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Extensive research on bulk‐heterojunction (BHJ) optimization has advanced organic photovoltaics (OPVs). However, the need for research addressing the issue of morphological instability and ensuring long‐term durability remains a priority. Herein, a diffusion‐governed morphological modification methodology via a sequential deposition (SD) process comprising ternary components with low miscibility is demonstrated. Sequential coating of a high glass transition temperature (Tg) material and a host binary blend induces a concentration difference between successively coated layers, allowing for effective blending of immiscible materials during solvent evaporation. The enhanced miscibility of the SD‐processed BHJ layer facilitates molecular interactions between the high Tg material and the host materials, thereby increasing the Tg of the BHJ blend. The SD‐processed OPVs exhibit superior photovoltaic performance and suppressed glass transition under thermal stress compared to reference OPVs fabricated via a conventional method. After 500 h of thermal aging at 85 °C, the SD‐BHJ OPV retains over 80% of its initial efficiency, whereas the reference device shows a drastic drop to below 80% of its initial efficiency after only 80 h. This study provides a step toward efficient, long‐term stable OPVs by overcoming the limitations of blend miscibility and poor thermal durability of conventional BHJ systems via a SD process. [ABSTRACT FROM AUTHOR]

Orbital anisotropy at interfaces in magnetic heterostructures has been key to pioneering spin–orbit‐related phenomena. However, modulating the interface's electronic structure to make it abnormally asymmetric has been challenging because of lack of appropriate methods. Here, the authors report that low‐energy proton irradiation achieves a strong level of inversion asymmetry and unusual strain at interfaces in [Co/Pd] superlattices through nondestructive, selective removal of oxygen from Co3O4/Pd superlattices during irradiation. Structural investigations corroborate that progressive reduction of Co3O4 into Co establishes pseudomorphic growth with sharp interfaces and atypically large tensile stress. The normal component of orbital to spin magnetic moment at the interface is the largest among those observed in layered Co systems, which is associated with giant orbital anisotropy theoretically confirmed, and resulting very large interfacial magnetic anisotropy is observed. All results attribute not only to giant orbital anisotropy but to enhanced interfacial spin–orbit coupling owing to the pseudomorphic nature at the interface. They are strongly supported by the observation of reversal of polarity of temperature‐dependent Anomalous Hall signal, a signature of Berry phase. This work suggests that establishing both giant orbital anisotropy and strong spin–orbit coupling at the interface is key to exploring spintronic devices with new functionalities. [ABSTRACT FROM AUTHOR]

To meet the requirements for indoor organic photovoltaic (OPV) applications, it is imperative to minimize charge recombination loss and enhance photovoltaic performance toward commercially compelling levels. Here, morphological modification in non‐fullerene blends is demonstrated to boost the efficiency and stability of indoor OPVs. For morphological modification, a ternary blend is devised by utilizing two well‐miscible non‐fullerene acceptors, which improve morphological features in the photoactive layer and suppress charge recombination loss. Morphological modification enhances OPV performance, particularly under low‐intensity indoor irradiation conditions, at which trap‐assisted recombination mainly governs the photovoltaic performance. The optimum ternary OPV shows a new record power conversion efficiency of 30.11% at a 500 lux light‐emitting diode, accompanied by excellent morphological durability under thermal stress, despite the use of "existing" photovoltaic materials designed for AM 1.5 G operation. This study elucidates the effects of morphology on OPV performance under low‐light conditions and suggests an ideal morphology for non‐fullerene OPVs with enhanced performance for indoor applications. [ABSTRACT FROM AUTHOR]

Interface engineering is critical for reducing trap states present in various device interfaces and improving the efficiency of perovskite solar cells (PSCs). This study introduces the blending effect of poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) into metal‐phthalocyanine−tetrasulfonated acid tetrasodium salt (TS‐MPc) used as a hole transport layer (HTL) in organic–inorganic hybrid PSCs. PEDOT:PSS with a low pH induces the self‐assembly and formation of mesh‐like nano‐networks in a TS‐MPc layer, which is confirmed by atomic force microscopy and elemental mapping using energy‐dispersive spectroscopy. Compared with pure TS‐MPc, nano‐networked TS‐MPc with PEDOT:PSS exhibits higher crystallinity by grazing‐incidence wide‐angle X‐ray scattering. The nano‐network formation contributes to ≈30% enhancement in the power conversion efficiency (14.65%) of device with PEDOT:PSS‐assisted TS‐CuPc as HTL, compared with device using conventional PEDOT:PSS (11.02%). In addition, the device with PEDOT:PSS‐assisted TS‐MPc shows a significant improvement in stability owing to the reduced pH of the HTL compared with the device using pristine PEDOT:PSS. [ABSTRACT FROM AUTHOR]

