Geometric, electronic and optical properties of organic charge transfer systems: Photovoltaic blends and donor-acceptor co-crystals

Ashokan, Ajith

Title:

Geometric, electronic and optical properties of organic charge transfer systems: Photovoltaic blends and donor-acceptor co-crystals

dc.contributor.advisor	Brédas, Jean-Luc
dc.contributor.author	Ashokan, Ajith
dc.contributor.committeeMember	Sherrill, David
dc.contributor.committeeMember	Reynolds, John
dc.contributor.committeeMember	Reichmanis, Elsa
dc.contributor.committeeMember	Silva, Carlos
dc.contributor.department	Chemistry and Biochemistry
dc.date.accessioned	2020-05-20T16:59:13Z
dc.date.available	2020-05-20T16:59:13Z
dc.date.created	2020-05
dc.date.issued	2020-04-03
dc.date.submitted	May 2020
dc.date.updated	2020-05-20T16:59:13Z
dc.description.abstract	Over the past two decades, π-conjugated organic molecules have found applications in the active layer of different types of organic electronic devices. To optimize and improve the performance of each of these devices, it is important to establish clear connections between chemical-structure, intermolecular packing and their impact on the electronic and charge transport properties in these systems. In this Thesis, we focus on two-component organic material systems – one acting as a π-electron donor (D) and the other as a π-electron acceptor (A) for applications in organic photovoltaics (OPV) and organic field-effect transistors (OFETs). On the OPV side (Chapters 3 & 4), initially, we investigate the solution temperature-dependent aggregation property of a few polymers in their pure phases, which has been recently established as a potential method for morphology control in high-performing OSC devices. We then explore the intermolecular packing properties in the binary blends of polymer and two small molecule acceptors, which in their binary as well as ternary combinations exhibit high power conversion efficiencies. We elucidate clear connections between the molecular scale features that impact the device parameters in both the binary blends. We also obtain useful trends to explain the linear evolution of device parameters in the ternary blends. On the OFET side (Chapters 5 & 6), our focus is on DA charge-transfer co-crystals, which possess potential applications as active layer components in OFET devices. Initially, we investigate the effect of packing on electronic properties of co-crystals based on F6TNAP acceptor and a series of donor molecules. Further, we focus on understanding the evolution in electronic, vibrational and charge-transport properties with sequential addition of alkyl chains on the donor and fluorine atoms on the acceptor on co-crystals based on BTBT-FmTCNQ (m=0, 2, 4) and di-CnBTBT-FmTCNQ (n=8, 12; m=0, 4) series. Finally, we explore the degree of charge-transfer in these systems using an approach based on Mulliken charges. While these results are limited to the systems under consideration, our simulations provide a reliable, molecular-level understanding to systematically improve the morphological characteristics that impact the device performances in organic electronic devices.
dc.description.degree	Ph.D.
dc.format.mimetype	application/pdf
dc.identifier.uri	http://hdl.handle.net/1853/62748
dc.publisher	Georgia Institute of Technology
dc.subject	Morphology
dc.subject	Molecular dynamics simulations
dc.subject	Polymer
dc.subject	Non-fullerene acceptor
dc.subject	DFT calculations
dc.subject	Bandstructure
dc.subject	Co-crystals
dc.title	Geometric, electronic and optical properties of organic charge transfer systems: Photovoltaic blends and donor-acceptor co-crystals
dc.type	Text
dc.type.genre	Dissertation
dspace.entity.type	Publication
local.contributor.advisor	Brédas, Jean-Luc
local.contributor.corporatename	School of Chemistry and Biochemistry
local.contributor.corporatename	College of Sciences
relation.isAdvisorOfPublication	4d846669-7bb3-480a-8267-9b1cd9ff38d2
relation.isOrgUnitOfPublication	f1725b93-3ab8-4c47-a4c3-3596c03d6f1e
relation.isOrgUnitOfPublication	85042be6-2d68-4e07-b384-e1f908fae48a
thesis.degree.level	Doctoral