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Various types of Lewis bases have been employed to enhance the performance and stability of perovskite solar cells (PSCs) by passivating the active layer. The cyano (CN) group is a weak Lewis base, the effect of which on the passivation of the perovskite layer is unclear. In this study, we employed simple CN-containing compounds, specifically three isomers of dicyanobenzene (DCB) (1,2-DCB, 1,3-DCB, and 1,4-DCB), as passivation agents for the perovskite layer. Our investigation revealed that these compounds exhibited notable interactions with the perovskite film. They effectively removed residual lead iodide, enhanced crystallinity, enlarged perovskite grain size, and reduced trap density. Consequently, these enhancements resulted in a significant increase in the power conversion efficiency (PCE) and ambient storage stability of the passivated PSCs. Among the three DCB isomers, 1,3-DCB demonstrated the most effective passivation, leading to a remarkable increase in PCE, with a maximum of 21.07%, compared to a PCE of 18.33% for the non-passivated cell. These results confirm that the basic cyano (CN) group efficiently interacts with Pb2+ ions and suggest that CN-containing compounds may represent a promising class of passivation agents for achieving high-performance and stable PSCs. [ABSTRACT FROM AUTHOR]

Rapidly growing research interest in the field of printed electronics, especially polymer-based organic thin film transistors (OTFTs) and organic photovoltaics (OPVs), stems from the dramatically improved performance of these devices, which become competitive to the amorphous silicon-based counterparts. The performance enhancement of polymer OTFTs and OPVs is largely attributed to the progress made in the development of polymer semiconductor materials. Therefore exploration of new building blocks for developing high-performance polymer semiconductors has been an area of extensive research. This article provides an overview of new building blocks including 21 electron acceptors and 20 electron donors, which were developed over the past three years for constructing π-conjugated polymers, particularly donor–acceptor (D–A) type polymers. Polymers containing these building blocks have shown very promising performance as active semiconductors in OTFTs and OPVs. Rationales for the structural design and the device performance of the polymers based on these new building blocks are discussed. [ABSTRACT FROM AUTHOR]

In this study, azothiazole, namely (E)-1,2-di(thiazol-2-yl)diazene, is used as a building block to construct π-conjugated polymer semiconductors. It is found that azothiazole is a strong electron withdrawing moiety and suitable as an electron acceptor unit to form donor–acceptor (D–A) polymers. Two D–A polymers comprising azothiazole as the acceptor and bithiophene and thieno[3,2-b]thiophene as the donors, respectively, are synthesized. These polymers have small band gaps (∼1.2–1.3 eV) and low energy levels. When being used as channel semiconductors in organic thin film transistors, they show promising p-channel field effect transistor performance with hole mobility as high as 0.019 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

Indigo is for the first time used as a building block to construct polymer semiconductors for organic thin film transistors (OTFTs). Two donor–acceptor polymers using indigo as the acceptor and bithiophene as the donor are synthesized via Stille coupling polymerization. Two types of acyl groups, 2-hexldecanoyl (for polymer P1) and 2-octyldodecanoyl (for polymer P2), are utilized as solubilizing side chains. These polymers possess very deep highest-occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, due to the strong electron accepting capability of the indigo moiety. In OTFT devices, characteristic n-type semiconductor performance with electron mobility of up to ∼10−3 cm2 V−1 s−1 is observed. [ABSTRACT FROM AUTHOR]

The influence of the side chain on the molecular organization and charge transport performance of diketopyrrolopyrrole-quaterthiophene copolymers (PDQTs) was studied. It was found that, by increasing the side chain length from 2-octyldodecyl (PDQT-20) to 2-decyltetradecyl (PDQT-24), the mobility increased from 2.10 cm2 V−1 s−1 up to 3.37 cm2 V−1 s−1 in organic thin film transistors (OTFTs). The increase was found to be due to the improved surface morphology, rather than the changes in crystallinity and π–π stacking distance. A new side chain substituent, 4-decylhexadecyl, was developed for studying the effects of the bifurcation point of the branched side chains in comparison with 2-octyldodecyl and 2-decyltetradecyl. The 4-decylhexadecyl substituted PDQT (PDQT-26) showed a surge in mobility up to 6.90 cm2 V−1 s−1. The remarkably enhanced charge transport performance observed for PDQT-26 was believed to originate from its much shorter π–π distance (3.68 Å) than those of PDQT-20 (3.79 Å) and PDQT-24 (3.86 Å). The improvement was the result of a farther distance of the bifurcation point of 4-decylhexadecyl from the polymer backbone, which could effectively minimize the steric interference of the bulky side chain branches with the backbone to facilitate the co-facial π–π stacking. [ABSTRACT FROM AUTHOR]