Herein the morphology and exciton/charge carrier dynamics in bulk heterojunctions (BHJs) of the donor polymer PTQ10 and molecular acceptor IDIC are investigated. PTQ10:IDIC BHJs are shown to be particularly promising for low cost organic solar cells (OSCs). It is found that both PTQ10 and IDIC show remarkably high crystallinity in optimized BHJs, with GIWAXS data indicating pi‐pi stacking coherence lengths of up to 8 nm. Exciton‐exciton annihilation studies indicate long exciton diffusion lengths for both neat materials (19 nm for PTQ10 and 9.5 nm for IDIC), enabling efficient exciton separation with half lives of 1 and 3 ps, despite the high degree of phase segregation in this blend. Transient absorption data indicate exciton separation leads to the formation of two spectrally distinct species, assigned to interfacial charge transfer (CT) states and separated charges. CT state decay is correlated with the appearance of additional separate charges, indicating relatively efficient CT state dissociation, attributed to the high crystallinity of this blend. The results emphasize the potential for high material crystallinity to enhance charge separation and collection in OSCs, but also that long exciton diffusion lengths are likely to be essential for efficient exciton separation in such high crystallinity devices. [ABSTRACT FROM AUTHOR]

Pressure‐induced polymerization (PIP) of aromatics is a novel method for constructing sp3‐carbon frameworks, and nanothreads with diamond‐like structures were synthesized by compressing benzene and its derivatives. Here by compressing a benzene‐hexafluorobenzene cocrystal (CHCF), H‐F‐substituted graphane with a layered structure in the PIP product was identified. Based on the crystal structure determined from the in situ neutron diffraction and the intermediate products identified by gas chromatography‐mass spectrum, we found that at 20 GPa CHCF forms tilted columns with benzene and hexafluorobenzene stacked alternatively, and leads to a [4+2] polymer, which then transforms to short‐range ordered H‐F‐substituted graphane. The reaction process involves [4+2] Diels–Alder, retro‐Diels–Alder, and 1‐1′ coupling reactions, and the former is the key reaction in the PIP. These studies confirm the elemental reactions of PIP of CHCF for the first time, and provide insight into the PIP of aromatics. Short‐range ordered H,F‐substituted graphane was obtained by compressing benzene and hexafluorobenzene cocrystals. By using neutron diffraction and GC‐MS, the reaction process and elementary reactions were identified. The reaction process involves [4+2]Diels–Alder, retro‐Diels–Alder, and 1‐1′ coupling reactions, and the Diels–Alder reaction is the key reaction in the polymerization process. [ABSTRACT FROM AUTHOR]

Abstract: Nonfullerene acceptors (NFAs) in blends with highly crystalline donor polymers have been shown to yield particularly high device voltage outputs, but typically more modest quantum yields for photocurrent generation as well as often lower fill factors (FF). In this study, we employ transient optical and optoelectronic analysis to elucidate the factors determining device photocurrent and FF in blends of the highly crystalline donor polymer PffBT4T‐2OD with the promising NFA FBR or the more widely studied fullerene acceptor PC71BM. Geminate recombination losses, as measured by ultrafast transient absorption spectroscopy, are observed to be significantly higher for PffBT4T‐2OD:FBR blends. This is assigned to the smaller LUMO‐LUMO offset of the PffBT4T‐2OD:FBR blends relative to PffBT4T‐2OD:PC71BM, resulting in the lower photocurrent generation efficiency obtained with FBR. Employing time delayed charge extraction measurements, these geminate recombination losses are observed to be field dependent, resulting in the lower FF observed with PffBT4T‐2OD:FBR devices. These data therefore provide a detailed understanding of the impact of acceptor design, and particularly acceptor energetics, on organic solar cell performance. Our study concludes with a discussion of the implications of these results for the design of NFAs in organic solar cells. [ABSTRACT FROM AUTHOR]

