Light-emitting electrochemical cells (LEECs) are thin film light-emitting devices typically consisting of an emissive layer containing ionic species that facilitate charge transport and an emissive semiconductor material. The emissive layer is sandwiched between two air-stable electrodes. Upon application of an external bias the ions in the active layer migrate to the corresponding electrodes, resulting in the formation of electrical double layers (EDLs) at the interface of the electrodes. The EDLs facilitate charge injection into the emissive layer regardless of the energy levels of the electroactive species and work function of the electrodes. Injection of electrons and holes creates oxidized and reduced species near the anode and cathode, respectively. These oxidized and reduced species are stabilized by the ions to form a p-i-n junction in the bulk of the emissive layer and emission takes place within the intrinsic region. Two families of widely investigated emitters for LEECs are ionic transition metal complexes (iTMCs) and conjugated polymers (CPs). From the early use of ruthenium(II) complexes, a significant amount of research has focussed on developing high-performance iTMC-based LEECs, with iridium(III) complexes typically showing the greatest potential. A detracting feature of many iTMC LEECs is the use of scarce noble metal complexes. Despite the enormous number of low molecular weight organic emitters designed for use in organic light-emitting diodes (OLEDs), relatively little attention has been devoted to the design of ionic small molecule (SMs) organic emitters for LEECs. The majority of the reported SM emitters for LEECs are fluorescent in nature and so the internal quantum efficiency (IQE) of the device is limited to 25%. Thermally activated delayed fluorescent (TADF) emitters are one class of purely organic materials that can harvest triplet excitons in electroluminescent (EL) devices through a triplet to singlet reverse intersystem crossing (RISC) upconversion process. Indeed, OLEDs using TADF emitters can achieve up to 100% IQE, comparable to devices using phosphorescent emitters. 15 Purely organic TADF emitters have not been widely investigated for use in LEECs. We reported the first organic TADF LEEC, 2, in 2015 by adapting the structure of the known TADF emitter 2CzPN with imidazolium groups (Figure ). The LEEC devices showed a maximum external quantum efficiency (EQEmax) of 0.39%, a maximum brightness (Bmax) of 13 cd m -2 and a peak electroluminescence (λEL) at 538 nm. The device performance suffered when the emissive layer was doped with an ionic liquid (EQEmax = 0.12%, Bmax = 10 cd m -2 ), which was incorporated to increase charge mobility within the emissive layer. We later showed that this emitter could act as host material in combination with a cyanine dye emitter. The EQEmax for this host-guest device was higher than for the non-doped device, at 2.0% demonstrated 100% exciton utilization efficiency in the device and efficient energy transfer from the host to the guest cyanine emitter. Deep blue emission in LEECs is challenging. We also reported a blue-emitting LEEC employing a cationic sulfone-based donor-acceptor TADF emitter, imCzDPS (λPL = 440 nm, ΦPL = 44%, neat film). The EL of the LEEC was red-shifted at λEL of 470 nm compared to the PL. Following these initial reports Edman and co-workers demonstrated how neutral TADF small molecules, 20 polymers 21 and dendrimers 22 could be employed in LEECs where the emissive layer also contained an inorganic salt and a conducting polymer. Recently, a step-change in device performance were achieved by He et al. who employed a cationic TADF compound that possesses low-lying through-space and through-bond charge transfer excited states. The LEEC showed a green EL with a peak brightness of 572 cd m -2 and an EQEmax of 6.8% at 4.0 V. The half-life of their device reached 218 h at a brightness of 162 cd m -2 . Recently, Su et al. reported two ionic TADF emitters incorporating a pyridinium moiety, Pym-CZ and Pym-tBuCZ as the acceptor and carbazole or tertbutylcarbazole as donor groups. Pym-CZ showed red emission in dichloromethane (λPL= 691 nm, ΦPL = 43%) and in the neat film (λPL= 583 nm, ΦPL = 15%). The emission is further red-shifted and attenuated in Pym-tBuCZ in dichloromethane (λPL= 740 nm, ΦPL = 8%) and in the neat film (λPL= 593 nm, ΦPL = 6%). The LEECs with Pym-CZ (λEL = 599 nm, Bmax = 8.69 cd m -2 , EQEmax = 0.91%) and Pym-tBuCZ (λEL = 618 nm, Bmax = 1.96 cd m -2 , EQEmax = 0.05%) are the first examples of orange-red devices employing purely organic intrinsically ionic TADF emitters. Though these reports hint at the potential of TADF emitters in LEECs, the emission in these devices is typically broad, reflective of the charge transfer (CT) character of the emission, and so color purity suffers.