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From a numerically exact solution of the Master equation for hoppingtransport in a disordered energy landscape with a Gaussian densityof states, we determine the dependence on temperature, carrier density, and electric field of the charge carrier mobility. Experimentalspace-charge limited currents in semiconducting polymer-based devices are excellently reproduced with this unified description of the mobility. At room temperature it is mainly the dependence on carrier density that plays an important role, whereas at low temperatures andhigh fields the electric field dependence becomes important. Omission of the carrier-density dependence has led to an underestimation of the hopping distance and the width of the density of states in these polymers.

Nitrogen dioxide (NO2) detection with ZnO field-effect transistors is based on changes in the threshold voltage caused by charge carriertrapping. Here we investigate the dynamics of charge trapping and recovery as a function of temperature. The threshold voltage shifts for both trapping and recovery follow a stretched-exponential time dependence with thermally activated relaxation times. We find an activation energy of 0.1 eV and 1.2 eV for trapping and detrapping, respectively. The attempt-to-escape frequency and characteristic temperature have been determined as 1 Hz and 960 K for charge trapping and 1011 Hz and 750 K for recovery. Thermally stimulated current measurements confirm the presence of trapped charge carriers with a trap depth of around 1 eV. The obtained functional dependence is used as input for an analytical model that predicts the sensors temporal behaviour. The model is experimentally verified and a real-time sensor hasbeen developed. The perfect agreement between predicted and measured sensor response validates the methodology developed. The analytical description can be used to optimize the driving protocol. By adjusting the duration of charging and resetting and the operating temperature, the response time can be optimized and the sensitivity can bemaximized for the desired NO2 pressure window.