RESUMEN
Manipulating the conjugated backbone of small molecule acceptors (SMAs) is of particular importance in developing efficient organic solar cells (OSCs). Recently, trimers and other multi-arm SMAs have been found to be able to provide more intermolecular interaction, demonstrating excellent molecular stacking and device performance. However, the synthesis of this type of SMA usually relies on tristin or polystin compounds. Instead, expanding multiple arms in the central cores of SMAs is relatively simple and not restricted by tin compounds. Based on the quinoxaline core, two kinds of multi-arm SMAs, FQx-IC and TQx-IC with 4 and 3 arms, have been developed in this work. Compared to FQx-IC, TQx-IC exhibits an ordered face-on molecular orientation, appropriate film-forming process, and more favorable phase separation morphology and balanced charge transport. When blended with the polymer donor D18, OSCs based on TQx-IC achieve a power conversion efficiency (PCE) of 17.36%, which is superior to the device based on D18:FQx-IC (16.24%). In addition, using the ternary strategy of incorporating the TQx-IC into the D18:Y6 system, an excellent PCE of 18.82% is achieved. Therefore, this multi-arm molecular design strategy has great potential for regulating molecular stacking, absorption, and the corresponding device performance.
RESUMEN
For organic solar cells (OSCs), obtaining a high open circuit voltage (VOC) is often accompanied by the sacrifice of the circuit current density (JSC) and filling factor (FF), and it is difficult to strike a balance between VOC and JSC × FF. The trade-off of these parameters is often the critical factor limiting the improvement of the power conversion efficiency (PCE). Extended backbone conjugation and side chain engineering of non-fullerene acceptors (NFAs) are effective strategies to optimize the performance of OSCs. Herein, based on the quinoxaline central core and branched alkyl chains at the ß position of the thiophene unit, we designed and synthesized three NFAs with different sized cores. Interestingly, Qx-BO-3 with a smaller central core showed better planarity and more appropriate crystallinity. As a result, PM6:Qx-BO-3-based devices obtained more suitable phase separation, more efficient exciton dissociation, and charge transport properties. Therefore, the OSCs based on PM6:Qx-BO-3 yielded an outstanding PCE of 17.03%, significantly higher than the devices based on PM6:Qx-BO-1 (10.57%) and PM6:Qx-BO-2 (11.34%) although the latter two devices have lower VOC losses. These results indicated that fine-tuning the central core size can effectively optimize the molecular geometry of NFAs and the film morphology of OSCs. This work provides an effective method for designing high-performance NFA-OSCs with high VOCs.
RESUMEN
Drug delivery in target regions could make extraordinary progress in chemoselective therapies. A novel preferred coordination (PC) strategy referring to proactive interacting with open active sites to replace previous occupation by ion-exchange for controlling release of drug molecules is well-constructed. Two topological types of MOF-In1 (Schläfli symbol: (4,8)-connected of (410·615·83)(45·6)2) and MOF-In2 (Schläfli symbol: (4,4)-connected of (66)) show the specific way. Increasing node connectivity as well as the trapping of guest OH- anions, 5-fluorouracil (5-FU) is preferentially captured into the MOF-In1, which exhibits an outstanding loading capacity around 34.32 wt %. 19F NMR spectroscopy was further employed to investigate host-guest interaction and reveal the binding constant (Ka = 3.84 × 102 M-1). Meanwhile, the controlled release of 5-FU in a simulated human body with liquid phosphate-buffered saline solution by biofriendly Zn2+-triggered is realized. With an elevated Zn2+ concentration, the drug release will be enhanced. This efficient strategy for MOFs as multifunctional drug carrier opens a new avenue for biological and medical applications.