Solid-state light-emitting electrochemical cells (LECs) with promising features of solution processability, low-voltage operation and compatibility with inert cathode metals have shown great potential in display and lighting applications in recent years. Among the reported emissive materials for LECs, ionic transition metal complexes (iTMCs) have relatively higher electroluminescence (EL) efficiencies due to their phosphorescent property. However, the red iTMCs generally exhibit moderate color saturation and low emission efficiency, limiting their display applications. To improve color saturation and device efficiency of red LECs, efficient quantum dots (QDs) with narrow emission bandwidth are good alternative emissive materials. In this work, efficient and saturated red QD LECs employing iTMC carrier injection layers to provide in situ electrochemical doping are demonstrated. The thicknesses of iTMC and red-QD layers are systematically adjusted to achieve the best carrier balance. In the optimized device, the iTMC carrier injection layer facilitates hole injection into the red-QD layer while electrons are injected from the cathode into the red-QD layer directly since the electron injection barrier is low. The Commission Internationale de I'Eclairage (CIE) coordinates of the EL spectra approach the red standard point of National Television System Committee (NTSC). High external quantum efficiency and current efficiency reaching 9.7% and 16.1 cd A⁻¹, respectively. These results confirm superior carrier balance in such a simple iTMC/QD bilayer device structure. Furthermore, compared with iTMC LECs, less degree of device efficiency roll-off upon increasing device current is observed in QD LECs since a shorter excited-state lifetime of fluorescent QDs reduces the probability of collision exciton quenching. Saturated and efficient red EL with mitigated efficiency roll-off from red-QD LECs employing iTMC carrier injection layers confirms that they are good candidates of saturated light sources for displays.

固态发光电化学电池（LEC）具有解决方案可加工性，低压操作以及与惰性阴极金属的相容性等有希望的特征，近年来在显示和照明应用中显示出巨大的潜力。在已报道的LEC的发光材料中，离子过渡金属配合物（iTMC）由于具有磷光特性而具有相对较高的电致发光（EL）效率。但是，红色iTMC通常表现出中等的色彩饱和度和较低的发射效率，从而限制了其显示应用。为了提高红色LEC的色彩饱和度和器件效率，具有窄发射带宽的有效量子点（QD）是很好的替代发光材料。在这项工作中，采用iTMC载流子注入层的高效饱和红色QD LEC可以提供原位电化学掺杂得到证明。对iTMC和红色QD层的厚度进行了系统调整，以实现最佳的载流子平衡。在优化的器件中，由于电子注入势垒较低，因此iTMC载流子注入层有助于将空穴注入到红色QD层中，而电子直接从阴极注入到红色QD层中。EL光谱的国际照明委员会（CIE）坐标接近国家电视系统委员会（NTSC）的红色标准点。高外部量子效率和电流效率达到9.7％和16.1 cd A ^-1， 分别。这些结果证实了在这种简单的iTMC / QD双层器件结构中优异的载流子平衡。此外，与iTMC LEC相比，在QD LEC中观察到随着器件电流的增加，器件效率下降的程度较小，因为荧光QD的激发态寿命更短，从而降低了碰撞激子猝灭的可能性。使用iTMC载流子注入层的红色QD LEC具有降低的效率衰减的饱和且高效的红色EL证实了它们是显示器饱和光源的良好候选者。