Visible light-emitting host-guest electrochemical cells using cyanine dyes

Abstract

Light-emitting electrochemical cells (LECs) can be fabricated as a single emissive organic/salt layer sandwiched between two electrodes, offering cost-effective next generation signage and lighting applications. Cyanine dyes are especially attractive to exploit the low cost potential of LECs. Cyanines denote a large class of fluorescent organic salts with tuneable emission wavelength, inherent conductivity for ionic and electronic charges, and many cyanines are commercially available at low cost. We systematically tested a set of cyanine dyes for visible emitting LECs. To circumvent non-radiative quenching processes in pure cyanine films (monomer fluorescence quantum yields, PLQE, < 1.5%) we exploited the efficient resonance energy transfer (RET) from cyanine host to cyanine guest molecules (PLQE maximum = 16.2%). The analysis indicated that specific host-guest interactions or a parallel energy transfer channel to host dimers can reduce the guest PLQE, despite a generally high RET efficiency in cyanine host-guest systems. By comparing single component with host-guest LECs, we found that the PLQE enhancement directly translated into the device efficiency increase, and red-emitting host-guest LECs with an external quantum efficiency (EQE) of 0.36% were achieved, close to the theoretical EQE maximum (0.81%). Chemical approaches that provide sterically demanding (to increase the PLQE) and high bandgap (for emission at smaller wavelengths) cyanines at low cost promise further progress in the field.

The Dynamic Emission Zone in Sandwich Polymer Light‐Emitting Electrochemical Cells

“…Next to polymers, ionic transition metal complexes (iTCMs) and organic salts have been used as active LEC materials. [7,[11][12][13] For these materials, the ionic and electronic transport occurs in the same material, but the device operation mechanism can be described by the same underlying processes. [14,15] The developing p-i-n junction and the position of the zone where light is emitted (emission zone, EZ) can conveniently be followed by optical probing and photoluminescence experiments on so-called planar LECs that have a wide horizontal gap between the two electrodes.…”

Recent Progress on Light‐Emitting Electrochemical Cells with Nonpolymeric Materials

“…This could offer further simplicity and applicability of a variety of materials. In this section, we highlight current advances in ionic-material LECs, namely, iTMCs, [31, iSMs, [97][98][99][100][101][102][103][104][105][106][107][108][109] and perovskite LECs, [113][114][115][116][117][118] in terms of luminance efficiency, device lifetime, and recent approaches for future applications.…”

Exploiting supramolecular assemblies for filterless ultra-narrowband organic photodetectors with inkjet fabrication capability

“…This can be due to counterion migration in the active layer, which can form a space-charge layer, thereby influencing the response time of the detector. 69 The -3dB frequency values without pre-conditioning are summarized in Table 1 and were used to calculate NEP and specific detectivity D*. "-" means not mentioned…”