High-efficiency and reduced efficiency roll-off of top-emitting organic light-emitting diodes

Abstract

Top-emitting organic light-emitting diodes (TEOLEDs) have attracted extensive attention for their high brightness and flat-panel display. However, the efficiency roll-off at high brightness is the issue that needs to be resolved for further practical applications using TEOLED devices. Herein, a serial of high-efficiency tandem TEOLED introducing a fullerene/zinc-phthalocyanine organic semiconductor heterojunction as a charge generation layer is demonstrated. With unique photovoltaic properties, the charge generation layer can absorb part of the photons emitted by the emission layer (Ir(ppy)₃) and generate electrons and holes. By optimizing the thickness of the charge generation layer, the pure green electroluminescent TEOLED device manufactured has a high brightness of 156 000 cd/cm² and a maximum current efficiency of 86 cd/A. Importantly, relying on the energy between the photovoltaic and the microcavity effects, only 1.5% of the efficiency roll-off is obtained at 1 000–10 000 cd/cm². Introducing fullerene/zinc-phthalocyanine as the charge-generating layer provides a promising alternative for developing high-efficiency tandem TEOLED devices.

References

[1] JIANGX, CHENH, WUZ, et al.. Efficient thermally activated delayed fluorescence organic light-emitting device based on an exciplex[J]. Optics letters, 2022, 47(22):5873-5876

[2] TANS, JINNAIK, KABER, et al.. Long-persistent luminescence from an exciplex-based organic light-emitting diode[J]. Advanced materials, 2021, 33(23):2008844

[3] WEIY, KANW, ZHANGJ, et al.. Highly efficient non-doped bilayer organic light-emitting diodes based on tri-phenyl phosphine oxide protected iridium complexes[J]. Applied physics letters, 2020, 117(7): 071901

[4] CHOIS, KANGC, BYUNC W, et al.. Thin-film transistor-driven vertically stacked full-color organic light-emitting diodes for high-resolution active-matrix displays[J]. Nature communications, 2020, 11(1): 1-9

[5] ALLEMEIERD, ISENHARTB, DAHALE, et al.. Emergence and control of photonic band structure in stacked OLED microcavities[J]. Nature communications, 2021, 12(1):1-7

[6] ZOUS J, SHENY, XIEF M, et al.. Recent advances in organic light-emitting diodes: toward smart lighting and displays[J]. Materials chemistry frontiers, 2020, 4(3):788-820

[7] MAC, LIUY F, GAOX M, et al.. Enhanced efficiency of organic light-emitting devices by using a directly imprinted nanopillared ultrathin metallic electrode[J]. Optics letters, 2020, 45(17):4879-4882

[8] LEEJ J, LIP, KUNGH T, et al.. Highly efficient top-emission organic light-emitting diode on an oxidized aluminum anode[J]. Journal of applied physics, 2019, 125(14):145501

[9] YUY, CAOC, WUZ, et al.. Improving the color-rendering index of a tandem warm white organic light-emitting device by employing a simple fabrication process[J]. Optics letters, 2019, 44(4): 931-934

[10] ZANGC, LIUS, XUM, et al.. Top-emitting thermally activated delayed fluorescence organic light-emitting devices with weak light-matter coupling[J]. Light: science & applications, 2021, 10(1):1-10

[11] BAEKS Y, KWAKS Y, KIMS T, et al.. Ancillary ligand increases the efficiency of heteroleptic Ir-based triplet emitters in OLED devices[J]. Nature communications, 2020, 11(1):1-7

[12] YUM, WANGG, ZHAOR, et al.. Improved interfacial wetability in Cu/ZnO and its role in ZnO/Cu/ZnO sandwiched transparent electrodes[J]. Journal of materials science & technology, 2020, 37: 123-127

[13] FUNGM, LIY, LIAOL. Tandem organic light-emitting diodes[J]. Advanced materials, 2016, 28(47):10381-10408

[14] MANJ X, HES J, SHIC S, et al.. Optical design of connecting electrodes for tandem organic light-emitting diodes[J]. Optics letters, 2020, 45(13):3561-3564

[15] JIANGY, CUIM, LIS, et al.. Reducing the impact of Auger recombination in quasi-2D perovskite light-emitting diodes[J]. Nature communications, 2021, 12(1):1-10

