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Persistent n-doped conjugated polymers were achieved by doping the electron accepting PDNDIV and PFNDIV polymers with ionic (TBACN) or neutral (TDAE) dopants. The great electron affinities, as indicated by the low LUMO levels of PDNDIV (-4.09 eV) and PFNDIV (-4.27 eV), facilitated the chemical reduction from either TBACN or TDAE. The low-lying LUMOs of the neutral polymers PDNDIV and PFNDIV were achieved by incorporation of vinylene spacers between the electron poor NDI units to increase the conjugation length without the use of an electron donor, and this was lowered further by an electron-withdrawing fluorinated N-substituent on the NDI moiety. The polymer radical anions were found to persist for several days under ambient conditions by EPR spectroscopy. A distinguishing and noteworthy feature of these polymers is that they can be consecutively reduced by up to four electrons in acetonitrile. Conductivity measurements demonstrate the prospective impact of PDNDIV and PFNDIV for organic electronics.

While perovskite solar cells have invigorated the photovoltaic research community due to their excellent power conversion efficiencies (PCEs), these devices notably suffer from poor stability. To address this crucial issue, a solution-processable organic chemical inhibition layer (OCIL) was integrated into perovskite solar cells, resulting in improved device stability and a maximum PCE of 16.3%. Photoenhanced self-doping of the fulleropyrrolidine mixture in the interlayers afforded devices that were advantageously insensitive to OCIL thickness, ranging from 4 to 190 nm. X-ray photoelectron spectroscopy (XPS) indicated that the fulleropyrrolidine mixture improved device stability by stabilizing the metal electrode and trapping ionic defects (i.e., I-) that originate from the perovskite active layer. Moreover, degraded devices were rejuvenated by repeatedly peeling away and replacing the OCIL/Ag electrode, and this repeel and replace process resulted in further improvement to device stability with minimal variation of device efficiency.

The synthesis of Al and Fe codoped ZnO colloidal nanocrystals (NCs) using a modified etching-regrowth-doping method is presented. We show that the spectroscopic signatures associated with Fe3+ in ZnO disappear upon introduction of Al3+ donor defects into the ZnO lattice. The presence of Al3+ is confirmed by the appearance of a localized surface plasmon resonance feature indicating excess free carriers in the codoped NCs. These spectral changes suggest that Al3+ doping results in a reduction of Fe3+ dopants to the electron paramagnetic resonance-silent Fe2+ dopants that are stable under ambient conditions. These colloidal NCs provide a potential building block for manipulating magneto-optical properties and plasmon responses in colloidal NCs and higher-order nanostructures. [ABSTRACT FROM AUTHOR]

We report facile and reversible electron storage in colloidal SrTiO3 nanocrystals using photochemical and redox titration methods. A very high electron storage capacity (∼180 e− per 7 nm nanocrystal) is achieved which we attribute to the localized nature of added electrons at sub-bandgap trap sites in these colloidal SrTiO3 nanocrystals. The rate of electron accumulation is also found to be much faster with ethylene glycol as the sacrificial reductant compared to ethanol. This work provides key insight and establishes a kinetic bottleneck in the charge trapping processes. [ABSTRACT FROM AUTHOR]

The synthesis of collodial Mn(super 2+) -doped ZnO Mn(super 2+):ZnO quantum dots and the preparation of room temperature ferromagnetic nanocrystalline thin films are reported. A distinct ferromagnetic resonance signal was observed in the electron paramagnetic resonance (EPR) spectra of the ferromagnetic films.

High-temperature magnetic ordering in Mn2+- and Co2+-doped ZnO diluted magnetic semiconductors has been predicted theoretically and confirmed experimentally to have different charge-carrier requirements. This paper summarizes some of these experimental and theoretical results and relates the different carrier polarity requirements for 300 K ferromagnetism in Mn2+:ZnO and Co2+:ZnO to differences in the charge-transfer electronic structures of these two materials. [ABSTRACT FROM AUTHOR]

The calcination of amines activating high-Curie temperature (Tc) ferromagnetism in Mn(super 2+):ZnO was described. The results demonstrated the magnetism of Mn(super 2+): ZnO is critically dependent upon factors other than the transition metal dopants.

A viable qubit must have a long coherence time T2. In molecular nanomagnets, T2 is often limited at low temperatures by the presence of dipole and hyperfine interactions, which are often mitigated through sample dilution, chemical engineering and isotope substitution in synthesis. Atomic-clock transitions offer another route to reducing decoherence from environmental fields by reducing the effective susceptibility of the working transition to field fluctuations. The Cr7Mn molecular nanomagnet, a heterometallic ring, features a clock transition at zero field. Both continuous-wave and spin-echo electron-spin resonance experiments on Cr7Mn samples, diluted via co-crystallization, show evidence of the effects of the clock transition with a maximum T2 390 ns at 1.8 K. We discuss improvements to the experiment that may increase T2 further. [ABSTRACT FROM AUTHOR]

The preparation of colloidal diluted magnetic semiconductor (DMS) nanocrystals are reported of possessing additional quantum-confined conduction band (CB) electrons and describe the use of electron paramagnetic resonance (EPR) spectroscopy to probe the coupling between these electrons and magnetic dopants. This motif of colloidal charged magnetic semiconductor nanocrystals presents attractive new opportunities for studying and potentially manipulating spins in quantum-confined nanostructures prepared by direct chemical methods.