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We report efficient phosphorescent hybrid organic-inorganic light emitting devices using poly(ethylenimine) as electron-injection layer and interfacial modifier for metal oxides and solution-processed small molecule emissive layers. As a first step, the hole transport layers with various HOMO levels and the hole mobility values including TAPC, TCTA and mCP are evaluated. The results indicate that devices using a TAPC layer show the best luminance and power efficiencies. Subsequently, the optimum phosphor concentration is determined to be ca. 5%. Enlarged efficiency roll-off with increasing current density is observed in devices using the phosphor concentration above the optimum value. We also investigate the morphologies of films having different phosphor concentrations on the top of bare or PEIE-covered glass substrates, which is closely related to device performance. All the films have the RMS values of ca. 1 nm, indicating high-quality solution processed small molecule films. The blue, yellow and red devices show the maximum external quantum efficiencies of 17.3%, 10.7% and 7.3%, respectively. These efficiencies are 17.0%, 10.6% and 5.8% at 1000 cd·m-2, only showing a small roll-off, which can be attributed to alleviated triplet-triplet and triplet-polaron interactions in a broad carrier recombination zone due to using the mixed hole-transport and electron-transport materials as the co-hosts. In addition, these devices exhibit the respective Commission International Eclairage (CIE) coordinates of (0.16, 0.36), (0.50, 0.49) and (0.66, 0.32), which almost traverse the whole visible light region. Furthermore, the hybrid two-colored white devices show a luminance efficiency of 31 cd·A-1, power efficiency of 14.8 lm·W-1 at 1000 cd·m-2 and the operating current-insensitive CIE coordinates of (0.32, 0.42). The efficiencies represent the significant improvement over the previously reported values, which can be attributed to high-quality small molecule films on PEIE, and in particular to the unique properties of small molecule host materials such as balanced carrier transport and high triplet energy. Further efforts including selection of high-mobility electron transport host material and phosphors with high luminescence quantum yield are made to increase the efficiency and reliability of hybrid organic-inorganic light emitting device.
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Keywords:
- hybrid organic-inorganic light emitting devices /
- electrophosphorescence /
- solution processing method /
- white devices
[1] Sessolo M, Bolink H J 2011 Adv. Mater. 23 1829
[2] Huang J Z, Li S S, Feng X P 2010 Acta Phys. Sin. 59 5480 (in Chinese) [黄金昭, 李世帅, 冯秀鹏 2010 59 5480]
[3] Zhang K, Zhong C M, Liu S J, Liang A H, Dong S, Huang F 2014 J. Mater. Chem. C 2 3270
[4] Brine H, Juan F, Bolink H J 2013 Org. Electron. 14 164
[5] Bolink H J, Coronado E, Repetto D, Sessolo M, Barea E M, Bisquert J, Garcia-Belmonte G, Prochazka J, Kavan L 2008 Adv. Funct. Mater. 18 145
[6] Chen J S, Shi C S, Fu Q, Zhao F C, Hu Y, Feng Y L, Ma D G 2012 J. Mater. Chem. 22 5164
[7] Morii K, Ishida M, Takashima T 2006 Appl. Phys. Lett. 89 183510
[8] Lu L P, Kabra D, Friend R H 2012 Adv. Funct. Mater. 22 4165
[9] Bolink H J, Coronado E, Orozco J, Sessolo M 2009 Adv. Mater. 21 79
[10] Bolink H J, Brine H, Coronado E 2010 Adv. Mater. 22 2198
[11] Lu L P, Kabra D, Johnson K, Friend R H 2012 Adv. Funct. Mater. 22 144
[12] Bolink H J, Brine H, Coronado E 2010 ACS Appl. Mater. Interfaces 2 2694
[13] Bolink H J, Coronado E, Sessolo M 2009 Chem. Mater. 21 439
[14] Yook K S, Lee J Y 2014 Adv. Mater. 26 4218
