A hybrid solid-liquid polymer photodiode for the bioenvironment

We demonstrate that a prototypical semiconducting polymer, poly[2-methoxy-5-( 2′ -ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) maintains unaltered its optoelectronic properties throughout the various steps for neural preparation. Films of MEH-PPV, after prolonged immersion in water or buffer solution, are characterized by linear and nonlinear optical spectroscopy. Based on this result, we introduce a hybrid solid-liquid photodiode based on MEH-PPV, in which we use culturing media as liquid, ionic cathodes. The hybrid device is proposed as an active interface between living tissue and conducting polymers for cell diagnostic and neural implants

Tattoo-Like Transferable Hole Selective Electrodes for Highly Efficient, Solution-Processed Organic Indoor Photovoltaics

In solution-processed organic photovoltaics the deposition of charge selective interlayers or electrodes on top of the photoactive layer is a well-known critical step, typically involving either surface treatments or addition of surfactants. As a general strategy to overcome such processing issues, here a simple and scalable tattoo-based technique is presented for the direct transfer of selective poly(3,4-ethylenedioxythiophene)/polystyrene-sulfonate (PEDOT:PSS) contacts, previously screen printed on commercial temporary tattoo paper, on top of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) films. The obtained structure works both in sunlight and in artificial low-light indoor conditions. In the latter case, which represents a very interesting application scenario for cost-effective flexible and lightweight photovoltaic chargers, excellent photo-conversion performances, in excess of 7.0 %, are achieved, the best performance reported so far for artificial light conversion with OPV based on the well-known P3HT and PCBM blend. As a proof-of-concept toward real applications, this electrode transfer strategy is adopted to fabricate a 6 cm2 mini-module that in indoor low-light conditions can power a temperature-humidity sensor endowed with an LCD display. These results show that tattoo-like transfer of charge selective electrodes is a promising strategy to simplify the fabrication process flow of organic photovoltaics tailored for low light conditions

Experimental investigation of the mechanical robustness of a commercial module and membrane-printed functional layers for flexible organic solar cells

A coupled mechanical and electrical characterization method to monitor the correlation of organic photovoltaic (OPV) electrode resistance and cell performance upon tensile strain and to verify the cause of deterioration and the effect of OPV performance under tensile stress has been developed. Both a commercial OPV module and ethylene tetrafluoroethylene (ETFE) membrane-printed OPV electrode layers have been tested by applying the method. The encapsulation layer strength has been found to be the mechanical bottleneck of the tested commercial OPV module. The decrease in the transparent electrode conductance has been found to be responsible for cell degradation upon tensile strain, with the threshold tensile strain at approximately 2%. A test results comparison between ETFE- and polyethylene terephthalate (PET)-printed OPV layers demonstrated that ETFE-printed electrodes are less brittle and sensitive to tensile strain owing to the network pattern response of ETFE-printed electrodes. In addition, the adoption of Ag/poly(3,4-ethylenedioxythiophene) (PEDOT) layering can improve the tensile strain threshold to almost double to maintaining 80% of the initial normalized layer conductance through the advantage of its “bridging effect”. Collectively, our results provide valuable information and illustrate a promising future for architectural membrane printed OPV

Control of optical properties through photochromism: a promising approach to photonics

In this work studies on photochromism for optics and photonics are reviewed. The versatility of organic chemistry gives photochromic materials wide opportunities for several applications that range from tunable filters and gratings, to refractive-index modulators for optical fibers and communications, to optical memories and sensors. Moreover, novel results on amplified emission efficient modulation in a conjugated polymer/photochromic system are presented

Photochromic Electret: A New Tool for Light Energy Harvesting

In this paper, a photochromic electret for light energy harvesting is proposed and discussed. Such electret directly converts the photon energy into electric energy thanks to a polarization modulation caused by the photochromic reaction, which leads to a change in dipole moment. Theoretical concepts on which the photochromic electret is based are considered with an estimation of the effectiveness as a function of material properties. Finally, an electret based on a photochromic diarylethene is shown with the photoelectric characterization as a proof of concept device

Photoswitching of the second harmonic generation from poled phenyl-substituted dithienylethene thin films and EFISH measurements

The photoswitching of the second harmonic generation signal of poled phenyl-substituted dithienylethene/polystyrene thin films evidence a different behavior in function by their molecular structure. The three nonzero πXXZ(2), πZXX(2), and πZZZ(2) coefficients of second order susceptibility at 1064 nm have been measured for both isomeric forms of substituted diarylethene in polymer films. The relationship between πXXZ(2), πZXX(2), and πZZZ(2) for symmetrical diarylethene (OMe-OMe and CN-CN) differs from that found for the asymmetrical OMe-CN chromophore, suggesting for the two symmetrically substituted molecules a two-dimensional first hyperpolarizability. The two-dimensional first hyperpolarizability model has been checked by a statistical analysis from the correlation between susceptibility and first hyperpolarizability. Analysis of βxxz, βzxx, and βzzz values confirm for OMe-OMe and CN-CN a two-dimensional charge flow pattern, which is different from the monodimensional OMe-CN. Moreover, the goodness of the our statistical model was confirmed by comparing the βz value measured by the EFISH technique with respect to that calculated from the three components βxxz, βzxx, and βzzz