Silver is an ideal candidate for surface plasmon resonance (SPR)-based applications because of its great optical cross-section in the visible region. However, the uses of Ag in plasmon-enhanced spectroscopies have been limited due to their interference via direct contact with analytes, the poor chemical stability, and the Ag(+) release phenomenon. Herein, we report a facile chemical method to prepare shell-isolated Ag nanoparticle/tip. The as-prepared nanostructures exhibit an excellent chemical stability and plasmonic property in plasmon-enhanced spectroscopies for more than one year. It also features an alternative plasmon-mediated photocatalysis pathway by smartly blocking "hot" electrons. Astonishingly, the shell-isolated Ag nanoparticles (Ag SHINs), as "smart plasmonic dusts", reveal a ∼1000-fold ensemble enhancement of rhodamine isothiocyanate (RITC) on a quartz substrate in surface-enhanced fluorescence. The presented "smart" Ag nanostructures offer a unique way for the promotion of ultrahigh sensitivity and reliability in plasmon-enhanced spectroscopies.

The fluorobenzotriazole (FTAZ)‐based copolymer donors are promising candidates for nonfullerene polymer solar cells (PSCs), but suffer from relatively low photovoltaic performance due to their unsuitable energy levels and unfavorable morphology. Herein, three polymer donors, L24, L68, and L810, based on a chlorinated‐thienyl benzodithiophene (BDT‐2Cl) unit and FTAZ with different branched alkyl side chain, are synthesized. Incorporation of a chlorine (Cl) atom into the BDT unit is found to distinctly optimize the molecular planarity, energy levels, and improve the polymerization activity. Impressively, subtle side chain length of FTAZ realizes a dramatic improvement in all the device parameters, as revealed by the short‐current density (Jsc) improved from 7.41 to 20.76 mA cm−2, fill‐factor from 36.3 to 73.5%, and even the open‐circuit voltage (Voc) from 0.495 to 0.790 V. The best power conversion efficiency (PCE) of 12.1% is obtained from the L810‐based device, which is one of the highest values reported for FTAZ‐based PSCs so far. Notably, the corresponding external quantum efficiency curve keeps a very prominent value up to 80% from 500 to 800 nm. The notable performance is discovered from the reduced energy loss, improved molecular face‐on orientation, the down‐shifted energy levels, and optimized absorption coefficient regulated by side‐chain engineering.

A trade‐off between open‐circuit voltage (V OC) and high short‐circuit (J SC) becomes one of the most vital problems limiting further improvement in polymer solar cells' (PSCs) efficiency. In this work, two asymmetric polymer donors PBDT‐F‐2TC and PBDT‐SF‐2TC are designed and synthesized. When blended with a state‐of‐the‐art acceptor IT‐4F with low lowest‐unoccupied molecular orbital level, simultaneously high V OC (up to 0.94 V) and J SC (up to 20.73 mA cm−2) are obtained for both copolymers. Note that the V OC value of 0.94 V is the highest value of PSCs based on IT‐4F reported so far. The simultaneously improved V OC and J SC in resulting devices are discovered from the deep highest‐occupied molecular orbital levels (−5.5 to −5.7 eV) and the hyperchromic effect of the polymers, the small driving force, and the small energy loss during the charge transfer, due to the synergistic effect of asymmetric carboxylate unit and fluorine/sulfur atoms. More importantly, thanks to the asymmetric 2TC, both PBDT‐F‐2TC‐ and PBDT‐SF‐2TC‐based PSCs can be successfully processed by non‐halogenated solvent 1,2,4‐trimethylbenzene (TMB) to yield device efficiencies of 10.29% and 10.39%, respectively, which are the maximum values for non‐fullerene PSCs fabricated using the eco‐friendly solvent TMB.

