P. Morvillo

Nanostructured porous silicon for gas sensor applications

Abstract The response of two different types of nanostructured gas sensor to oxygen has been investigated. The first (optical) is based on the photoluminescence quenching effect of a porous silicon sample, the second on the changes of the electrical conductance v. environment of a porous silicon free standing membrane on an insulating neutral substrate. The response of both the devices to oxygen have been measured and compared. The optical based gas sensor exhibits a quenching following the Stern-Volmer model. The corresponding reactivity rate constant is found to depend on a characteristic nanodimension of the wire. The electrically operated sensor is more sensitive to oxygen and shows an opposite behavior if exposed to a reducing environment.

The Influence of the Fullerene on the Optical Constants of the Photoactive Blend Film of a Polymer Solar Cell

The short circuit current density (Jsc) of polymer solar cells is strictly related to the absorption of the blend film. Recently it has been shown that the use of [70]PCBM as electron acceptor can improve the current output of such devices because C70 derivatives have a stronger and broader absorption compared to C60 ones. The aim of this work is to study the influence of the fullerene on the optical behaviour of the photoactive blend film of a polymer solar cell. We have determined the optical constants of a P3HT:[70]PCBM blend film and studied their variation as a function of the annealing temperature. Afterward, we simulated the optical absorption of the active layer inside the device structure and calculated the maximum achievable Jsc with the aim to correlate the variation of the optical constants to the device output current. We compared this value with that one obtained using a P3HT:[60]PCBM blend.

Bisadducts of C70 as Electron Acceptors for Bulk Heterojunction Solar Cells: A Theoretical Study

In the present study, we have used density functional molecular orbital calculations to investigate the energy levels of the frontier orbitals of novel bisadducts of Phenyl-C71-Butyric-Acid-Methyl Ester (bis[70]PCBM) in an attempt to verify if they can be used as electron acceptor in polymer-fullerene solar cells. C70 derivatives are promising materials for these devices because they have a stronger and broader absorption compared to C60 ones, and they can improve the current output of the corresponding polymer-fullerene solar cells. The calculated LUMO levels for the bis[70]PCBM isomers are higher compared to the monoadduct already used as acceptor in such devices. Since the open circuit voltage (Voc) for devices with ohmic contacts is proportional to the difference between the HOMO of the donor polymer and the LUMO of the acceptor, these bisadducts can increase the Voc of polymer solar cells having poly(3-hexylthiophene) as donor.

Selective inclusion of chromophore molecules into poly(styrene- b -methylmethacrylate) block copolymer nanodomains: a study of morphological, optical and electrical properties

Innovative nanocomposites based on a nanostructured block copolymer (BCP) matrix whose lamellar nanodomains are selectively loaded with organic molecules, were prepared. A symmetric poly(styrene-b-methylmethacrylate) (PS-b-PMMA) amorphous BCP showing a lamellar morphology was employed. Thin films of PS-b-PMMA were deposited by spin-coating on indium thin oxide (ITO) substrate in order to achieve orientation of lamellae with the lamellar surface perpendicular to the substrate. Nanocomposites were then prepared by selective incorporation of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) molecules into the PS lamellar domain. The self-assembly of the BCP generated the nanotemplate to selectively control the spatial location of the PCBM molecules, in which the apolar properties of PS block provided the physical stabilization for achieving uniform PCBM distribution. These innovative approaches can be utilized as a tool to realize memory devices.

Highly conductive PEDOT:PSS on flexible substrate as ITO-free anode for polymer solar cells

In this work, highly conductive anode based on PEDOT:PSS is proposed as substitute of Indio-Tin Oxide (ITO) in flexible solar cells. The anodic conductive polymer was spin coated on a 125 μm thick polyethylene naphthalate (PEN) substrate. The obtained film was characterized in terms of structure and physical- chemical proprieties. The obtained results are very promising and the conductive film will be investigated in future as electrode in a complete polymeric solar cell.

ITO-free polymer solar cells with inkjet-printed highly-conductive PEDOT:PSS anode

Actually the most promising polymer solar cell architecture utilizes ITO as transparent conductve anodic electrode. The limited flexibility of ITO and the increasing cost of indium make this kind of electrode not desirable for realizations of low-cost and flexible solar cells. For this reason, it is necessary to develop low-cost, highly flexible and transparent electrodes that can replace the widely used ITO. In this paper, we investigated a new commercial dispersion of PEDOT:PSS suitably modified with dimethyl sulfoxide in solution in order to obtain a highly transparent and conductive manufactured film (HC-PEDOT:PSS) by inkjet printing.