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The introduction of solvent additives has become a general approach in optimizing the active layer morphology in organic photovoltaics (OPV) to achieve high power conversion efficiency. It is of general interest to understand the mechanism of how additives optimize the thin-film nanostructure formation such as crystallization kinetics and phase separation. In the current manuscript, state-of-the-art nonfullerene bulk heterojunction blends, PM6:IT-4F mixture, are used in a slot-die coating experiment. The 1,8-octanedithiol (DIO)-aided fabrication leads to a significant increase in the power conversion efficiency (PCE) from 10.11 to 12.67%. Exciton dissociation and carrier transport have also been improved, largely associated with morphology improvement. Time-resolved crystallization kinetics during PM6:IT-4F film formation under different processing conditions was studied by in situ grazing-incidence wide-angle X-ray scattering (GIWAXS), in which a detailed polymer fibril morphology formation was seen. The Johnson–Mehl–Avrami–Kolmogorov (JMAK) crystallization analysis affords insights that the addition of the DIO additive in a small amount would not only increase the nucleation rate during the nucleation and growth stage but also introduce secondary fibril crystal perfection via burst nucleation-mediated crystallization to a grain boundary-induced crystallization stage change. These observations can be of general interest to the OPV community in manipulating the printed solar cell morphology and efficiency toward the commercial application.

Non-fullerene acceptor (NFA) based organic solar cells (OSCs) are of high efficiency and low energy loss and low recombination features, which is owing to the advantage of non-fullerene acceptors. The photophysics investigation of non-fullerene solar cells, in comparing to fullerene based analogue as well as mixed acceptor ternary blends could help to understand the working mechanism of NFA functioning mechanism. We choose PBDB-T donor, the fullerene derivative PC71BM acceptor, and the non-fullerene acceptor ITIC as the model system, to construct binary and ternary solar cells, which then subject to ultrafast spectroscopy investigation. The charge transfer pathway in binary and ternary blends is revealed. And it is seen that ITIC leads to a faster exciton separation and exciton diffusion. ITIC in blends suppresses the geminate recombination and shows smaller amount of charge transfer states, which is beneficial for the device performance. And the addition of ITIC enhances the crystallinity for both donor and acceptor leads to a morphology change of forming bicontinuous crystalline networks and phase separation. In a consequence, fill factor and JSC, increase dramatically for the related OSC.

Polymeric dopant strategy distinctly suppressed the molecular aggregations and surface dewetting of the NPB small molecule hole transport layer in perovskite photovoltaics.

The active layer morphology transition of organic photovoltaics under non-equilibrium conditions are of vital importance in determining the device power conversion efficiency and stability; however, a general and unified picture on this issue has not been well addressed. Using combined in situ and ex situ morphology characterizations, morphological parameters relating to kinetics and thermodynamics of morphology evolution are extracted and studied in model systems under thermal annealing. The coupling and competition of crystallization and demixing are found to be critical in morphology evolution, phase purification and interfacial orientation. A unified model summarizing different phase diagrams and all possible kinetic routes is proposed. The current observations address the fundamental issues underlying the formation of the complex multi-length scale morphology in bulk heterojunction blends and provide useful morphology optimization guidelines for processing devices with higher efficiency and stability., Designing efficient blue perovskite LEDs by using mixed halides perovskite is still a challenge, limited mainly by the phase segregation issue. Here, the authors demonstrate in situ fabrication of quasi-2D CsPbClBr2 nanocrystal films with mixed ligands to overcome the constraint.

The chemical structure of donors and acceptors limit the power conversion efficiencies achievable with active layers of binary donor-acceptor mixtures. Here, using quaternary blends, double cascading energy level alignment in bulk heterojunction organic photovoltaic active layers are realized, enabling efficient carrier splitting and transport. Numerous avenues to optimize light absorption, carrier transport, and charge-transfer state energy levels are opened by the chemical constitution of the components. Record-breaking PCEs of 18.07% are achieved where, by electronic structure and morphology optimization, simultaneous improvements of the open-circuit voltage, short-circuit current and fill factor occur. The donor and acceptor chemical structures afford control over electronic structure and charge-transfer state energy levels, enabling manipulation of hole-transfer rates, carrier transport, and non-radiative recombination losses., Efficiency of organic solar cells is determined by the physical properties of donors and acceptors in bulk heterojunction film. The authors optimise quaternary blends to realize a double cascading energy level alignment enabling efficient carrier dissociation and transport, achieving 18% efficiency.

