotriazole (BTA) unit of the polymer.

Selenophene-fused Perylene Diimide-Based Cathode Interlayer Enables 19 % Efficiency Binary Organic Solar Cells via Stimulative Charge Extraction.

The cathode interlayer is crucial for the development of organic solar cells (OSCs), but the research on simple and efficient interlayer materials is lagging behind. Here, a donor-acceptor (D-A) typed selenophene-fused perylene diimide (PDI) derivative (SePDI3) is developed as cathode interlayer material (CIM) for OSCs, and a non-fused PDI derivative (PDI3) is used as the control CIM for comparison. Compared to PDI3, SePDI3 shows a stronger self-doping effect and better crystallinity, resulting in better charge transport ability.

The Development of Quinoxaline-Based Electron Acceptors for High Performance Organic Solar Cells.

In the recent advances of organic solar cells (OSCs), quinoxaline (Qx)-based nonfullerene acceptors (QxNFAs) have attracted lots of attention and enabled the recorded power conversion efficiency approaching 20%. As an excellent electron-withdrawing unit, Qx possesses advantages of many modifiable sites, wide absorption range, low reorganization energy, and so on. To develop promising QxNFAs to further enhance the photovoltaic performance of OSCs, it is necessary to systematically summarize the QxNFAs reported so far.

Control of Multi-Fluorination Number and Position in D-π-A Type Polymers and Their Impact on High-Voltage Organic Photovoltaics.

Exploring the structure-performance relationship of high-voltage organic solar cells (OSCs) is significant for pushing material design and promoting photovoltaic performance. Herein, we chose a D-π-A type polymer composed of 4,8-bis(thiophene-2-yl)-benzo[1,2-:4,5-']dithiophene (BDT-T) and benzotriazole (BTA) units as the benchmark to investigate the effect of the fluorination number and position of the polymers on the device performance of the high-voltage OSCs, with a benzotriazole-based small molecule (BTA3) as the acceptor. , , and are the polymers with progressively increasing F atoms on the D units, while , , and are the polymers with further attachment of F atoms to the BTA units based on the above three polymers.

Tethered Helical Ladder-Type Aromatic Lactams.

Tethered nonplanar aromatics (TNAs) make up an important class of nonplanar aromatic compounds showing unique features. However, the knowledge on the synthesis, structures, and properties of TNAs remains insufficient. In this work, a new type of TNAs, the tethered aromatic lactams, is synthesized via Pd-catalyzed consecutive intramolecular direct arylations.

Optimizing Molecular Crystallinity and Suppressing Electron-Phonon Coupling in Completely Non-Fused Ring Electron Acceptors for Organic Solar Cells.

High open-circuit voltage (V) organic solar cells (OSCs) have received increasing attention because of their promising application in tandem devices and indoor photovoltaics. However, the lack of a precise correlation between molecular structure and stacking behaviors of wide band gap electron acceptors has greatly limited its development. Here, we adopted an asymmetric halogenation strategy (AHS) and synthesized two completely non-fused ring electron acceptors (NFREAs), HF-BTA33 and HCl-BTA33.

Room Temperature Ionic Liquid Capping Layer for High Efficiency FAPbI Perovskite Solar Cells with Long-Term Stability.

Ionic liquid salts (ILs) are generally recognized as additives in perovskite precursor solutions to enhance the efficiency and stability of solar cells. However, the success of ILs incorporation as additives is highly dependent on the precursor formulation and perovskite crystallization process, posing challenges for industrial-scale implementation. In this study, a room-temperature spin-coated IL, n-butylamine acetate (BAAc), is identified as an ideal passivation agent for formamidinium lead iodide (FAPbI) films.

Dithienoquinoxalineimide-Based Polymer Donor Enables All-Polymer Solar Cells Over 19 % Efficiency.

All-polymer solar cells (all-PSCs) have been regarded as one of the most promising candidates for commercial applications owing to their outstanding advantages such as mechanical flexibility, light weight and stable film morphology. However, compared to large amount of new-emerging excellent polymer acceptors, the development of high-performance polymer donor lags behind. Herein, a new D-π-A type polymer donor, namely QQ1, was developed based on dithienoquinoxalineimide (DTQI) as the A unit, benzodithiophene with thiophene-conjugated side chains (BDTT) as the D unit, and alkyl-thiophene as the π-bridge, respectively.

Noncovalent Interaction Boosts Performance and Stability of Organic Solar Cells Based on Giant-Molecule Acceptors.