[16] DE MORAESI R, SCHOLZS, HERMENAUM, et al.. Impact of temperature on the efficiency of organic light emitting diodes[J]. Organic electronics, 2015, 26: 158-163

[17] YANGX, FENGX, XINJ, et al.. High-performance crystalline organic light-emitting diodes based on multi-layer high-quality crystals[J]. Organic electronics, 2019, 64: 236-240

[18] XIEL, ZHUANGJ, CHENX, et al.. 0.7% roll-off for solution-processed blue phosphorescent OLEDs with a novel electron transport material[J]. ACS photonics, 2017, 4(3):449-453

[19] OHISAS, TAKAHASHIT, IGARASHIM, et al.. An indolocarbazole-based thermally activated delayed fluorescence host for solution-processed phosphorescent tandem organic light-emitting devices exhibiting extremely small efficiency roll-off[J]. Advanced functional materials, 2019, 29(16):1808022

[20] KIMI, HAVERINENH M, LIJ, et al.. Enhanced power conversion efficiency of p-i-n type organic solar cells by employing AP-layer of palladium phthalocyanine[J]. Applied physics letters, 2010, 97(20): 246

[21] RIEDELW, WIESNERS, GREINERD, et al.. Hybrid solar cells with ZnO-nanorods and dry processed small molecule absorber[J]. Applied physics letters, 2014, 104(17): 173503

[22] LESSMANNR, HONGZ, SCHOLZS, et al.. Aging of flat heterojunction zinc phthalocyanine/fullerene C₆₀ organic solar cells[J]. Organic electronics, 2010, 11(4): 539-543

[23] GUOQ, SUNH, WANGJ, et al.. Charge generation mechanism of tandem organic light emitting diodes with pentacene/C₇₀ organic heterojunction as the connecting layer[J]. Journal of materials chemistry C, 2016, 4(2):376-382

[24] YUY, WUZ, YUY, et al.. Highly-efficient tandem organic light-emitting device employing bis-4, 6-(3,5-di-3-pyridylphenyl)-2-methylpyrimi-dine doped with cesium azide in charge generation unit[J]. Organic electronics, 2018, 52: 329-334

[25] JUNGS W, KIMK, PARKH, et al.. Patternable semi-transparent cathode using thermal evaporation for OLED display applications[J]. Advanced electronic materials, 2021, 7(4):2001101

[26] HONGK, KIMK, KIMS, et al.. Optical properties of WO₃/Ag/WO₃ multilayer as transparent cathode in top-emitting organic light emitting diodes[J]. The journal of physical chemistry C, 2011, 115(8): 3453-3459

[27] LIS W, YUC H, KOC L, et al.. Cyanopyrimidine-carbazole hybrid host materials for high-efficiency and low-efficiency roll-off TADF OLEDs[J]. ACS applied materials & interfaces, 2018, 10(15):12930-12936

[28] LIH, BIR, CHENT, et al.. Selectively modulating triplet exciton formation in host materials for highly efficient blue electrophosphorescence[J]. ACS applied materials & interfaces, 2016, 8(11):7274-7282

[29] ZHOUN, WANGS, XIAOY, et al.. Double light-emitting layer implementing three-color emission: using DCJTB lightly doping in Alq3 as red-green emitting layer and APEAn1N as blue-green emitting layer[J]. Journal of luminescence, 2018, 196: 40-49

[30] KIMH B, KIMJ J. Diffusion mechanism of exciplexes in organic optoelectronics[J]. Physical review applied, 2020, 13(2):024006

[31] CHENS, ZHAOZ, JIEZ, et al.. A green top-emitting organic light-emitting device with improved luminance and efficiency[J]. Journal of physics D: applied physics, 2006, 39(17): 3738

[32] KIMS K, LAMPANDER, KWONJ H. Electro-optically efficient and thermally stable multilayer semitransparent pristine Ag cathode structure for top-emission organic light-emitting diodes[J]. ACS photonics, 2019, 6(11): 2957-2965

[33] JIW, ZHANGL, GAOR, et al.. Top-emitting white organic light-emitting devices with down-conversion phosphors: theory and experiment[J]. Optics express, 2008, 16(20):15489-15494