{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/309207"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/309207","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"DIRECT REAL-TIME REAL-SPACE IMAGING OF ENERGY TRANSPORT IN ORGANIC SEMI-CONDUCTORS","abstract":"Efficient energy transport and charge separation in organic semi-conductors are of vital importance in natural light harvesting for photosynthesis and have huge implications for designing a new generation of organic optoelectronic devices such as photovoltaics, light emitting diodes, sensors and so on. It has been a long-standing goal to understand the nature and mechanisms behind the movement of photo-excited species after the absorption of a photon in organic materials and across interfaces. In this thesis, we explore the energy transport and charge separation dynamics in two systems: a nanotubular J-aggregate formed from the self-assembly of molecular pseudoisocyanine (PIC), and a lateral heterojunction formed between a perylene diimide (PDI) and pentacene. Through femtosecond transient absorption microscopy (with sub-10 fs temporal and sub-10 nm spatial precision), supplemented by various other experiments and modelling, we show that ultrafast energy transport in the PIC systems can be achieved through strong light-matter coupling to form exciton-polaritons which have transport lengths of up to 250 nm at effective velocities of up to 5x10⁶ ms⁻¹. The formation of exciton-polaritons in robust cavity-free organic semiconductors opens up doors to a new generation of light harvesting devices. We also demonstrate a direct visualisation of ultrafast lateral charge separation and movement at the PDI-pentacene interface. We find that excitons proximal to the interface readily dissociate into free electrons and holes, with the latter injected into pentacene and may diffuse efficiently with a diffusion constant D in excess of 200 cms⁻¹, much larger than reported values for excitons in organic and inorganic semiconductors. The ability to visualise ultrafast charge separation at a junction with nanometre resolution will help to develop a more thorough understanding of the physics that underpins most modern optoelectronic devices.","abstract_html":"Efficient energy transport and charge separation in organic semi-conductors are of vital importance in natural light harvesting for photosynthesis and have huge implications for designing a new generation of organic optoelectronic devices such as photovoltaics, light emitting diodes, sensors and so on. It has been a long-standing goal to understand the nature and mechanisms behind the movement of photo-excited species after the absorption of a photon in organic materials and across interfaces. In this thesis, we explore the energy transport and charge separation dynamics in two systems: a nanotubular J-aggregate formed from the self-assembly of molecular pseudoisocyanine (PIC), and a lateral heterojunction formed between a perylene diimide (PDI) and pentacene. Through femtosecond transient absorption microscopy (with sub-10 fs temporal and sub-10 nm spatial precision), supplemented by various other experiments and modelling, we show that ultrafast energy transport in the PIC systems can be achieved through strong light-matter coupling to form exciton-polaritons which have transport lengths of up to 250 nm at effective velocities of up to 5x10⁶ ms⁻¹. The formation of exciton-polaritons in robust cavity-free organic semiconductors opens up doors to a new generation of light harvesting devices. We also demonstrate a direct visualisation of ultrafast lateral charge separation and movement at the PDI-pentacene interface. We find that excitons proximal to the interface readily dissociate into free electrons and holes, with the latter injected into pentacene and may diffuse efficiently with a diffusion constant D in excess of 200 cms⁻¹, much larger than reported values for excitons in organic and inorganic semiconductors. The ability to visualise ultrafast charge separation at a junction with nanometre resolution will help to develop a more thorough understanding of the physics that underpins most modern optoelectronic devices.","abstract_has_math":false,"creators":["Chen, Yuk Shek"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Rao, Akshay"],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-02-18","date_published":"2020-02-18","updated_at":"2026-07-22T22:24:31Z","subjects":["optoelectronics","transient absorption microscopy","organic semiconductors","energy transport"],"languages":["eng"],"rights":[],"rights_urls":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/dd930beb-a251-4644-8778-97196425be10/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.56305","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Rao, Akshay"]},{"key":"dc:creator","label":"Author","values":["Chen, Yuk