[15] Zhou Y, Fuentes-Hernandez C, Shim J, Meyer J, Giordano A J, Li H, Winget P, Papadopoulos T, Cheun H, Kim J, Fenoll M, Dindar A, Haske W, Najafabadi E, Khan T M, Sojoudi H, Barlow S, Graham S, Brédas J L, Marder S R, Kahn A, Kippelen B 2012 Science 336 327
[16] Yang X H, Wang R X, Fan C J, Li G Q, Xiong Z H, Jabbour G E 2014 Org. Electron. 15 2387
[17] Kim Y H, Han T H, Cho H, Min S Y, Lee C L, Lee T W 2014 Adv. Funct. Mater. 24 3808
[18] Liu J, Shi X D, Wu X K 2014 Org. Electron. 15 2492
[19] Fu Q, Chen J S, Shi C S, Ma D G 2012 ACS Appl. Mater. Interfaces 4 6579
[20] Sun Y M, Seo J H, Takacs C J, Seifter J, Heeger A J 2011 Adv. Mater. 23 1679
[21] Tsuboi T, Liu S W, Wu M F, Chen C T 2009 Org. Electron. 10 1372
[22] Chang Y T, Chang J K, Lee Y T, Wang P S, Wu J L, Hsu C C, Wu I W, Tseng W H, Pi T W, Chen C T, Wu C I 2013 ACS Appl. Mater. Interfaces. 5 10614
[23] Lu M T, Bruyn P D, Nicolai H T, Wetzelaer G J A H, Blom P W M 2012 Org. Electron 13 1693
[24] Lamansky S, Djurovich P, Murphy D 2001 J. Am. Chem. Soc. 123 4304
[25] Walikewitz B H, Kabra D, Gélinas S, Friend R H 2012 Phys. Rev. B 85 045209
[26] Baldo M A, Adachi C, Forrest S R 2001 Phys. Rev. B 62 10967
[27] Reineke S, Walzer K, Leo K 2007 Phys. Rev. B 75 125328
[28] Duan L, Hou L D, Lee T W, Qiao J A, Zhang D Q, Dong G F, Wang L D, Qiu Y 2010 J. Mater. Chem. 20 6392
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[1] Sessolo M, Bolink H J 2011 Adv. Mater. 23 1829
[2] Huang J Z, Li S S, Feng X P 2010 Acta Phys. Sin. 59 5480 (in Chinese) [黄金昭, 李世帅, 冯秀鹏 2010 59 5480]
[3] Zhang K, Zhong C M, Liu S J, Liang A H, Dong S, Huang F 2014 J. Mater. Chem. C 2 3270
[4] Brine H, Juan F, Bolink H J 2013 Org. Electron. 14 164
[5] Bolink H J, Coronado E, Repetto D, Sessolo M, Barea E M, Bisquert J, Garcia-Belmonte G, Prochazka J, Kavan L 2008 Adv. Funct. Mater. 18 145
[6] Chen J S, Shi C S, Fu Q, Zhao F C, Hu Y, Feng Y L, Ma D G 2012 J. Mater. Chem. 22 5164
[7] Morii K, Ishida M, Takashima T 2006 Appl. Phys. Lett. 89 183510
[8] Lu L P, Kabra D, Friend R H 2012 Adv. Funct. Mater. 22 4165
[9] Bolink H J, Coronado E, Orozco J, Sessolo M 2009 Adv. Mater. 21 79
[10] Bolink H J, Brine H, Coronado E 2010 Adv. Mater. 22 2198
[11] Lu L P, Kabra D, Johnson K, Friend R H 2012 Adv. Funct. Mater. 22 144
[12] Bolink H J, Brine H, Coronado E 2010 ACS Appl. Mater. Interfaces 2 2694
[13] Bolink H J, Coronado E, Sessolo M 2009 Chem. Mater. 21 439
[14] Yook K S, Lee J Y 2014 Adv. Mater. 26 4218
[15] Zhou Y, Fuentes-Hernandez C, Shim J, Meyer J, Giordano A J, Li H, Winget P, Papadopoulos T, Cheun H, Kim J, Fenoll M, Dindar A, Haske W, Najafabadi E, Khan T M, Sojoudi H, Barlow S, Graham S, Brédas J L, Marder S R, Kahn A, Kippelen B 2012 Science 336 327
[16] Yang X H, Wang R X, Fan C J, Li G Q, Xiong Z H, Jabbour G E 2014 Org. Electron. 15 2387
[17] Kim Y H, Han T H, Cho H, Min S Y, Lee C L, Lee T W 2014 Adv. Funct. Mater. 24 3808
[18] Liu J, Shi X D, Wu X K 2014 Org. Electron. 15 2492
[19] Fu Q, Chen J S, Shi C S, Ma D G 2012 ACS Appl. Mater. Interfaces 4 6579
[20] Sun Y M, Seo J H, Takacs C J, Seifter J, Heeger A J 2011 Adv. Mater. 23 1679
[21] Tsuboi T, Liu S W, Wu M F, Chen C T 2009 Org. Electron. 10 1372
[22] Chang Y T, Chang J K, Lee Y T, Wang P S, Wu J L, Hsu C C, Wu I W, Tseng W H, Pi T W, Chen C T, Wu C I 2013 ACS Appl. Mater. Interfaces. 5 10614
[23] Lu M T, Bruyn P D, Nicolai H T, Wetzelaer G J A H, Blom P W M 2012 Org. Electron 13 1693
[24] Lamansky S, Djurovich P, Murphy D 2001 J. Am. Chem. Soc. 123 4304
[25] Walikewitz B H, Kabra D, Gélinas S, Friend R H 2012 Phys. Rev. B 85 045209
[26] Baldo M A, Adachi C, Forrest S R 2001 Phys. Rev. B 62 10967
[27] Reineke S, Walzer K, Leo K 2007 Phys. Rev. B 75 125328
[28] Duan L, Hou L D, Lee T W, Qiao J A, Zhang D Q, Dong G F, Wang L D, Qiu Y 2010 J. Mater. Chem. 20 6392
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