Hot-injection has become the most widespread method used for the synthesis of perovskite quantum dots (QDs) with enormous interest for application in optoelectronic devices. However, there are some aspects of the chemistry involved in this synthesis that have not been completely investigated. In this work, we synthesized ultra-high stable CsPbI₃ QDs for more than 15 months by controlling two main parameters: synthesis temperature and the concentration of capping ligands. By increasing the capping ligand concentration during the QD synthesis, we were able to grow CsPbI₃ in a broad range of temperatures, improving the photophysical properties of QDs by increasing the synthesis temperature. We achieved the maximum photoluminescence quantum yield (PLQY) of 93% for a synthesis conducted at 185 °C, establishing an efficient surface passivation to decrease the density of non-radiative recombination sites. Under these optimized synthesis conditions, deep red LEDs with an External Quantum Efficiency (EQE) higher than 6% were achieved. The performance of these LEDs is higher than that of the reported CsPbI₃ QD-LEDs containing standard capping agents, without additional elements or further element exchange. We show that it is possible to produce stable CsPbI₃ QDs with high PLQY and red emission beyond the requirement of the Rec. 2020 standards for red color.

Current efforts to reduce the density of structural defects such as surface passivation, doping, and modified synthetic protocols have allowed us to grow high-quality perovskite nanocrystals (PNCs). However, the role of the purity of the precursors involved during the PNC synthesis to hinder the emergence of defects has not been widely explored. In this work, we analyzed the use of different crystallization processes of PbX₂ (X = Cl^– or I^–) to purify the chemicals and produce highly luminescent and stable CsPbCl_3–xBr_x and CsPbI₃ PNCs. The use of a hydrothermal (Hyd) process to improve the quality of the as-prepared PbCl₂ provides blue-emitting PNCs with efficient ligand surface passivation, a maximum photoluminescence quantum yield (PLQY) of ∼ 88%, and improved photocatalytic activity to oxidize benzyl alcohol, yielding 40%. Then, the hot recrystallization of PbI₂ prior to Hyd treatment led to the formation of red-emissive PNCs with a PLQY of up to 100%, long-term stability around 4 months under ambient air, and a relative humidity of 50–60%. Thus, CsPbI₃ light-emitting diodes were fabricated to provide a maximum external quantum efficiency of up to 13.6%. We claim that the improvement of the PbX₂ crystallinity offers a suitable stoichiometry in the PNC structure, reducing nonradiative carrier traps and so maximizing the radiative recombination dynamics. This contribution gives an insight into how the manipulation of the PbX₂ precursor is a profitable and potential alternative to synthesize PNCs with improved photophysical features by making use of defect engineering.

Photovoltaics has become one of the emerging alternatives to progressively supply/replace conventional energy sources, considering the potential exploitation of solar energy. Depending on the nature of the light harvester to influence on its light-absorption capability and the facility to produce electricity, different generations of solar devices have been fabricated. Early studies of organic molecules (dye sensitizers) with good absorption coefficients, going through metal chalcogenides and, lastly, the timely emergence of halide perovskites, have promoted the development of novel and low-cost solar cells with promising photoconversion efficiency (PCE), close to the well-established Si-based devices. However, main drawbacks such as the degradation/photocorrosion of the active layer, the existence of intrinsic defect sites, and the inherent toxicity of the material due to the presence of some harmful elements have blocked the future commercialization of the above kind of solar cells. In this review, we highlight the current progress in achieving efficient photomaterials for organic, chalcogenides and halide perovskites-based solar cells with the purpose of achieving high PCE values, some of which are breakthroughs in this research topic, and the diverse approaches used to extend the stability of the active layer and improve the performance of the solar devices.