1,4-Dihydropyrrolo[3,2-b]pyrroles as active components for electronic and opto-electronic applications
Creators: name: Cb, Ram Kumar
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 340305
subject: Physical properties of materials
classificationCode: 400909
subject: Photonic and electro-optical devices, sensors and systems (excl. communications)
classificationCode: 401802
subject: Molecular and organic electronics

description: The last decade has ushered in the advent of organic materials as active/passive components in electronic devices. In contrast to traditional inorganic materials, the mechanical flexibility of organic materials can readily result in devices which are stretchable, bendable, and wearable; earning them a sobriquet: Plastic electronics. In this context, conjugated Small Molecules (CSMs), a class of plastic electronics, garnered tremendous attention due to their reliable and reproducible synthetic methodologies, high purity, and light weight as compared to polymer based materials. Most importantly, the molecular structure can be tailored to manipulate the intrinsic electronic and opto-electronic properties. The aim of this PhD work was to develop CSMs based on 1,4-dihydropyrrolo[3,2-b]pyrrole derivatives (DHPPs) as active components for electronic and opto-electronic applications. <br><br>During the course of this scientific journey, a critical literature review exposed several knowledge gaps that needed to be fulfilled for a complete understanding of structure-property-device performance. Upon attempting to address these challenges, smart structural modifications through judicious choice of functional groups was carried out to establish a rationale between molecular framework in a quadrupolar A-π-D-π-A configuration and its influence on the electronic and opto-electronic properties. The electrical switching characteristics of these materials have been evaluated by embedding them in a two-terminal Metal-Insulator-Metal configuration and the results confirm that, the materials can mimic the functions of a Permanent, rewriteable flash and Dynamic-Random Access memories (short term memory), which are expected to fulfil the requirements for low-cost flexible information storage applications. The obtained switching data from the devices as a function of molecular changes were systematically analysed to optimize critical parameters like thickness of the active layer, active area of the device and operating window. Further, the possible mechanism responsible for the observed electrical phenomenon was comprehensively studied and elucidated with appropriate physico-chemical characterizations and theoretical simulations.<br><br>Finally, the opto-electronic characteristic of the material was exploited to construct a broadband photodetector based on a single-component photoactive layer. The devices exhibited broad spectral sensitivity, responsivity and excellent detectivity across 350 to 850 nm. The results and comprehensive analysis provided underscored the precision and reliability of the designed opto-electronic sensor. One of the major goals of this thesis was to develop materials that can operate under ambient conditions without the need for hermetic encapsulation. The endurance and aging tests carried out for the devices comprising of the synthesised derivatives as active materials, confirm the long-term stability under the absence of encapsulation. Further optimizations are expected to offer more consistency and reliability for batch-to-batch performance.<br><br>Overall, this PhD work provided significant insights and established a strong rationale for understanding the relationship between the molecular structure and its influence on the electronic properties and device performance. Moreover, the results discussed highlight the choice of DHPPs as electronic components for designing low-cost high performance electronic devices.