| dc.description.abstract | In recent years, the field of organic electronics has been experiencing a
great expansion, due to several characteristics which candidate it as a main
player in the definition of new markets comprising low-cost, flexible and biocompatible
electronics.
Although many experimental works on the optimization of organic devices
have been performed, a real improvement in performance is subordinate to a
good understanding of the underlying physical phenomena. At this purpose,
computer-based simulations are of great importance for the determination of
suitable high-level models and the identification of limiting factors.
This thesis is focused on the application of state-of-the-art Technology
Computer Aided Design (TCAD) tools to organic electronics, aiming to show
how models peculiar to this field can be integrated into a commercial, massproduction
oriented software and exploited for the analysis and design of novel
devices. In this respect, particular importance is given to Organic Phototransistors
(OPTs) and Organic Photodiodes (OPDs), which rely on Bulk Heterojunction
(BHJ) organic semiconductors in order to enhance the photogeneration
quantum yield.
To study the transport properties of a BHJ, testbed Organic Field-Effect
Transistors (OFETs) are fabricated on Silicon substrates with conventional
techniques, such as spin-coating deposition. The current-voltage characteristics
and impedance curves of the OFETs are described using TCAD simulations.
This analysis shows how the transport of charge is limited by the
presence of electronic traps in the material, which negatively affect the subthreshold
swing and cut-off frequency of the OFET.
These considerations can be directly applied to vertical OPTs. A comparative
modeling study is performed in comparison to a planar OPT with means
of TCAD simulations. Results show that vertical devices can outperform the
planar ones in both electrical and optical characteristics, which confirms vertical
OPT a promising technology due to the advantages of reduced channel
length and large sensitive area.
The TCAD methodology also applies to the design rather than analysis
only. This concept is demonstrated on a novel OPD architecture, in which
a wire-grid polarizer is directly integrated into the device in order to make
the photocurrent sensitive to light polarization. The OPD is studied and optimized
using numerical simulations, stressing the effect of important physical
and geometrical parameters. Consequently, a proof-of-concept of the OPD is
demonstrated and the model is refined. A Monte Carlo approach is also proposed
in order to enhance the semiconductor models used for the simulation
of BHJ materials.
In conclusion, this work describes a complete framework in which organic
electronics models are integrated with state-of-the-art TCAD tools. It is our
opinion this approach will set the basis for a better understanding and design
of organic electronic devices in the near future. [edited by author] | it_IT |
