N. Lago

Effects of current stress and thermal storage on polymeric heterojunction P3HT:PCBM solar cell

We subjected P3HT:PCBM solar cells to electrical constant current stress and thermal storage. We employed the impedance spectroscopy technique combined to conventional DC measurements for device characterization during all stresses. We identified and separated different contributions affecting the open circuit voltage and short circuit current. Several mechanisms are behind these changes during the stresses; in particular, we underlined the exciton recombination rate and the variation of the built-in voltage.

Effects of constant voltage stress on organic complementary logic inverters

We subjected all-organic complementary inverters to constant voltage stress. We found a 20% maximum variation of DC inverter parameters after a 104-s stress. The largest degradation was in the delay times, which increase up to a factor 7. This is due to the threshold voltage variation in pTFTs and the mobility reduction in nTFTs.

Stress-induced degradation of p- and n-type organic thin-film-transistors in the ON and OFF states

Abstract In this work we analyzed the effect of different stress configurations on p- and n-type organic thin-film-transistors, to emulate the various operating conditions in a real application. Devices showed the largest degradation when they are stressed in the ON condition, because of the uniform charge injection and defect generation in the whole channel area. Charge trapping kinetics and mobility degradation was also strongly dependent on the semiconductor type, suggesting a key-role of the semiconductor on the device reliability.

On the Pulsed and Transient Characterization of Organic Field-Effect Transistors

We performed pulsed measurements on organic transistors presenting four different active materials. All the devices show a strong correlation between the drain-source current and the pulse width. We attributed this phenomenon to the long time needed for channel formation and depletion. These transient effects may have a severe impact on device characterization and application development.

Effects of stair case gate bias stress in IGZO/Al2O3 flexible TFTs

Abstract In this work, we studied the impact of stair-case gate bias stress on flexible Indium-Gallium-Zinc-Oxide Thin-Film Transistors and we estimated the breakdown voltage for different channel aspect ratios. The results show that the breakdown voltage exhibits a remarkable dependence on the channel width, while exposing no or marginal dependence on the channel length. The analysis of the threshold voltage evolution shows that after an initial increase, a remarkable decrease occurs for larger bias, indicating the action of at least two charge trapping phenomena.

Investigation of Mobility Transient on Organic Transistor by Means of DLTS Technique

We analyzed the transient response of organic transistors by means of the deep-level transient spectroscopy technique. We showed how the current transient can be related to a mobility transient from which we estimated two different kinds of activation energies as well as information to the density of states.