Transient Optical and Electrical Phenomena in Organic Semiconductors

Yadu Ram Panthi
Lecture of the lecture cycle
7.3.2024 14:00, Club B

The growing demand for flexible and cost-effective printable optoelectronics devices, including memristors, organic field-effect transistors (OFETs), and organic photovoltaics (OPVs), can be fulfilled employing organic semiconductors (OSCs) comprising -conjugated system. Understanding the photophysics and charge-transport properties relative to molecular structure is crucial for enhancing device functionality and optimizing underlying processes. This presentation will focus on the optical and electrical properties of OSCs outlined in the Doctoral Thesis, showing several intriguing results. To begin, research on thiophene-diketopyrrolopyrrole (TDPP)-based -conjugated small molecules revealed structure-dependent properties in excitonic generation. Effective triplet generation, possibly facilitated by singlet fission, was observed. However, the overlap between the triplet spectrum and differential spectra of temperature-dependent absorption spectra illustrates the possibility that the observed signal assigned to triplets may stem from laser-induced heating. Additionally, study of carbazole-substituted methacrylamide polymer and composite of TDPP-based polymer with perylene demonstrated non-volatile memory capable of data retaining for hours, and exhibiting synapse-mimicking functionalities. Furthermore, the role of mobile dipoles in the high-k dielectric layer in OFETs was investigated. Such dipoles caused a hysteresis in the current-voltage characteristics of the transistor with TIPS-pentacene as an active layer. It was possible to control these effects by thermal crosslinking during the deposition of the dielectric layer and by surface passivation.

The lecture is presented in English