Vitamin needed: Lanthanides in optoelectronic applications of metal halide perovskites

Metal-halide perovskites-based optoelectronic devices, such as solar cells and light-emitting diodes (LEDs), are transitioning from promising performers to direct competitors to well-established technologies due to the advantage of cost-effectiveness. Perovskite solar cells (PSCs) have achieved power conversion efficiency beyond 25% in less than ten years, showing great potential in low-cost photovoltaics with high efficiency and low fabrication cost. Nanostructured perovskites have yielded world-record LEDs due to their high versatility in the local management of charge carriers and the close-to-unit photoluminescence quantum yields (PLQY). However, the development of such perovskite optoelectronic devices is still restricted by their narrow light absorption band, low charge carrier mobility, energy level mismatching, and poor stability and lifespan of the devices. Lanthanides have been applied in perovskite optoelectronic devices to minimize the abovementioned short-comings. Herein, we provide a brief review of the history of lanthanide materials in perovskite optoelectronic devices and a detailed discussion of the recent developments in this field. We will focus on the advances in lanthanide-doped downshifting downconversion, upconversion systems, perovskite light-harvesters, and charge transport layers for both PSCs and lanthanides-doped perovskite quantum dots/nanocrystals (QDs/NCs) for photoluminescent devices.