An interesting and important question emerges with the rapid advances of the highly efficient fused‐ring nonfullerene acceptors; that is, how the acceptor molecules form aggregates in its blended film with a donor polymer/small molecule so as to offer highly efficient exciton diffusion and electron transport? To answer this question, a new acceptor molecule, 3,9‐bis(5‐methylene‐4‐one‐6‐(1,1‐dicyanomethylene)‐cyclopenta[c]thiophen‐2,8‐dimethyl)‐5,5,11,11‐tetrakis(4‐n‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (ITCT‐DM), is designed and synthesized herein and its unique interpenetrating J‐architecture is presented in which the acceptor molecules form compacted and displaced ππ‐stacks with the distances of 3.1−4.2 Ǻ. Again the crystal structure data are correlated with the grazing‐incidence X‐ray diffraction (GIXRD) data of the pure acceptor and its polymer:acceptor blended films, which gives a clearer picture about the origins of the acceptor's GIXRD signals in both the pure and its blended films. Again, these results unveil the key roles of the uses of 1,8‐diiodooctane (DIO) and thermal annealing treatment in optimizing the acceptor phase morphologies in the donor:acceptor blended film, and the combination of the thermal annealing and DIO treatment leads to obtain higher crystallinity for both the donor and acceptor phases, more compacted packing, and finer morphologies. A power conversion efficiency of 10.5% is obtained.

Three 4,4-difluoro-4-bora-3a,4a-diaza-s-indancene (BODIPY)-based small molecule donors H-T-BO, Br-T-BO, and DIMER were synthesized and fully characterized. Although modification at the meso position has a subtle influence on the light-harvesting ability, energy levels, and phase sizes, it has a striking effect on the packing behavior in solid film as two-dimension grazing incidence X-ray diffraction (2D GIXRD) and X-ray diffraction (XRD) confirm. Br-T-BO exhibits better packing ordering than H-T-BO in pristine film, which is beneficial from reinforced intermolecular interaction from halogen atoms. However, when [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) is blended, no diffraction patterns corresponding to the monomeric donor can be seen from the XRD data and both H-T-BO- and Br-T-BO-based blend films give a slightly blue-shifting absorption peak with respect to their neat ones, both of which imply destruction of the crystalline structure. As for DIMER, the enhancement of the intermolecular interaction arises not only from the expansion of the backbone but the "steric pairing effect" brought on by its twisted structure. When blended with PC71BM, the diffraction patterns of DIMER are, however, kept well and the absorption peak position remains unchanged, which indicates the ordered packing of DIMER is held well in blend film. In coincidence with the fact that packing ordering improves from H-T-BO to Br-T-BO and DIMER in pristine films and the ordered packing of DIMER even in blend film, DIMER-based devices show the highest and most balanced hole/electron mobility of 1.16 × 10(-3)/0.90 × 10(-3) cm(2) V(-1) s(-1)with respect to Br-T-BO (4.71 × 10(-4)/2.09 × 10(-4) cm(2) V(-1) s(-1)) and H-T-BO (4.27 × 10(-5)/1.00 × 10(-5) cm(2) V(-1) s(-1)) based ones. The short-circuit current density of the three molecule-based cells follows the same trend from H-T-BO (6.80) to Br-T-BO (7.62) and then to DIMER (11.28 mA cm(-2)). Finally, the H-T-BO-, Br-T-BO-, and DIMER-based optimal device exhibits a power conversion efficiency of 1.56%, 1.96%, and 3.13%, respectively.

Three asymmetric non-fullerene acceptors (LL2, LL3, and LL4) are designed and synthesized with one norbornyl-modified 1,1-dicyanomethylene-3indanone (CBIC) terminal group and one chlorinated 1,1-dicyanomethylene-3-indanone (IC-2Cl) terminal group. The three-dimensional shape-persistent CBIC terminal group can effectively enhance the solubility and tune the packing mode of acceptors. Compared with their symmetric counterparts (LL2-2Cl, LL3-2Cl, and LL4-2Cl) bearing two IC-2Cl terminals, the asymmetric acceptors show improved solubilities, giving rise to enhanced crystallinity and favored nanomorphology for charge transport in the blend films with PBDB-T. Asymmetric acceptors based organic solar cells (OSCs) also show much lower voltage loss due to their higher E CT and EQE EL values. Therefore, they exhibit 17−27% higher power conversion efficiency (PCE) than OSCs based on the corresponding symmetric acceptors. Among these six acceptors, LL3 with a central benzotriazole core shows the best PCE of 16.82% with an outstanding J sc of 26.97 mA cm −2 and a low nonradiative voltage loss (ΔV nr ) of 0.18 V, the best values for PBDB-T based OSCs. The J sc and ΔV nr also represent the best reported for asymmetric non-fullerene acceptors-based OSCs to date. The results demonstrate that the combination of the unique CBIC terminal group with the asymmetric strategy is a promising way to enhance the performance of OSCs.

Increasing the photoluminescence quantum yield (PLQY) of narrow bandgap acceptors is of critical importance to suppress the nonradiative voltage loss (ΔVnr) in organic solar cells (OSCs). Herein, two acceptors, SM16 and SM16‐R, with an identical backbone but different terminal groups (norbornenyl modified 1,1‐dicyanomethylene‐3‐indanone and dimethyl substituted 1,1‐dicyanomethylene‐3‐indanone) are designed and synthesized. Compared with SM16‐R, SM16 displays better solubility, higher PLQY, and more favorable nanomorphology when blended with polymer donor PBDB‐T. PBDB‐T:SM16‐based OSCs yield a ΔVnr as low as 0.145 V. Using SM16 as the third component, a high power conversion efficiency of 17.1% is achieved in the ternary OSCs based on PBDB‐T:Y14:SM16, considerably higher than that of the binary devices based on PBDB‐T:Y14 or PBDB‐T:SM16. These results highlight that enhancing the PLQY of low bandgap acceptor via terminal group engineering strategy is highly effective to reduce ΔVnr of OSCs.

Herein, norbornyl (NB), ab ulkya nnular nonconjugated spacer,i sm elded into p systems to construct two groups of ladder-type room-temperature phosphorescence (RTP) luminogens.T he effect of the NB on p-p interactions, packing modes and RTP performance is explored systematically.The experimental and computational results demonstrate the versatility of NB in reducing p-p distances and synergistically intensifying the intermolecular interactions,w hich not only induces intersystem crossing from S 1 to T n but also diminishes the nonradiative decayo ft riplet excitons.I mpressively,1 800-fold phosphorescence lifetime enhancement is achieved in comparison with the reference compounds without NB.T he molecular packing and RTPp erformance can be further modulated by the length of the backbones and terminal end-groups.Itisquite peculiar that NB-annulated phthalic acid exhibits reversible photochromism in the solid state,likely due to the formation of persistent radical pairs.Our study paves an ingenious avenue towards enhancing intermolecular interactions and provides significant implications for ab etter comprehensive understanding of the origin of their RTPa nd the inherent photophysical mechanism.

No abstract

No abstract

An N719 based high‐efficiency binary cathode buffer layer (CBL) was developed. The work‐function of the Al cathode was precisely modulated between −3.3 and −3.9 eV due to the cation re‐arrangement between the binary components, induced by finely controlling the binary‐components weight ratio. A 10.50%‐ and 11.46%‐efficiency organic solar cells were reported with the use of the N719 and the binary CBL, respectively.