Organic-inorganic Device Research Articles

Cold denaturation induces inversion of dipole and spin transfer in chiral peptide monolayers.

Chirality-induced spin selectivity is a recently-discovered effect, which results in spin selectivity for electrons transmitted through chiral peptide monolayers. Here, we use this spin selectivity to probe the organization of self-assembled α-helix peptide monolayers and examine the relation between structural and spin transfer phenomena. We show that the α-helix structure of oligopeptides based on alanine and aminoisobutyric acid is transformed to a more linear one upon cooling. This process is similar to the known cold denaturation in peptides, but here the self-assembled monolayer plays the role of the solvent. The structural change results in a flip in the direction of the electrical dipole moment of the adsorbed molecules. The dipole flip is accompanied by a concomitant change in the spin that is preferred in electron transfer through the molecules, observed via a new solid-state hybrid organic–inorganic device that is based on the Hall effect, but operates with no external magnetic field or magnetic material.

Fabrication and electrical properties of an organic–inorganic device based on Coumarin 30 dye

A Coumarin 30/p-Si organic-inorganic device was fabricated by forming a Coumarin 30 thin film on a p-Si semiconductor. The resulting structure had excellent rectifying properties. Electrical parameters of the structure were determined from current–voltage (I–V) measurements in the temperature range 300–380K. While the barrier height (ϕb) increased with increasing temperature, the ideality factor and series resistance of the diode decreased. I–V measurements of the structure were also performed under a solar simulator with AM1.5 filter and 100mW/cm2 illumination intensity. The structure had 59μA short-circuit current and 337mV open-circuit voltage. Furthermore, capacitance–voltage (C–V) measurements of an Al/Coumarin 30/p-Si diode were carried out at various frequencies. The ϕb value obtained by using C–V values was compared with that obtained by using I–V data.

Electronic and Photovoltaic Properties of p-Si/PCBM:MEH-PPV Organic-Inorganic Hybrid Photodiode

The photovoltaic and electronic properties of p-Si/poly[2-methoxy,5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV):[6, 6]-phenyl C61-butyric acid methyl ester (PCBM) organic-inorganic device have been investigated. The current–voltage characteristic of p-Si/PCBM:MEH-PPV photodiode includes series resistance effect and the diode indicates a non-ideal behavior. The photovoltaic effect in p-Si/PCBM:MEH-PPV photodiode is based on the formation of excitons and subsequent dissociation and charge collection at the electrodes. It is evaluated that p-Si/PCBM:MEH-PPV device is a photodiode with Voc of 84 mV and Isc of 3.47 nA electronic parameters.

Octadecyltriethoxysilane Surface Modification of Zinc Oxide

AbstractZinc Oxide (ZnO) is actively investigated for hybrid organic inorganic device applications. The interface greatly influences the electronic properties of these devices. Molecular surface modification of ZnO is being investigated for its potential to control the alignment of energy levels, charge transfer, as well as, interfacial chemical characteristics that influence device fabrication. In this study, octadecyltriethoxysilane (OTES) treatments of thin film ZnO produced by sol-gel decomposition were explored. The ZnO films were hydroxylated and then modified using OTES in solution. The condensation reaction of the OTES at the surface was promoted by the addition of a protoamine catalyst. Contact angle and infrared spectroscopy studies confirmed the surface modification and indicated that the coverage of the OTES was submonolayer. The modified ZnO films were reproducible and stable for long periods. The effects of the modification on subsequently spin-cast poly[3-hexylthiophene](P3HT) and on hybrid ZnO/P3HT organic solar cell performance are discussed.

Exciton splitting and carrier transport across the amorphous-silicon/polymer solar cell interface

The authors study exciton splitting at the interface of bilayer hybrid solar cells to better understand the physics controlling organic-inorganic device performance. Hydrogenated amorphous silicon (a-Si:H)∕poly(3-hexylthiophene) (P3HT) and a-Si:H∕poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) solar cells show photoresponse dominated by exciton production in the polymer. The a-Si:H∕P3HT devices are nearly as efficient as titania/P3HT cells. However, the a-Si:H∕MEH-PPV system has much lower photocurrent than a-Si:H∕P3HT, likely due to inefficient hole transfer back to the MEH-PPV after energy transfer from MEH-PPV to a-Si:H.