Designing giant-molecule acceptors is deemed as an up-and-coming strategy to construct stable organic solar cells (OSCs) with high performance. Herein, two giant dimeric acceptors, namely, DYV and DYFV, have been designed and synthesized by linking two Y-series derivatives with a vinyl unit. DYFV exhibits more red-shifted absorption, down-shifted energy levels, and enhanced intermolecular packing than DYV because the intramolecular noncovalent interaction (H···F) of DYFV leads to better coplanarity of the backbone.

Effect of Number and Position of Chlorine Atoms on the Photovoltaic Performance of Asymmetric Nonfullerene Acceptors.

It has been well proved that the introduction of halogen can effectively modify the optoelectronic properties of classic symmetric nonfullerene acceptors (NFAs). However, the relevant studies for asymmetric NFAs are limited, especially the effect of halogen substitution number and position on the photovoltaic performance is not clear. In this work, four asymmetric NFAs with A-D-A-A structure are developed by tuning the number and position of chlorine atoms on the 1,1-dicyanomethylene-3-indanone end groups, namely, A303, A304, A305, and A306.

A-A-D-A-A-Type Nonfullerene Acceptors.

The A-A-D-A-A-type molecules consist of one electron-donating (D) core flanked by two electron-accepting units (A and A) and have emerged as an essential branch of nonfullerene acceptors (NFAs). These molecules generally possess higher molecular energy levels and wider optical bandgaps compared with those of the classic A-D-A- and A-DA'D-A-type NFAs, owing to the attenuated intramolecular charge transfer effect. These characteristics make them compelling choices for the fabrication of high-voltage organic photovoltaics (OPVs), ternary OPVs, and indoor OPVs.

Benzotriazole-Based 3D Four-Arm Small Molecules Enable 19.1 % Efficiency for PM6 : Y6-Based Ternary Organic Solar Cells.

A third component featuring a planar backbone structure similar to the binary host molecule has been the preferred ingredient for improving the photovoltaic performance of ternary organic solar cells (OSCs). In this work, we explored a new avenue that introduces 3D-structured molecules as guest acceptors. Spirobifluorene (SF) is chosen as the core to combine with three different terminal-modified (rhodanine, thiazolidinedione, and dicyano-substituted rhodanine) benzotriazole (BTA) units, affording three four-arm molecules, SF-BTA1, SF-BTA2, and SF-BTA3, respectively.

Recent Advances in Organic Photovoltaic Materials Based on Thiazole-Containing Heterocycles.

Organic solar cells (OSCs) have achieved great progress, driven by the rapid development of wide bandgap electron donors and narrow bandgap non-fullerene acceptors (NFAs). Among a large number of electron-accepting (A) building blocks, thiazole (Tz) and its derived fused heterocycles have been widely used to construct photovoltaic materials, especially conjugated polymers. Benefiting from the electron deficiency, rigidity, high planarity, and enhanced intra/intermolecular interactions of Tz-containing heterocycles, some related photovoltaic materials exhibit proper energy levels, optimized molecular aggregation, and active layer morphology, leading to excellent photovoltaic performance.

Dithienobenzothiadiazole (DTBT)-Based Polymers Enable Organic Solar Cells with Ultrahigh V of ≈1.3 V.

Dithieno[3',2':3,4;2",3":5,6]benzo[1,2-c][1,2,5]thiadiazole (DTBT) is a newly emerging building block to construct effective photovoltaic polymers. Organic solar cells (OSCs) based on DTBT-based polymers have realized power conversion efficiency (PCEs) over 18%, despite their relatively low open-circuit voltage (V ) of 0.8-0.

Modulation of Molecular Stacking via Tuning 2-Ethylhexyl Alkyl Chain Enables Improved Efficiency for All-Small-Molecule Organic Solar Cells.

There is always a dilemma between strong π-π stacking/crystallinity and suitable domain size for all-small-molecule organic solar cells (ASM-OSCs), which puts forward higher requirements for the design of molecular donors. In this work, a series of novel molecular donors with different positional 2-ethylhexy (EH) attachments are designed and synthesized, named SM-R, SM-REH, SM-EH-R, and SM-EH-REH. It is found that EH-substitution on end groups (SM-REH) enables improved π-π interaction and crystallinity but with decreased solubility and phase size, leading to the improved efficiency of 15.

Constructing D-π-A Type Polymers as Dopant-Free Hole Transport Materials for High-Performance CsPbIBr Perovskite Solar Cells.

Hole-transporting materials (HTMs) play a major role in efficient and stable perovskite solar cells (PSCs), especially for CsPbIBr inorganic PSC. Among them, dopant-free conjugated polymers attract more attention because of the advantages of high hole mobility and high stability. However, the relationship between the polymer structure and the photovoltaic performance is rarely investigated.