TY - JOUR A1 - Vollbrecht, Joachim A1 - Brus, Viktor V. T1 - On charge carrier density in organic solar cells obtained via capacitance spectroscopy JF - Advanced electronic materials N2 - The determination of the voltage-dependent density of free charge carriers via capacitance spectroscopy is considered an important step in the analysis of emerging photovoltaic technologies, such as organic and perovskite solar cells. In particular, an intimate knowledge of the density of free charge carriers is required for the determination of crucial parameters such as the effective mobility, charge carrier lifetime, nongeminate recombination coefficients, average extraction times, and competition factors. Hence, it is paramount to verify the validity of the commonly employed approaches to obtain the density of free charge carriers. The advantages, drawbacks, and limitations of the most common approaches are investigated in detail and strategies to mitigate misleading values are explored. To this end, two types of nonfullerene organic solar cells based on a PTB7-Th:ITIC-2F blend and a PM6:Y6 blend, respectively, are used as a case study to assess how subsequent analyses of the nongeminate recombination dynamics depend on the chosen approach to calculate the density of free charge carriers via capacitance spectroscopy. KW - bulk-heterojunction solar cells KW - capacitance spectroscopy KW - charge KW - carrier density KW - impedance spectroscopy KW - organic photovoltaics Y1 - 2020 U6 - https://doi.org/10.1002/aelm.202000517 SN - 2199-160X VL - 6 IS - 10 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Vergani, Marco A1 - Carminati, Marco A1 - Ferrari, Giorgio A1 - Landini, Ettore A1 - Caviglia, Claudia A1 - Heiskanen, Arto A1 - Comminges, Clement A1 - Zor, Kinga A1 - Sabourin, David A1 - Dufva, Martin A1 - Dimaki, Maria A1 - Raiteri, Roberto A1 - Wollenberger, Ursula A1 - Emneus, Jenny A1 - Sampietro, Marco T1 - Multichannel bipotentiostat integrated with a microfluidic platform for electrochemical real-time monitoring of cell cultures JF - IEEE Transactions on biomedical circuits and systems N2 - An electrochemical detection system specifically designed for multi-parameter real-time monitoring of stem cell culturing/differentiation in a microfluidic system is presented. It is composed of a very compact 24-channel electronic board, compatible with arrays of microelectrodes and coupled to a microfluidic cell culture system. A versatile data acquisition software enables performing amperometry, cyclic voltammetry and impedance spectroscopy in each of the 12 independent chambers over a 100 kHz bandwidth with current resolution down to 5 pA for 100 ms measuring time. The design of the platform, its realization and experimental characterization are reported, with emphasis on the analysis of impact of input capacitance (i.e., microelectrode size) and microfluidic pump operation on current noise. Programmable sequences of successive injections of analytes (ferricyanide and dopamine) and rinsing buffer solution as well as the impedimetric continuous tracking for seven days of the proliferation of a colony of PC12 cells are successfully demonstrated. KW - Electrochemical measurements KW - impedance spectroscopy KW - microfluidics KW - multichannel potentiostat KW - stem cell monitoring Y1 - 2012 U6 - https://doi.org/10.1109/TBCAS.2012.2187783 SN - 1932-4545 VL - 6 IS - 5 SP - 498 EP - 507 PB - Inst. of Electr. and Electronics Engineers CY - Piscataway ER - TY - JOUR A1 - Wagner, Tom A1 - Lazar, Jaroslav A1 - Schnakenberg, Uwe A1 - Böker, Alexander T1 - In situ Electrothemical Impedance Spectroscopy of Electrostatically Driven Selective Gold Nanoparticle Adsorption on Block Copolymer Lamellae JF - Trials N2 - Electrostatic attraction between charged nano particles and oppositely charged nanopatterned polymeric films enables tailored structuring of functional nanoscopic surfaces. The bottom-up fabrication of organic/inorganic composites for example bears promising potential toward cheap fabrication of catalysts, optical sensors, and the manufacture of miniaturized electric circuitry. However, only little is known about the time-dependent adsorption behavior and the electronic or ionic charge transfer in the film bulk and at interfaces during nanoparticle assembly via electrostatic interactions. In situ electrochemical impedance spectroscopy (EIS) in combination with a microfluidic system for fast and reproducible liquid delivery was thus applied to monitor the selective deposition of negatively charged gold nanoparticles on top of positively charged poly(2-vinylpyridinium) (qP2VP) domains of phase separated lamellar poly(styrene)-block-poly(2-vinylpyridinium) (PS-b-qP2VP) diblock copolymer thin films. The acquired impedance data delivered information with respect to interfacial charge alteration, ionic diffusion, and the charge dependent nanoparticle adsorption kinetics, considering this yet unexplored system. We demonstrate that the selective adsorption of negatively charged gold nanoparticles (AuNPs) on positively charged qP2VP domains of lamellar PS-b-qP2VP thin films can indeed be tracked by EIS. Moreover, we show that the nanoparticle adsorption kinetics and the nanoparticle packing density are functions of the charge density in the qP2VP domains. KW - impedance spectroscopy KW - block copolymers KW - nanoparticles KW - electrostatics KW - adsorption kinetics Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b07708 SN - 1944-8244 VL - 8 SP - 27282 EP - 27290 PB - American Chemical Society CY - Washington ER -