Eco-friendly fabrication of 4% efficient organic solar cells from surfactant-free P3HT:ICBA nanoparticle dispersions.

Photo-active layers from non-stabilized P3HT:ICBA nanoparticles enable the fabrication of inverted organic solar cells from eco-friendly, alcoholic dispersions. Exhibiting power conversion efficiencies (PCEs) ≈4%, the devices are competitive to state-of-the-art P3HT:ICBA solar cells from chlorinated solvents. Upon thermal annealing, the short circuit current density and consequently the PCE of the inverted solar cells improve radically due to a more intimate contact of the nanoparticles and hence an enhanced charge carrier extraction.

High-performance polymer semiconducting heterostructure devices by nitrene-mediated photocrosslinking of alkyl side chains.

Heterostructures are central to the efficient manipulation of charge carriers, excitons and photons for high-performance semiconductor devices. Although these can be formed by stepwise evaporation of molecular semiconductors, they are a considerable challenge for polymers owing to re-dissolution of the underlying layers. Here we demonstrate a simple and versatile photocrosslinking methodology based on sterically hindered bis(fluorophenyl azide)s.

Role of delta-hole-doped interfaces at Ohmic contacts to organic semiconductors.

An electromodulated absorption spectroscopy study of the contact between an organic semiconductor (OSC) poly(2,5-dialkoxy-p-phenylenevinylene) and p-doped poly(3,4-ethylenedioxythiophene) electrodes of different work functions (phivac) reveals direct evidence for the formation of a hole-doped layer at the OSC interface in equilibrium with high-phivac electrodes. When the hole density at this interface exceeds a few 10(11) cm(-2), degenerate "bandlike" polaron states emerge. This appears to be crucial to furnish efficient carrier injection into the bulk of the OSC to achieve Ohmic injection.

Direct evidence for the role of the madelung potential in determining the work function of doped organic semiconductors.

The work function of a model degenerately doped organic semiconductor p-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) can be systematically tuned over an eV-wide range by exchanging excess matrix protons with spectator cations, without altering the organic semiconductor doping level or polaron density. Ultraviolet photoelectron spectroscopy reveals this to arise not from an interface dipole, but from a bulk effect due to a shift in the Madelung potential set up by the local counter- and spectator-ion structure at the polaron sites. Electrostatic modeling of this potential is in agreement with the observed shift in carrier energetics.

Controlled insulator-to-metal transformation in printable polymer composites with nanometal clusters.

Although organic semiconductors have received the most attention, the development of compatible passive elements, such as interconnects and electrodes, is also central to plastic electronics. For this, ligand-protected metal-cluster films have been shown to anneal at low temperatures below 250 degrees C to highly conductive metal films, but they suffer from cracking and inadequate substrate adhesion. Here, we report printable metal-cluster-polymer nanocomposites that anneal to a controlled-percolation nanostructure without complete sintering of the metal clusters.

Large damage threshold and small electron escape depth in X-ray absorption spectroscopy of a conjugated polymer thin film.

The information depth of near-edge X-ray absorption fine structure spectroscopy in the total electron yield mode (TEY-NEXAFS) is given by the escape depth of the TEY electrons z(TEY). This is determined by the effective ranges both of the inelastically scattered secondary electrons and of the primary excited electron before they thermalize below the vacuum level. For regioregular poly(3-hexylthiophene) (rreg-P3HT) thin films, we have measured the total electron emission efficiency to be 0.