Elucidation of hole transport mechanism in efficient energy cascade organic photovoltaics using triple donor system

Jung, Kyu Sik; Park, Soo Hyung; Yoo, Je-Hyun; Jung, Na Eun; Moon, Byung Joon; Lee, Sang Hyun; Yi, Yeonjin; Lee, Hyunbok

doi:10.1016/j.apsusc.2021.151747

Cited by 6 publications

(1 citation statement)

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“…At thicknesses of 2 nm and 5 nm, the work functions were 4.80 eV and 4.50 eV, respectively. These changes in the work function, from increasing to decreasing with respect to the film thickness, might be attributable to factors such as charge transfer, interface states, dipole orientation, and other related phenomena [39][40][41]. However, the exact origin cannot be resolved at present, and further research is required.…”

Section: Resultsmentioning

confidence: 99%

Effects of HAT-CN Layer Thickness on Molecular Orientation and Energy-Level Alignment with ZnPc

Joo

Hur

et al. 2023

Molecules

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Efficient energy-level alignment is crucial for achieving high performance in organic electronic devices. Because the electronic structure of an organic semiconductor is significantly influenced by its molecular orientation, comprehensively understanding the molecular orientation and electronic structure of the organic layer is essential. In this study, we investigated the interface between a 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) hole injection layer and a zinc-phthalocyanine (ZnPc) p-type organic semiconductor. To determine the energy-level alignment and molecular orientation, we conducted in situ ultraviolet and X-ray photoelectron spectroscopies, as well as angle-resolved X-ray absorption spectroscopy. We found that the HAT-CN molecules were oriented relatively face-on (40°) in the thin (5 nm) layer, whereas they were oriented relatively edge-on (62°) in the thick (100 nm) layer. By contrast, ZnPc orientation was not significantly altered by the underlying HAT-CN orientation. The highest occupied molecular orbital (HOMO) level of ZnPc was closer to the Fermi level on the 100 nm thick HAT-CN layer than on the 5 nm thick HAT-CN layer because of the higher work function. Consequently, a considerably low energy gap between the lowest unoccupied molecular orbital level of HAT-CN and the HOMO level of ZnPc was formed in the 100 nm thick HAT-CN case. This may improve the hole injection ability of the anode system, which can be utilized in various electronic devices.

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Section: Resultsmentioning

confidence: 99%