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Summary With rapid progress in perovskite light-emitting diodes (PeLEDs), the electroluminescence performance of large-area is of increasing interest. We investigated why large-area performance lags behind that achieved in laboratory-scale devices and found that defects in perovskite films—emerging from thermal convection during solvent evaporation, as well as electronic traps formed during perovskite crystallization—are chief causes. Here, we report a molecular modification strategy that simultaneously eliminates pinholes in perovskite layers by controlling the dynamics of film formation and that passivates defects in perovskites by incorporating Br species, thereby preventing shorts and non-radiative recombination. The molecular modifier 1,3,5-tris (bromomethyl) benzene (TBB) also modulates the electronic structure of injection or transport materials to achieve improved charge injection and balanced charge transport. As a result, we demonstrate 20 mm × 20 mm green perovskite nanocrystal LEDs that achieve an external quantum efficiency (EQE) of over 16%, a record for large-area PeLEDs.

The power conversion efficiency (PCE) of tin perovskite solar cells is impeded by the extremely poor resistance to oxidation and high density of intrinsic Sn vacancies. Herein, we grow a 2D-quasi-2D-3D Sn perovskite film using removable pseudohalogen NH4SCN as a structure regulator. This hierarchy structure remarkably enhances air stability resulting from the parallel growth of 2D PEA(2)SnI(4) as the surface layer. We then explore the hierarchy structure perovskite films in planar structural solar cells, which generate a PCE up to 9.41%. The device retains 90% of its initial performance for almost 600 hr. Our results suggest that adding removable NH4SCN in a perovskite precursor can significantly improve the stability and photovoltaic performance of Sn perovskite. This finding provides a powerful strategy to manipulate the structure of low-dimensional perovskite in order to enhance the performance of perovskite solar cells.

The stability of perovskite is a bottleneck for the application of perovskite solar cells. Herein, 4-ethylamine Phenylphosphate disodium salt (EAPP) was explored as a functional surface ligand to passivate perovskite surface. As the addition of 1 mol% of EAPP, the degradation of the film in high humidity condition was effectively reduced. Solar cells based on EAPP doped perovskite film show merely slight decrease of its initial efficiency in high humidity condition, whereas the control device show catastrophic decrease. Apart from as a passivating molecule to protect perovskite from contacting with water, EAPP show function as a reducing reagent to bond with hydrogen iodide formed in perovskite decomposition.

Halide perovskites have emerged as superstar materials for optoelectronic devices. Besides the fever of research in solar cells, these materials show great promise on light emitting diodes (LEDs), photodetectors and lasers as well. Rapid advances in bulk perovskite materials aroused universal interest for the development of perovskite nanocrystals, inspired by the great progress of classic colloidal semiconductor quantum dots. Perovskite nanocrystals have been synthesized based on solution process and exhibited high luminescence quantum yield, sharp emission peak, and emission color tunability. Significant progresses have been made about the application of perovskite nanocrystals for LED and lasers in recent years. In this paper, we will comprehensively introduce the synthesis strategies, physical and chemical characteristics, as well as their applications in optoelectronic devices.