The chemical structure of donors (Ds) and acceptors (As) limit the power conversion efficiencies (PCEs) achievable with bulk heterojunction (BHJ) active layers of binary D-A mixtures. However, using quaternary D-A blends, double cascading energy level alignment in BHJ organic photovoltaic active layers are realized, enabling efficient carrier splitting and transport. Numerous avenues to optimize light absorption, carrier transport, and charge transfer state energy levels are opened by the chemical constitution of the components. Record-breaking PCEs of 18.07% are achieved where, by electronic structure and morphology optimization, simultaneous improvements of the open-circuit voltage, short-circuit current and fill factor occur. The D and A chemical structures afford control over electronic structure and charge transfer state energy levels, enabling manipulation of hole-transfer rates, carrier transport, and non-radiative recombination losses.

A new tellurate compound Na4CuTeO6 was synthesized by a conventional high-temperature solid state reaction. The titled compound crystallizes in the monoclinic system of a space group C2/c and exhibits a unique spin-chain structure built by planar CuO4 squares and TeO6 octahedra along the [101] direction. Magnetic measurements confirm that Na4CuTeO6 possesses an antiferromagnetic ordering at TN = ∼2.5 K. The intrachain and interchain interactions are estimated by a spin-chain model, showing a less pronounced 1D character in the system.

Novel mixed-anionic-group compounds M 2 (SeO 3 )(Te 3 O 7 ) (M = Co 2+ , Ni 2+ ) are successfully synthesized by a conventional hydrothermal method. Two compounds are isostructural which crystallize in the orthorhombic system of a space group Pnma . The framework shows a (MO 6 ) ∞ chain structure along the b -axis, while SeO 3 groups are isolated and Te 3 O 7 groups form the (Te 3 O 7 ) ∞ chains running along the a -axis. This is the first time to realize transition-metal compounds coexisting with Se 4+ and Te 4+ anionic groups. Magnetic measurements show that Co 2 (SeO 3 )(Te 3 O 7 ) possesses an antiferromagnetic ordering at ∼11 K, while Ni 2 (SeO 3 )(Te 3 O 7 ) exhibits a similar antiferromagnetic ordering at ∼31 K. Also, the fitting of magnetic susceptibility using a spin-chain model gives the exchange coupling J /k B = −1.515 K for Co 2 (SeO 3 )(Te 3 O 7 ) and J /k B = −8.963 K for Ni 2 (SeO 3 )(Te 3 O 7 ), respectively.

Mixtures of nonfullerene acceptors (NFAs) are prepared to fine‐tune bulk heterojunction (BHJ) thin‐film morphologies. The acceptor phase resulting from these mixtures has unique physical properties with excellent optoelectronic processes that dictate the output of organic photovoltaic (OPV) devices. Remarkable short‐circuit current densities (JSC) and fill factors (FFs) are achieved due to the formation of better crystalline fibrils that suppress geminate recombination, leading to improved charge transport with enhanced crystallinity and aligned cascading energy levels confirm efficient exciton diffusion and dissociation, yielding more effective exciton recycling. The decreased Urbach energy and suppressed energetic disorder account for the improvement in the open‐circuit voltage (VOC). A maximum power conversion efficiency of 17.86% is obtained, underscoring the importance of using specific material interactions to produce a suitable morphology and manage energy loss, resulting in ideal organic solar cell (OSC) devices.

Cs 2 NaMn 3 F 12 , one of manganese based fluorides A 2 A′Mn 3 F 12 (A = Rb, Cs; A′ = Li, Na, K), has been found to exhibit a typical kagome structure. Here, we report the first successful growth of large-sized single crystals of Cs 2 NaMn 3 F 12 by means of a hydrothermal method. Good quality of grown crystals is confirmed by the XRD and EDS techniques. Magnetic measurements suggest that Cs 2 NaMn 3 F 12 possesses an antiferromagnetic ordering at 2.5 K and a remarkably geometrical frustration effect in the system.