The use of dry transferred graphene as a templating layer to enhance face-to-face stacking in poly(3-hexylthiophene) (P3HT) systems which is widely used for organic optoelectronics is investigated. In contrast to conventional poly(methyl methacrylate) (PMMA) assisted wet transferred graphene, dry transferred graphene is found in the current work to be quite suitable for use in the roll-to-roll process due to its lack of PMMA residue, whose removal would require high-temperature annealing. Grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to determine the percentages of P3HT molecules adopting a face-on orientation on the various substrates tested. When a P3HT film with a thickness of 30 nm is produced, the face-on populations of P3HT are prominent on both the dry and wet transferred graphene layers. As the film thickness is increased to 50 nm, the face-on population decreases on the wet transferred graphene surface, but retains high levels on the dry transferred graphene. GIWAXS, near-edge X-ray absorption fine structure, and atomic force microscopy data are combined to propose schematic models for the molecular stacking of P3HTs on the two differently transferred graphene surfaces. [ABSTRACT FROM AUTHOR]

Tunable and selective areal polymer chain alignment method is developed for spin-cast blend films of poly(3-hexylthiophene)(P3HT):[6,6]-phenyl-C61-butlyric methyl ester (PCBM) system by a femtosecond laser process. The chain alignment, phase separation, and molecular structure of the laser exposed P3HT:PCBM films are investigated by grazing incidence wide angle X-ray scattering and micro-Raman analysis. The alkyl chains of P3HT polymer become highly ordered along the polarization axis of the laser. Thus, the amount of desirable face-on configuration for solar cell application is largely enhanced with a subsequent postannealing process. Vertically expanded morphology up to 200 nm on P3HT:PCBM films is also prompted by the laser irradiation without deteriorating intramolecular structure and changing chemical composition. Simultaneously, vertical phase separation of PCBM toward surface is induced at exposed region. [ABSTRACT FROM AUTHOR]

The structure of P3HT in P3HT:PCBM films is examined on a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) substrate subjected to cryo-cooling to low temperature (−143 °C) followed by gradual heating to 50 °C. The behavior of these systems is examined in the absence and presence of an Al electrode on top of the P3HT:PCBM film. At temperatures below −10 °C, only the type-I phase of P3HT is observed. However, the type-II phase of P3HT starts to form near −10 °C, in both the presence and absence of the Al layer. In the system without an Al layer, the type-II phase disappears at 30 °C, but this phase persists to 50 °C in the presence of the Al layer. Concomitant with the formation of the type-II phase, a 1:3 ordered P3HT type-II (1/3,0,0) superlattice peak emerged. The type-II domains tend to form near the Al electrode layer and show a higher degree of alignment than the type-I crystals. [ABSTRACT FROM AUTHOR]

Hole transport materials, perovskite solar cells, small molecule-polymer blend Keywords: hole transport materials; perovskite solar cells; small molecule-polymer blend EN hole transport materials perovskite solar cells small molecule-polymer blend 1 1 1 03/25/21 20210323 NES 210323 Water-soluble CuPc derivatives (TS-CuPc) have a self-assembly phase when present with PEDOT:PSS. Perovskite Solar Cells: Interface Engineering of Perovskite/Hole Transport Layer Using Nano-Network Formation in Small Molecule-Polymer Blend for Efficient Inverted Perovskite Solar Cells (Adv. [Extracted from the article]

Ternary blend approaches are demonstrated as a universal means to improve overall performance of organic photovoltaics (OPVs) in both indoor and outdoor conditions. A comparative study on two donors:one acceptor (2D:1A) and one donor:two acceptors (1D:2A) ternary blends shows that both approaches are universally effective for indoor and outdoor operation; the 1D:2A devices incorporating a nonfullerene acceptor (NFA) benefit from less charge recombination and higher power conversion efficiencies (PCEs) for various irradiation conditions, while the performance of the 2D:1A blends depends on the emission spectrum of the incident light source. The synergistic merits of NFAs and ternary structure in the 1D:2A ternary OPVs secure better performance and generality regardless of the incident lighting. A combination of experimental and theoretical analyses unveils that NFAs optimize packing and arrangement of molecules to build efficient cascade ternary junctions in the 1D:2A blends, which can be important design guidelines for the third component in ternary OPVs. The optimized 1D:2A ternary OPV exhibits a new record PCE of 25.6% under a 200 lux light‐emitting diode (LED) and 26.4% under a 1000 lux LED, and superior durability under industrial relevant thermal stress, suggesting new opportunities in diverse practical applications challenging the currently dominant PV technologies. [ABSTRACT FROM AUTHOR]

