Organic and printed electronics technologies require conductors with a work function that is sufficiently low to facilitate the transport of electrons in and out of various optoelectronic devices. We show that surface modifiers based on polymers containing simple aliphatic amine groups substantially reduce the work function of conductors including metals, transparent conductive metal oxides, conducting polymers, and graphene. The reduction arises from physisorption of the neutral polymer, which turns the modified conductors into efficient electron-selective electrodes in organic optoelectronic devices. These polymer surface modifiers are processed in air from solution, providing an appealing alternative to chemically reactive low-work function metals. Their use can pave the way to simplified manufacturing of low-cost and large-area organic electronic technologies.

No abstract

No abstract

Organic electron-transporting materials are essential for the fabrication of organic p-n junctions, photovoltaic cells, n-channel field-effect transistors, and complementary logic circuits. Rylene diimides are a robust, versatile class of polycyclic aromatic electron-transport materials with excellent thermal and oxidative stability, high electron affinities, and, in many cases, high electron mobilities; they are, therefore, promising candidates for a variety of organic electronics applications. In this review, recent developments in the area of high-electron-mobility diimides based on rylenes and related aromatic cores, particularly perylene- and naphthalene-diimide-based small molecules and polymers, for application in high-performance organic field-effect transistors and photovoltaic cells are summarized and analyzed.

Perylene-3,4,9,10-tetracarboxylic acid diimides (perylene diimides, PDIs) have been used as industrial pigments for many years. More recently, new applications for PDI derivatives have emerged in areas including organic photovoltaic devices and field-effect transistors. This Perspective discusses the synthesis and physical properties of PDI derivatives and their applications in organic electronics.

Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared to the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant nonradiative recombination. In this work, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer state energies. This observation is explained by considering non-radiative charge-transfer state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to (1.45-1.65) eV, i.e. (0.2-0.3) eV higher than for technologies with minimized non-radiative voltage losses. Manuscript: "Intrinsic Non-Radiative Voltage Losses in Fullerene-Based OSCs" J. Benduhn et al.

An electron-transport polymer with good solution processibility, excellent thermal stability, and high electron affinity based on alternating perylene diimide and dithienothiophene units has been synthesized. Electron mobilities as high as 1.3 × 10-2 cm2 V-1 s-1 have been measured in field-effect transistor geometry. The polymer shows broad absorptions throughout the visible and extending into the near-IR. A power conversion efficiency of over 1%, under simulated AM 1.5, 100 mW/cm2, was measured for a single-layer solar cell using this polymer as an acceptor and a polythiophene derivative as a donor.

The two-photon absorption properties of a series of bis dialkylamino- or diarylamino-substituted diphenylpolyenes and bis(styryl)benzenes have been investigated. Two-photon absorption cross sections, δ, as large as 1420 × 10-50 cm4 s/photon-molecule have been observed for molecules with this general bis-donor structure. The effect of the type and length of the conjugated chain and of dialkylamino or diarylamino substitution on the position and magnitude of the peak two-photon absorptivity is reported. The transition dipole moments for the transitions between the ground state and the first excited singlet state (M ge) and between the first and second excited singlet states (M ee ‘) have been estimated using experimental data from the one- and two-photon spectra. It was found that increases in chain length result mainly in an increase in M ge, whereas the addition of donor end groups or going from diphenylpolyene- to phenylene-vinylene-type bridges leads primarily to an increase in M ee ‘. The trends in the energy of the lowest excited singlet states and in the transition moments for the diphenylpolyene series as a function of chain length are in agreement with those calculated by quantum mechanical methods. These results furnish a link between structural features in these classes of molecules and the electronic dipole couplings and state energies that control the strength of the two-photon absorption. In bis(aminophenyl)polyenes containing up to four double bonds (m) the lowest excited singlet state is a Bu state, as opposed to the case of simple polyenes and diphenylpolyenes, for which it is an Ag state for m > 2. The relationship of the state ordering in these systems with the observed values of the radiative and nonradiative decay rates is also discussed.