Two new compounds Sr2Cu5(PO4)4X2·8H2O (X = Cl and Br) are synthesized by a conventional hydrothermal method. Sr2Cu5(PO4)4Cl2·8H2O crystallizes in the tetragonal system with a space group of P4212, while Sr2Cu5(PO4)4Br2·8H2O crystallizes in the space group P4/nmm, which are found to have a similar framework of layered structure, in which the crown-like {Cu5(PO4)4X2} building units connect to each other forming a 2D corrugated sheet with vacancies, while the Sr2+ cations are located along the vacancies. The spin lattice of two compounds built by Cu2+ ions shows a new type of corrugated square. Magnetic measurements confirmed that both Sr2Cu5(PO4)4X2·8H2O (X = Cl and Br) exhibit antiferromagnetic ordering at low temperatures. A fit of theoretical model shows exchange interaction J = −25.62 K for the Cl-analogue and J/kB = −26.47 K for the Br-analogue.

Two fluorophosphates, BaMPO4F (M = Cu, Co), have been synthesized by a conventional hydrothermal method, and they crystallize in the orthorhombic system with the space group P212121, exhibiting a tunnel structure built by distorted MO4F square-pyramids and PO4 tetrahedra. The magnetic behaviors of the two compounds are investigated by means of magnetic susceptibility, magnetization, and heat capacity measurements. The results indicate that BaCuPO4F exhibits a paramagnetic behavior down to 2 K, while BaCoPO4F undergoes long-range antiferromagnetic ordering at 11.3 K and short-range magnetic ordering at ∼22 K.

All-polymer solar cells (all-PSCs) exhibit excellent stability and readily tunable ink viscosity, and are therefore especially suitable for printing preparation of large-scale devices. At present, the efficiency of state-of-the-art all-PSCs fabricated by the spin-coating method has exceeded 11%, laying the foundation for the preparation and practical utilization of printed devices. A high power conversion efficiency (PCE) of 11.76% is achieved based on PTzBI-Si:N2200 all-PSCs processing with 2-methyltetrahydrofuran (MTHF, an environmentally friendly solvent) and preparation of active layers by slot die printing, which is the top efficient for all-PSCs. Conversely, the PCE of devices processed by high-boiling point chlorobenzene is less than 2%. Through the study of film formation kinetics, volatile solvents can freeze the morphology in a short time, and a more rigid conformation with strong intermolecular interaction combined with the solubility limit of PTzBI-Si and N2200 in MTHF results in the formation of a fibril network in the bulk heterojunction. The multilength scaled morphology ensures fast transfer of carriers and facilitates exciton separation, which boosts carrier mobility and current density, thus improving the device performance. These results are of great significance for large-scale printing fabrication of high-efficiency all-PSCs in the future.

The intrinsic electronic properties of donor (D) and acceptor (A) materials in coupling with morphological features dictate the output in organic solar cells (OSCs). New physical properties of intimate eutectic mixing are used in nonfullerene-acceptor-based D-A1 -A2 ternary blends to fine-tune the bulk heterojunction thin film morphology as well as their electronic properties. With enhanced thin film crystallinity and improved carrier transport, a significant JSC amplification is achieved due to the formation of eutectic fibrillar lamellae and reduced defects state density. Material wise, aligned cascading energy levels with much larger driving force, and suppressed recombination channels confirm efficient charge transfer and transport, enabling an improved power conversion efficiency (PCE) of 17.84%. These results reveal the importance of utilizing specific material interactions to control the crystalline habit in blended films to form a well-suited morphology in guiding superior performances, which is of high demand in the next episode of OSC fabrication toward 20% PCE.

Recently, small molecule hole transporting layers (HTLs) have attracted growing interest in perovskite solar cells due to their low-cost, excellent stability, and better energy level alignment with the perovskites. Nonetheless, an amorphous and coarse surface film is one of the main obstructions to the performance of these small molecule HTLs. Herein, a small molecule, namely, N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) was doped with a polymer to overcome the formation of molecular aggregation in an HTL. This polymer doping strategy resulted in a very smooth surface, which improved the photo-physical and electrochemical properties at the HTL/perovskite interface. Consequently, a maximum power conversion efficiency (PCE) of 17.80%, 32% higher than that of the control, i.e., the NPB-based device (13.57%), has been achieved. This study reveals the critical influence of molecular aggregations on the performance of perovskite solar cells, which impairs the development of an efficient device based on small molecule HTLs.

Two fluorophosphates, BaMPO

Two new compounds Sr

The family of Archimedean lattices has eleven numbers, yet several of these lattices have not been reported for transition metal oxides. Here, the last number of Archimedean lattice was firstly realized in a layered phosphate.