Shek"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2020-02-18"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/309207"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["optoelectronics","transient absorption microscopy","organic semiconductors","energy transport"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/dd930beb-a251-4644-8778-97196425be10/download","https://www.rioxx.net/licenses/all-rights-reserved/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["10.17863/CAM.56305"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/fa4f2398-9c2f-4a08-a8f5-3708e302940f/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Efficient energy transport and charge separation in organic semi-conductors are of vital importance in natural light harvesting for photosynthesis and have huge implications for designing a new generation of organic optoelectronic devices such as photovoltaics, light emitting diodes, sensors and so on. It has been a long-standing goal to understand the nature and mechanisms behind the movement of photo-excited species after the absorption of a photon in organic materials and across interfaces. In this thesis, we explore the energy transport and charge separation dynamics in two systems: a nanotubular J-aggregate formed from the self-assembly of molecular pseudoisocyanine (PIC), and a lateral heterojunction formed between a perylene diimide (PDI) and pentacene. Through femtosecond transient absorption microscopy (with sub-10 fs temporal and sub-10 nm spatial precision), supplemented by various other experiments and modelling, we show that ultrafast energy transport in the PIC systems can be achieved through strong light-matter coupling to form exciton-polaritons which have transport lengths of up to 250 nm at effective velocities of up to 5x10⁶ ms⁻¹. The formation of exciton-polaritons in robust cavity-free organic semiconductors opens up doors to a new generation of light harvesting devices. We also demonstrate a direct visualisation of ultrafast lateral charge separation and movement at the PDI-pentacene interface. We find that excitons proximal to the interface readily dissociate into free electrons and holes, with the latter injected into pentacene and may diffuse efficiently with a diffusion constant D in excess of 200 cms⁻¹, much larger than reported values for excitons in organic and inorganic semiconductors. The ability to visualise ultrafast charge separation at a junction with nanometre resolution will help to develop a more thorough understanding of the physics that underpins most modern optoelectronic devices."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["0abfd5dc4460827a73bff7ff93ef3d39","353adac0d1ebdfd65ab16480263c3c87"]},{"key":"dc:title","label":"Title","values":["DIRECT REAL-TIME REAL-SPACE IMAGING OF ENERGY TRANSPORT IN ORGANIC SEMI-CONDUCTORS"]}]}],"canonical_facts":{"dc:contributor.advisor":["Rao, Akshay"],"dc:creator":["Chen, Yuk Shek"],"dc:date.issued":["2020-02-18"],"dc:description.abstract":["Efficient energy transport and charge separation in organic semi-conductors are of vital importance in natural light harvesting for photosynthesis and have huge implications for designing a new generation of organic optoelectronic devices such as photovoltaics, light emitting diodes, sensors and so on. 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The formation of exciton-polaritons in robust cavity-free organic semiconductors opens up doors to a new generation of light harvesting devices. We also demonstrate a direct visualisation of ultrafast lateral charge separation and movement at the PDI-pentacene interface. We find that excitons proximal to the interface readily dissociate into free electrons and holes, with the latter injected into pentacene and may diffuse efficiently with a diffusion constant D in excess of 200 cms⁻¹, much larger than reported values for excitons in organic and inorganic semiconductors. The ability to visualise ultrafast charge separation at a junction with nanometre resolution will help to develop a more thorough understanding of the physics that underpins most modern optoelectronic devices."],"dc:format.checksum.md5":["0abfd5dc4460827a73bff7ff93ef3d39","353adac0d1ebdfd65ab16480263c3c87"],"dc:identifier.doi":["10.17863/CAM.56305"],"dc:identifier.uri":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/fa4f2398-9c2f-4a08-a8f5-3708e302940f/download"],"dc:language":["eng"],"dc:publisher.institution":["University of Cambridge"],"dc:relation.isreferencedby.uri":["https://www.repository.cam.ac.uk/handle/1810/309207"],"dc:rights":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/dd930beb-a251-4644-8778-97196425be10/download","https://www.rioxx.net/licenses/all-rights-reserved/"],"dc:subject":["optoelectronics","transient absorption microscopy","organic semiconductors","energy transport"],"dc:title":["DIRECT REAL-TIME REAL-SPACE IMAGING OF ENERGY TRANSPORT IN ORGANIC SEMI-CONDUCTORS"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-22T22:24:31Z"}