Molecular imprinted polymer films on RFID tags: a first step towards disposable packaging sensors

Molecular imprinted polymer (MIP) sensors offer a high potential in the development of cheap small-scale disposable biomimetic sensors. Molecular imprinting leads to the formation of inert polymer particles with nanocavities, which can exhibit similar selectivity and specificity to target molecules as antibodies or enzymes. These sensors open up many possible applications in the field of mass-market consumer products such as food packaging sensors. One such application is the detection of histamine in spoiled fish, which causes scombroid poisoning, a common seafood poisoning. This contribution provides one possible solution for easing the use of these sensors in field applications. A screen-printed short-range wireless MIP-based biosensor based upon passive radio frequency identification (RFID) tags was developed as a proof of principle. Histamine molecules binding to an MIP recognition layer induce a dielectric change in the sensor capacitance, resulting in a resonance frequency shift that is transmitted by inductive coupling. This wireless sensor is capable of detecting histamine concentrations as low as 50 nM at a range of a few centimeters. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.status: publishe

Fluorination as an effective tool to increase the open-circuit voltage and charge carrier mobility of organic solar cells based on poly(cyclopenta[2,1-b:3,4-b′]dithiophene-alt-quinoxaline) copolymers

The effect of fluorination on the optoelectronic properties and the polymer : fullerene solar cell characteristics of PCPDTQx-type (poly{4-(2′-ethylhexyl)-4-octyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-alt-2,3-bis[5′-(2′′-ethylhexyl)thiophen-2′-yl]quinoxaline}) low bandgap copolymers is reported. The introduction of fluorine atoms on the quinoxaline constituents is an effective way to lower the HOMO and LUMO energy levels of the alternating copolymers, resulting in an enhanced open-circuit voltage for the devices based on the fluorinated polymers (∼0.1 V per F added). Furthermore, fluorination also improves the charge carrier mobility in the bulk heterojunction blends. Despite the formation of unfavorable photoactive layer morphologies, the best solar cell performance is obtained for the copolymer prepared from the difluorinated quinoxaline monomer, affording a power conversion efficiency of 5.26% under AM 1.5G irradiation, with an open-circuit voltage of 0.83 V, a short-circuit current density of 11.58 mA cm−2 and a fill factor of 55%.\u3cbr/\u3

Fluorination as an effective tool to increase the open-circuit voltage and charge carrier mobility of organic solar cells based on poly(cyclopenta[2,1-b:3,4-b′]dithiophene-alt-quinoxaline) copolymers

The effect of fluorination on the optoelectronic properties and the polymer : fullerene solar cell characteristics of PCPDTQx-type (poly{4-(2′-ethylhexyl)-4-octyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-alt-2,3-bis[5′-(2′′-ethylhexyl)thiophen-2′-yl]quinoxaline}) low bandgap copolymers is reported. The introduction of fluorine atoms on the quinoxaline constituents is an effective way to lower the HOMO and LUMO energy levels of the alternating copolymers, resulting in an enhanced open-circuit voltage for the devices based on the fluorinated polymers (∼0.1 V per F added). Furthermore, fluorination also improves the charge carrier mobility in the bulk heterojunction blends. Despite the formation of unfavorable photoactive layer morphologies, the best solar cell performance is obtained for the copolymer prepared from the difluorinated quinoxaline monomer, affording a power conversion efficiency of 5.26% under AM 1.5G irradiation, with an open-circuit voltage of 0.83 V, a short-circuit current density of 11.58 mA cm−2 and a fill factor of 55%

Designing small molecule organic solar cells with high open-circuit voltage

Three extended 2,5-dithienylthiazolo[5,4-d]thiazole-based small molecule chromophores are prepared via a sustainable direct arylation approach and their physicochemical and opto-electrical material characteristics are analyzed toward integration in solution-processed bulk heterojunction organic photovoltaics. Efficient charge separation and high values of the charge transfer state energy are derived from sensitive ground and excited state absorption and photoluminescence measurements on blends of the thiazolo[5,4-d]thiazole-based electron donor components with the PC71BM fullerene acceptor. Upon implementation in organic solar cells, a maximum power conversion efficiency of 2.7% and particularly high open-circuit voltages (0.93−0.98 V) are observed, which are correlated to the charge transfer state energies as derived from photoluminescence, Fourier transform photocurrent spectroscopy and combined electrochemical and photophysical data. Furthermore, several loss processes at the origin of the modest short-circuit current densities and fill factors are elucidated

Oxygen-Induced Degradation in C₆₀-Based Organic Solar Cells: Relation Between Film Properties and Device Performance

Fullerene-based molecules are the archetypical electron-accepting materials for organic photovoltaic devices. A detailed knowledge of the degradation mechanisms that occur in C₆₀ layers will aid in the development of more stable organic solar cells. Here, the impact of storage in air on the optical and electrical properties of C₆₀ is studied in thin films and in devices. Atmospheric exposure induces oxygen-trap states that are 0.19 eV below the LUMO of the fullerene C₆₀. Moreover, oxygen causes a 4-fold decrease of the exciton lifetime in C₆₀ layers, resulting in a 40% drop of short-circuit current from optimized planar heterojunction solar cells. The presence of oxygen-trap states increases the saturation current of the device, resulting in a 20% loss of open-circuit voltage. Design guidelines are outlined to improve air stability for fullerene-containing devices