Enhancing the built-in electric field to promote charge dynamitic process is of great significance to boost the performance of the non-fullerene organic solar cells (OSCs), which has rarely been concerned. In this work, we introduced a cheap ferroelectric polymer as an additive into the active layers of non-fullerene OSCs to improve the device performance. An additional and permanent electrical field was produced by the polarization of the ferroelectric dipoles, which can substantially enhance the built-in electric field. The promoted exciton separation, significantly accelerated charge transport, reduced the charge recombination, as well as the optimized film morphology were observed in the device, leading to a significantly improved performance of the PVDF-modified OSCs with various active layers, such as PM6 : Y6, PM6 : BTP-eC9, PM6 : IT-4F and PTB7-Th : Y6. Especially, a record efficiency of 17.72 % for PM6 : Y6-based OSC and an outstanding efficiency of 18.17 % for PM6 : BTP-eC9-based OSC were achieved.

Herein, an alkylsilyl functionalized alternative (D‐A1) copolymer with high crystallization property as the polymer matrix and planar [1,2‐c:4,5‐c]dithiophene‐4,8‐dione (BDD) block as the second acceptor unit (A2) are selected to construct two D‐A1‐D‐A2 type random copolymers PBDT‐TZ‐BDD‐1/19 and PBDT‐TZ‐BDD‐1/9. It is found that incorporation of a small amount of BDD block into the alkylsilyl functionalized copolymer by random copolymerization can effectively manipulate the energy levels, light absorption, molecular packing and the photovoltaic properties when blended with ITIC (indacenodithieno[3,2‐b]thiophene (IT) as the central donor unit and 2‐ (3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (IC) as end groups). More importantly, random copolymerization provides a beneficial trade‐off that the slightly reduced periodic sequence promotes the compatibility with the acceptor, whereas introduction of planar BDD units allows a preferred face‐on orientation with enhanced π–π stacking of the random copolymer to facilitate the charge transfer. As a result, the random copolymer PBDT‐TZ‐BDD‐1/19 delivers a significantly higher power conversion efficiency (11.02%) than the alternative binary copolymer counterpart together with the remarkably improved short circuit current and fill factor. These results demonstrate that random polymerization of a small amount of planar units into the highly crystalline polymer matrix is a promising strategy to develop high‐performance polymer solar cells.

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A deep highest occupied molecular orbital (HOMO) level is a prerequisite for polymer donor material to boost the organic solar cells (OSCs) performance by achieving high open circuit voltage (V oc ). Abandoning the traditional concept of donor−acceptor (D-A) structure, two copolymers PBTZ-4TC and PBTZ-C4T based on acceptor 1 -π-acceptor 2 (A 1 -π-A 2 ) architecture, where thiophene as the bridge, the difluorinated benzotriazole (BTZ) as A 1 unit alternating copolymerized with 4,4′dicarboxylate-substituted difluorotetrathiophene (4TC) and 3,3′-dicarboxylate-substituted difluorotetrathiophene (C4T) as A 2 , respectively, are developed. Because of the double acceptor blocks with high electron affinity, both A 1 -π-A 2 type copolymers possess the lower HOMO levels of 5.52−5.56 eV, which are lower than most D-A type donors. Polymer PBTZ-4TC and PBTZ-C4T have the same backbone but only differ with the position of carboxylate substituent on the A 2 unit. Intriguingly, subtle optimizing the position of the carboxylate-substitute causes a significantly difference on the properties of the A 1 -π-A 2 type copolymers. PBTZ-C4T with more planar geometry is demonstrated with better light absorption, higher crystallinity, more pronounced temperature-dependent aggregation effect, and favorable bulk heterojunction morphology but with slightly higher HOMO level and more emission energy loss relative to the PBTZ-4TC. The PBTZ-C4T device exhibits the higher power conversion efficiency (PCE) of 9.34% than the PBTZ-4TC-based one (8.75%). These results reveal that concept of A 1 -π-A 2 type copolymers not only can afford more flexibility in tuning the energy levels to achieve the deep HOMO levels but also can provide a facial strategy to greatly enrich the types of polymer donors for high-performance OSCs. KEYWORDS: organic solar cells, acceptor 1 -π-acceptor 2 (A 1 -π-A 2 ) copolymers, more planar geometry, deep energy level, high performance

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