Here, it is investigated whether an energetic cascade between mixed and pure regions assists in suppressing recombination losses in non‐fullerene acceptor (NFA)‐based organic solar cells. The impact of polymer‐NFA blend composition upon morphology, energetics, charge carrier recombination kinetics, and photocurrent properties are studied. By changing film composition, morphological structures are varied from consisting of highly intermixed polymer‐NFA phases to consisting of both intermixed and pure phase. Cyclic voltammetry is employed to investigate the impact of blend morphology upon NFA lowest unoccupied molecular orbital (LUMO) level energetics. Transient absorption spectroscopy reveals the importance of an energetic cascade between mixed and pure phases in the electron–hole dynamics in order to well separate spatially localized electron–hole pairs. Raman spectroscopy is used to investigate the origin of energetic shift of NFA LUMO levels. It appears that the increase in NFA electron affinity in pure phases relative to mixed phases is correlated with a transition from a relatively planar backbone structure of NFA in pure, aggregated phases, to a more twisted structure in molecularly mixed phases. The studies focus on addressing whether aggregation‐dependent acceptor LUMO level energetics are a general design requirement for both fullerene and NFAs, and quantifying the magnitude, origin, and impact of such energetic shifts upon device performance. [ABSTRACT FROM AUTHOR]

The unique properties of organic photovoltaics (OPVs) offer great promise in emerging applications such as wearable electronics or the Internet of Things. For their successful utilization, OPV operation should be designed for versatile irradiation circumstances in addition to solar light since they should be capable of providing electric power when there is no sunlight or when they operate indoors. Here, a quaternary OPV (Q‐OPV) as a semitransparent, colorful energy platform that operates efficiently under both solar and artificial light irradiation is demonstrated. The experimentally optimized Q‐OPV shows a broadened spectral response and improved charge transport process with suppressed recombination, thereby providing high output powers that are sufficient to autonomously operate low‐power electronic devices. In addition, the Q‐OPV benefits from improved morphological stability with a reduced driving force for grain growth by the increased entropy in the quaternary blend system. The important features of the Q‐OPV platform such as semitransparency, high tolerance to film thickness, and color codability, while pursuing the improved performance and thermal durability, further open new opportunities as an all‐day (24/7/365) power generator in broad practical applications. [ABSTRACT FROM AUTHOR]

The figure illustrates the roll‐to‐roll transferred graphene combining with solution process aiming for flexible high efficiency devices by adopting MTG (molecular templating growth) effects of conjugated polymers on graphene surface. More details can be found in article number 1701099 by Jae‐Hyun Kim, Hyo Jung Kim and co‐workers. [ABSTRACT FROM AUTHOR]

Front Cover: Tunable and selective areal polymer chain alignment method is developed for conducting polymer blend films of poly(3‐hexylthiophene)(P3HT):[6,6]‐phenyl‐C61‐butyric methyl ester (PCBM) system via direct femtosecond laser writing. Interestingly, the P3HT polymer become highly ordered with face‐on configuration along the polarization direction of the laser. Further details can be found in the article by S. Chae, K. H. Jo, S. W. Lee, H.‐S. Keum, H. J. Kim,* J. Choi,* H. H. Lee* on page 537. [ABSTRACT FROM AUTHOR]

Back Cover: Type‐II phase like poly(3‐hexylthiophene) (P3HT) crystals are formed near the interface region of an Al electrode in a full device structure for organic photovoltaic cells by low temperature cooling to −143 °C followed by gradual heating to 30 °C. Concomitant with the formation of the type‐II phase, an 1:3 ordered P3HT type‐II (1/3,0,0) super‐lattice peak emerges in the 2D GI‐SAXS pattern. Further details can be found in the article by S. W. Lee, H.‐S. Keum, H. S. Kim, H. J. Kim,* K. Ahn, D. R. Lee,* J. H. Kim, and H. H. Lee* on page 203. [ABSTRACT FROM AUTHOR]