Amidation-Retarded Synthesis of Perovskite Quantum Dots with Low Defect Density and Enhanced Carrier Transport for Efficient Light Emitting Diodes and Solar Cells.

Abstract

Perovskite quantum dots (PQDs) are promising for both solar cells (SCs) and light emitting diodes (LEDs) for their excellent optoelectronic characteristics and solution-processable fabrication. One of the general limitations for these two kinds of devices is that high defect density and poor charge transport, resulting from the unavoidable amidation-induced PbX₂ precipitation at high reaction temperature. In this work, an amidation-retarded synthesis strategy is proposed to prevent the PbX₂ precipitation and subsequent defect formation. Covalent metal halides are introduced to interrupt amidation by reacting with deprotonated oleic acid/protonated oleylamine. Then, free acids/amines are released to coordinate with PbX₂ and form regular lead-halide octahedra during nucleation-growth process. The synthesized CsPbI₃ PQDs exhibit lower defect density (5.1 × 10¹⁷ cm^-3), higher PLQY (92%) and better charge output capacity (≈8 times improvement). As a result, the LEDs and SCs achieve a maximum external quantum efficiency of 28.71% and power conversion efficiency of 16.20%, respectively, representing the state-of-the-art performance. Furthermore, the universality of such strategy has been demonstrated in red/green/blue LEDs, and could be expected in other optoelectronic devices.