An amorphous Se0.80S0.20 alloy produced by Mechanical Alloying was studied by Raman spectroscopy, x-ray diffraction, extended x-ray absorption fine structure (EXAFS) and optical absorption spectroscopy, and also through reverse Monte Carlo simulations of its total structure factor and EXAFS data. Its vibrational modes, optical gap and structural properties as average interatomic distances and average coordination numbers were determined and compared to those found for an amorphous Se0.90S0.10 alloy.The results indicate that coordination numbers, interatomic distances and also the gap energy depend on the sulphur concentration.
The charge carrier mobility is an important parameter that directly affects the performance of organic field‐effect transistors. We use copper phthalocyanine (CuPc)‐based transistors having crosslinked poly(vinyl alcohol) (cr‐PVA) as gate insulator to study the variation of the mobility in CuPc with the distance from the gate insulator interface. By measuring the mobility of the charge carriers flowing along the channel as a function of the minimum thickness of the effective channel near to the transistor source, we demonstrate that the mobility is low near to the interface and shows a maximum at approximately 5 nm from the interface. The mobility dependence on distance from interface can be modified through the inclusion of a poorly conducting thin PEDOT:PSS layer between gate insulator and channel semiconductor, which effectively acts as a gate insulator extension. This procedure is a simple but efficient strategy to improve organic field‐effect transistor performance, positively affecting the transconductance and the mobility, which in the studied devices is increased by a factor 20. The improvement is attributed to the suppression of the deleterious consequences of interface charge traps on transport along the channel and is, in principle, a general approach applicable to other organic field‐effect transistor materials combinations.
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