Yong Joo Cho, Hyeonghwa Yu, Elizabeth Salsberg, H. Aziz
{"title":"Investigating the root causes of the stability-gap between solution-coated and vacuum-deposited small-molecule organic light-emitting devices (Conference Presentation)","authors":"Yong Joo Cho, Hyeonghwa Yu, Elizabeth Salsberg, H. Aziz","doi":"10.1117/12.2511531","DOIUrl":"https://doi.org/10.1117/12.2511531","url":null,"abstract":"","PeriodicalId":325301,"journal":{"name":"Advances in Display Technologies IX","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131202168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Triplet-triplet annihilation provides a way to generate stable, high energy (blue) emission from organic light-emitting diodes via the fusion of low energy triplet excitons. Low energy sensitizers can be used to populate the triplet states of the emitter, which allows low voltages can be used. However, these same sensitizers can also quench the emission of the high energy singlet in the emitter layer. Managing the motion of triplet excitons by adding a triplet-diffusion-singlet-blocking layer allows us to decouple the sensitization and emission events, preventing singlet quenching and enhancing the blue emission by a factor of 10 or more.
{"title":"Managing triplet excitons to enhance performance of blue OLED materials (Conference Presentation)","authors":"C. Bardeen","doi":"10.1117/12.2513789","DOIUrl":"https://doi.org/10.1117/12.2513789","url":null,"abstract":"Triplet-triplet annihilation provides a way to generate stable, high energy (blue) emission from organic light-emitting diodes via the fusion of low energy triplet excitons. Low energy sensitizers can be used to populate the triplet states of the emitter, which allows low voltages can be used. However, these same sensitizers can also quench the emission of the high energy singlet in the emitter layer. Managing the motion of triplet excitons by adding a triplet-diffusion-singlet-blocking layer allows us to decouple the sensitization and emission events, preventing singlet quenching and enhancing the blue emission by a factor of 10 or more.","PeriodicalId":325301,"journal":{"name":"Advances in Display Technologies IX","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134198319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chia-Hsun Chen, M. Leung, Jiu-Haw Lee, Tien‐Lung Chiu, Chi-feng Lin
Organic light emitting diode (OLED) has lots of advantages in display technology such as self-emissive, light-weight, and compatible for flexible substrates. Compared to the red and green OLEDs, blue one has shorter lifetime due to high-energy polaron quenching. Triplet-triplet annihilation up conversion (TTAUC) is a promising way to reduce the driving voltage and improve the operation lifetime for a blue OLED. This system includes two materials, sensitizer and emitter, which has a narrower bandgap and triplet-triplet annihilation (TTA) characteristic, respectively. When the sensitizer is excited, its triplet exciton can transfer the energy to the triplet of emitter with lower triplet energy and fuse into one singlet exciton with a higher energy photon than the sensitizer. In this research, we demonstrate that a convention green fluorescent material, tris(8-hydroxyquinolinato)aluminum (Alq3) can be used as a sensitizer for a blue TTA emitter, 9,10-Bis(2-naphthyl)anthraces (ADN). In a conventional Alq3-based OLED, when the electron and hole coming from cathode and anode recombined at Alq3 as the recombination layer, 25% of singlet and 75% of triplet were generated. All triplet exciton experienced non-radiative recombination, which resulted in low efficiency due to the poor reverse intersystem crossing (RISC) rate. On the other hand, in TTAUC-OLED, triplet exciton of Alq3 (ET=2.0 eV) transferred the energy to the triplet of ADN (ET=1.67 eV) via Dexter energy transfer and two of them fused into one singlet (ES=2.83 eV) with blue emission. This recycled the useless triplet exciton and resulted in a higher external quantum efficiency (EQE) for TTAUC-OLED (2.1%) compared to the Alq3 (1.2%) and ADN (1.67%) control devices. Moreover, the recombination zone was shifted from ADN to Alq3, the operation lifetime of blue component can be increased by 3x times longer than the ADN control device. From transient electroluminescence (TrEL) measurement, Alq3-control device showed a fast decay within 1us which implied only singlet exciton involved. For the TTAUC-OLED, blue emission showed only delayed component which meant the emission came from only TTA process without direct recombination.
{"title":"Blue organic light-emitting OLED with triplet-triplet fluorescence sensitized by tris(8-hydroxyquinolinato)aluminum (Conference Presentation)","authors":"Chia-Hsun Chen, M. Leung, Jiu-Haw Lee, Tien‐Lung Chiu, Chi-feng Lin","doi":"10.1117/12.2507723","DOIUrl":"https://doi.org/10.1117/12.2507723","url":null,"abstract":"Organic light emitting diode (OLED) has lots of advantages in display technology such as self-emissive, light-weight, and compatible for flexible substrates. Compared to the red and green OLEDs, blue one has shorter lifetime due to high-energy polaron quenching. Triplet-triplet annihilation up conversion (TTAUC) is a promising way to reduce the driving voltage and improve the operation lifetime for a blue OLED. This system includes two materials, sensitizer and emitter, which has a narrower bandgap and triplet-triplet annihilation (TTA) characteristic, respectively. When the sensitizer is excited, its triplet exciton can transfer the energy to the triplet of emitter with lower triplet energy and fuse into one singlet exciton with a higher energy photon than the sensitizer. \u0000In this research, we demonstrate that a convention green fluorescent material, tris(8-hydroxyquinolinato)aluminum (Alq3) can be used as a sensitizer for a blue TTA emitter, 9,10-Bis(2-naphthyl)anthraces (ADN). In a conventional Alq3-based OLED, when the electron and hole coming from cathode and anode recombined at Alq3 as the recombination layer, 25% of singlet and 75% of triplet were generated. All triplet exciton experienced non-radiative recombination, which resulted in low efficiency due to the poor reverse intersystem crossing (RISC) rate. On the other hand, in TTAUC-OLED, triplet exciton of Alq3 (ET=2.0 eV) transferred the energy to the triplet of ADN (ET=1.67 eV) via Dexter energy transfer and two of them fused into one singlet (ES=2.83 eV) with blue emission. This recycled the useless triplet exciton and resulted in a higher external quantum efficiency (EQE) for TTAUC-OLED (2.1%) compared to the Alq3 (1.2%) and ADN (1.67%) control devices. Moreover, the recombination zone was shifted from ADN to Alq3, the operation lifetime of blue component can be increased by 3x times longer than the ADN control device. From transient electroluminescence (TrEL) measurement, Alq3-control device showed a fast decay within 1us which implied only singlet exciton involved. For the TTAUC-OLED, blue emission showed only delayed component which meant the emission came from only TTA process without direct recombination.","PeriodicalId":325301,"journal":{"name":"Advances in Display Technologies IX","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129169657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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