A large-area module (active area > 20 cm 2 ) with a power conversion efficiency (PCE) of 10.4% (certified at 10.1%) using a non-fullerene blend was demonstrated, which is by far the highest PCE reported to date. The same module also delivers a power of 40 mW/cm 2 (PCE 22%) under indoor lighting. Equally important, PCEs of 12%-14% were achieved for blends processed in ambient and/or without halogenated solvent.

The imidazolium ligand precursors [L1H1H2]Cl and [L2H1 2H2]Cl (H1 = NHCO, H2 = NCHN) for the potentially bidentate and pincer-type amido-NHC ligands were synthesized in 66−78% yields. Selective deprotonation of H2 in these salts with pyridine in the presence of palladium chloride resulted in the monodentate palladium(II) complexes Pd(L1H1)(py)Cl2 and Pd(L2H1 2)(py)Cl2. The use of K2CO3 in pyridine or DMF led to the double and triple deprotonations of the ligand precursors, giving the bis-bidentate and pincer-type palladium(II) complexes PdL1 2 and PdL2(py), respectively. Intriguingly, in certain cases, both the cis and the trans isomers of PdL1 2 were formed and isolated in pure forms. A theoretical study indicates that the trans-PdL1 2 is thermodynamically more stable than the cis isomer (ca. 5.8 kcal mol-1). All the new complexes are characterized by NMR (1D and 2D) and single-crystal X-ray diffraction studies. A systematic study of the new complexes in Suzuki coupling reactions revealed the following order of activities:  Pd(L1H1)(py)Cl2 > PdL2(py) > PdL1 2.

Benzo[d][2,1,3]thiadiazole (BT) is a markedly electron-deficient heterocycle widely employed in the realization of organic semiconductors for applications spanning transistors, solar cells, photodetectors, and thermoelectrics. In this contribution, we implement the corresponding isomer, benzo [d][1,2,3]thiadiazole (isoBT), along with new 6-fluoro-isoBT and 5,6-difluoro-isoBT units as synthons for constructing alternating copolymers with tetrathiophene (P1−P3). New isoBT-based small molecules as well as the corresponding BTquaterthiophene based polymers (P4−P6) are synthesized and characterized to probe architectural, electronic structural, and device performance differences between the two families. The results demonstrate that isoBT complements BT in enabling highperformance optoelectronic semiconductors with P3 exhibiting hole mobilities surpassing 0.7 cm 2 /(V s) in field-effect transistors and power conversion efficiencies of 9% in bulk-heterojunction solar cells.

Benzene-based 1,1-dicyanomethylene-3-indanone (IC) derivatives have been widely utilized as the end-group to construct acceptor−donor−acceptor type nonfullerene acceptors (A−D−A type NFAs). The extension of the end-group conjugation of nonfullerene acceptors (NFAs) is a rational strategy to facilitate intermolecular stacking of the end-groups which are responsible for efficient electron transportation. A bicyclic benzothiophene-based end-group acceptor, 2-(3-oxo-2,3-dihydro-1H-benzo[b]cyclopenta [d]thiophen-1-ylidene)malononitrile, denoted as α-BC was designed and synthesized. The Knoevenagel condensation of the unsymmetrical 1,3-diketo-precursor with one equivalent of malononitrile selectively reacts with the keto group attached at the α-position of the thiophene unit, leading to the isomerically pure benzothiophene-fused α-BC. The well-defined α-BC with extended conjugation was condensed with three different laddertype diformylated donors to form three new A−D−A NFAs named BDCPDT-BC, DTCC-BC, and ITBC, respectively. The corresponding IC-based BDCPDT-IC, DTCC-IC, and ITIC model compounds were also synthesized for comparison. The incorporation of the electron-rich benzothiophene unit in the end-group upshifts the lowest unoccupied molecular orbital energy levels of the NFAs, which beneficially enlarges the V oc values. On the other hand, the benzothiophene unit in α-BC not also imparts an optical transition in the shorter wavelengths around 340−400 nm for a better light harvesting ability but also promotes the antiparallel π−π stacking of the end-groups for efficient electron transport. The organic photovoltaic cell devices using a PBDB-T polymer and BC-based NFAs all showed the improved V oc and J sc values. The BDCPDT-BC-and DTCC-BCbased devices exhibited a power conversion efficiency (PCE) of 10.82 and 10.74%, respectively, which outperformed the corresponding BDCPDT-IC-, and DTCC-IC-based devices (9.33 and 9.25%). More importantly, the ITBC-based device delivered the highest PCE of 12.07% with a J sc of 19.90 mA/cm 2 , a V oc of 0.94 V, and an fill factor of 64.51%, representing a 14% improvement relative to the traditional ITIC-based device (10.05%).

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