Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction Diffuser
In this study, various diffusers are applied to highly efficient ultra-thin emission layer (EML) structure-based blue phosphorescent organic light-emitting diodes (PHOLEDs) to improve the electroluminescence (EL) characteristics and viewing angle. To achieve highly efficient blue PHOLEDs, the EL cha...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-08-01
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| Series: | Nanomaterials |
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| Online Access: | https://www.mdpi.com/2079-4991/13/16/2357 |
| _version_ | 1797583610625130496 |
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| author | Shin-Woo Kang Eun-Jeong Bae Young-Wook Park Byeong-Kwon Ju |
| author_facet | Shin-Woo Kang Eun-Jeong Bae Young-Wook Park Byeong-Kwon Ju |
| author_sort | Shin-Woo Kang |
| collection | DOAJ |
| description | In this study, various diffusers are applied to highly efficient ultra-thin emission layer (EML) structure-based blue phosphorescent organic light-emitting diodes (PHOLEDs) to improve the electroluminescence (EL) characteristics and viewing angle. To achieve highly efficient blue PHOLEDs, the EL characteristics of ultra-thin EML PHOLEDs with the various diffusers having different structures of pattern–shape (hemisphere/sphere), size (4~75 μm), distribution (surface/embedded), and packing (close-packed/random) were systematically analyzed. The diffusers showed different enhancements in the overall EL characteristics of efficiencies, viewing angle, and others. The EL characteristics showed apparent dependency on their structure. The external quantum efficiency (EQE) was enhanced mainly by following the orders of pattern, size, and shape. Following the pattern size, the EQE enhancement gradually increased; the largest-sized diffuser with a 75 μm closed-packed hemisphere (diffuser-1) showed a 1.47-fold EQE improvement, which was the highest. Meanwhile, the diffuser with a ~7 μm random embedded sphere with a low density (diffuser 5) showed the lowest 1.02-fold-improved EQE. The reference device with ultra-thin EML structure-based blue PHOLEDs showed a maximum EQE of 16.6%, and the device with diffuser 1 achieved a maximum EQE of 24.3% with a 5.1% wider viewing angle compared to the reference device without a diffuser. For the in-depth analysis, the viewing angle profile of the ultra-thin EML PHOLED device and fluorescent green OLEDs were compared. As a result, the efficiency enhancement characteristics of the diffusers show a difference in the viewing angle profile. Finally, the application of the diffuser successfully demonstrated that the EL efficiency and viewing angle could be selectively improved. Additionally, we found that it was possible to realize a wide viewing angle and achieve considerable EQE enhancement by further investigations using high-density and large-sized embedded structures of light-extraction film. |
| first_indexed | 2024-03-10T23:40:19Z |
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| institution | Directory Open Access Journal |
| issn | 2079-4991 |
| language | English |
| last_indexed | 2024-03-10T23:40:19Z |
| publishDate | 2023-08-01 |
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| record_format | Article |
| series | Nanomaterials |
| spelling | doaj.art-2b06eb990f86499d93b244c5ce4e502f2023-11-19T02:27:54ZengMDPI AGNanomaterials2079-49912023-08-011316235710.3390/nano13162357Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction DiffuserShin-Woo Kang0Eun-Jeong Bae1Young-Wook Park2Byeong-Kwon Ju3Display and Nanosensor Laboratory, Department of Electrical Engineering, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 02841, Republic of KoreaDisplay and Nanosensor Laboratory, Department of Electrical Engineering, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 02841, Republic of KoreaNano and Organic-Electronics Laboratory, Department of Display and Semiconductor Engineering, Sun Moon University, Asan 31460, Republic of KoreaDisplay and Nanosensor Laboratory, Department of Electrical Engineering, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 02841, Republic of KoreaIn this study, various diffusers are applied to highly efficient ultra-thin emission layer (EML) structure-based blue phosphorescent organic light-emitting diodes (PHOLEDs) to improve the electroluminescence (EL) characteristics and viewing angle. To achieve highly efficient blue PHOLEDs, the EL characteristics of ultra-thin EML PHOLEDs with the various diffusers having different structures of pattern–shape (hemisphere/sphere), size (4~75 μm), distribution (surface/embedded), and packing (close-packed/random) were systematically analyzed. The diffusers showed different enhancements in the overall EL characteristics of efficiencies, viewing angle, and others. The EL characteristics showed apparent dependency on their structure. The external quantum efficiency (EQE) was enhanced mainly by following the orders of pattern, size, and shape. Following the pattern size, the EQE enhancement gradually increased; the largest-sized diffuser with a 75 μm closed-packed hemisphere (diffuser-1) showed a 1.47-fold EQE improvement, which was the highest. Meanwhile, the diffuser with a ~7 μm random embedded sphere with a low density (diffuser 5) showed the lowest 1.02-fold-improved EQE. The reference device with ultra-thin EML structure-based blue PHOLEDs showed a maximum EQE of 16.6%, and the device with diffuser 1 achieved a maximum EQE of 24.3% with a 5.1% wider viewing angle compared to the reference device without a diffuser. For the in-depth analysis, the viewing angle profile of the ultra-thin EML PHOLED device and fluorescent green OLEDs were compared. As a result, the efficiency enhancement characteristics of the diffusers show a difference in the viewing angle profile. Finally, the application of the diffuser successfully demonstrated that the EL efficiency and viewing angle could be selectively improved. Additionally, we found that it was possible to realize a wide viewing angle and achieve considerable EQE enhancement by further investigations using high-density and large-sized embedded structures of light-extraction film.https://www.mdpi.com/2079-4991/13/16/2357organic light-emitting diodes (OLEDs)ultra-thin EMLundopedphosphorescentFIrpicblue OLEDs |
| spellingShingle | Shin-Woo Kang Eun-Jeong Bae Young-Wook Park Byeong-Kwon Ju Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction Diffuser Nanomaterials organic light-emitting diodes (OLEDs) ultra-thin EML undoped phosphorescent FIrpic blue OLEDs |
| title | Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction Diffuser |
| title_full | Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction Diffuser |
| title_fullStr | Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction Diffuser |
| title_full_unstemmed | Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction Diffuser |
| title_short | Highly Efficient Ultra-Thin EML Blue PHOLEDs with an External Light-Extraction Diffuser |
| title_sort | highly efficient ultra thin eml blue pholeds with an external light extraction diffuser |
| topic | organic light-emitting diodes (OLEDs) ultra-thin EML undoped phosphorescent FIrpic blue OLEDs |
| url | https://www.mdpi.com/2079-4991/13/16/2357 |
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