From White to Red: Electric-Field Dependent Chromaticity of Light-Emitting Electrochemical Cells based on Archetypal Porphyrins

Weber M, Wittmann J, Burger A, Malcioglu O, Segarra-Marti J, Hirsch A, Coto PB, Bockstedte M, Costa RD (2016)

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2016

Journal

Publisher: Wiley-VCH Verlag

Book Volume: 26

Pages Range: 6737-6750

Journal Issue: 37

DOI: 10.1002/adfm.201602252

Abstract

The differences in the electroluminescence (EL) of red-emitting free-base (H2TPP) and Zn-metalated (ZnTPP) archetypal porphyrins are rationalized in light-emitting electrochemical cells by means of an electric-field dependent effect, leading to whitish and reddish devices, respectively. Although H2TPP shows superior electrochemical and photophysical features compared to ZnTPP, devices prepared with ZnTPP surprisingly stand out with a deep-red EL similar to its photoluminescence (PL), while H2TPP devices feature unexpected whitish EL. Standard arguments such as degradation, device architecture, device mechanism, and changes in the nature of the emitting excited states are discarded. Based on electrochemical impedance spectroscopy and first-principles electronic structure methods, we provide evidence that the EL originates from two H2TPP regioisomers, in which the inner ring H atoms are placed in collinear and vicinal configurations. The combination of their optical features provides an explanation for both the high- and low-energy EL features. Here, the emitting excited state nature is ascribed to the Q bands, since the Soret excited states remain high in energy. This contrasts to what is traditionally postulated in reports focused on H2TPP lighting devices. Hence, this work provides a new explanation for the nature of the high-energy EL band of H2TPP that might inspire future works focused on white-emitting molecular-based devices.

Authors with CRIS profile

Additional Organisation(s)

Involved external institutions

University of Bologna / Università di Bologna Italy (IT)

How to cite

APA:

Weber, M., Wittmann, J., Burger, A., Malcioglu, O., Segarra-Marti, J., Hirsch, A.,... Costa, R.D. (2016). From White to Red: Electric-Field Dependent Chromaticity of Light-Emitting Electrochemical Cells based on Archetypal Porphyrins. Advanced Functional Materials, 26(37), 6737-6750. https://doi.org/10.1002/adfm.201602252

MLA:

Weber, Michael, et al. "From White to Red: Electric-Field Dependent Chromaticity of Light-Emitting Electrochemical Cells based on Archetypal Porphyrins." Advanced Functional Materials 26.37 (2016): 6737-6750.

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