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Molecular doping of organic semiconductors is often used to enhance their charge transport characteristics. Despite its success, however, most studies to date concern p‐doping with considerably fewer reports involving n‐dopants. Here, n‐doping of organic thin‐film transistors (OTFTs) based on several non‐fullerene acceptor (NFA) molecules using the recently developed diquat (DQ) as a soluble molecular dopant is reported. The low ionization potential of DQ facilitates efficient electron transfer and subsequent n‐doping of the NFAs, resulting in a consistent increase in the electron field‐effect mobility. Solution‐processed BTP‐eC9 and N3‐based OTFTs exhibit significant increase in the electron mobility upon DQ doping, with values increasing from 0.02 to 0.17 cm2 V–1 s–1 and from 0.2 to 0.57 cm2 V–1 s–1, respectively. A remarkable electron mobility of >1 cm2 V–1 s–1 is achieved for O‐IDTBR transistors upon optimal doping with DQ. The enhanced performance originates primarily from synergistic effects on electronic transport and changes in morphology, including: i) significant reduction of contact resistances, ii) formation of larger crystalline domains, iii) change of preferred crystal orientation, and iv) alteration in molecular packing motif. This work demonstrates the universality of DQ as an electronic additive for improving electron transport in OTFTs. [ABSTRACT FROM AUTHOR]

Hydrogen is attractive as an abundant source for clean and renewable energy. However, due to its highly flammable nature in a range of concentrations, the need for reliable and sensitive sensor/monitoring technologies has become acute. Here a solid‐state hydrogen sensor based on solution‐processable p‐type semiconductor copper thiocyanate (CuSCN) is developed and studied. Sensors incorporating interdigitated electrodes made of noble metals (gold, platinum, palladium) show excellent response to hydrogen concentration down to 200 ppm while simultaneously being able to operate reversibly at room temperature and at low power. Sensors incorporating Pd electrodes show the highest signal response of 179% with a response time of ≈400 s upon exposure to 1000 ppm of hydrogen gas. The experimental findings are corroborated by density functional theory calculations, which highlight the role of atomic hydrogen species created upon interaction with the noble metal electrode as the origin for the increased p‐type conductivity of CuSCN during exposure. The work highlights CuSCN as a promising sensing element for low‐power, all‐solid‐state printed hydrogen sensors. [ABSTRACT FROM AUTHOR]

Abstract: Achieving efficient bulk‐heterojunction (BHJ) solar cells from blends of solution‐processable small‐molecule (SM) donors and acceptors is proved particularly challenging due to the complexity in obtaining a favorable donor–acceptor morphology. In this report, the BHJ device performance pattern of a set of analogous, well‐defined SM donors—DR3TBDTT (DR3), SMPV1, and BTR—used in conjunction with the SM acceptor IDTTBM is examined. Examinations show that the nonfullerene “All‐SM” BHJ solar cells made with DR3 and IDTTBM can achieve power conversion efficiencies (PCEs) of up to ≈4.5% (avg. 4.0%) when the solution‐processing additive 1,8‐diiodooctane (DIO, 0.8% v/v) is used in the blend solutions. The figures of merit of optimized DR3:IDTTBM solar cells contrast with those of “as‐cast” BHJ devices from which only modest PCEs <1% can be achieved. Combining electron energy loss spectrum analyses in scanning transmission electron microscopy mode, carrier transport measurements via “metal‐insulator‐semiconductor carrier extraction” methods, and systematic recombination examinations by light‐dependence and transient photocurrent analyses, it is shown that DIO plays a determining role—establishing a favorable lengthscale for the phase‐separated SM donor–acceptor network and, in turn, improving the balance in hole/electron mobilities and the carrier collection efficiencies overall. [ABSTRACT FROM AUTHOR]

A simple approach that enables a consistent enhancement of the electron extracting properties of the widely used small‐molecule Phen‐NaDPO and its application in organic solar cells (OSCs) is reported. It is shown that addition of minute amounts of the inorganic molecule Sn(SCN)2 into Phen‐NaDPO improves both the electron transport and its film‐forming properties. Use of Phen‐NaDPO:Sn(SCN)2 blend as the electron transport layer (ETL) in binary PM6:IT‐4F OSCs leads to a remarkable increase in the cells' power conversion efficiency (PCE) from 12.6% (Phen‐NaDPO) to 13.5% (Phen‐NaDPO:Sn(SCN)2). Combining the hybrid ETL with the best‐in‐class organic ternary PM6:Y6:PC70BM systems results to a similarly remarkable PCE increase from 14.2% (Phen‐NaDPO) to 15.6% (Phen‐NaDPO:Sn(SCN)2). The consistent PCE enhancement is attributed to reduced trap‐assisted carrier recombination at the bulk‐heterojunction/ETL interface due to the presence of new energy states formed upon chemical interaction of Phen‐NaDPO with Sn(SCN)2. The versatility of this hybrid ETL is further demonstrated with its application in perovskite solar cells for which an increase in the PCE from 16.6% to 18.2% is also demonstrated. [ABSTRACT FROM AUTHOR]