Quantum Dots Coupled to an Oriented Two-Dimensional Crystalline Matrix for Solar Cell Application.

Colloidal quantum dots (QDs) have emerged as promising materials to harness panchromatic solar light, owing to their size-tunable optoelectronic properties. Advancements in surface passivation strategy and processing technique have contributed immensely to their developments in photovoltaic applications. Recently, surface passivation using halometallate ligands was shown to form a protective shell layer, which reduced the structural and energetic disorder in the QD solid. Here, we report lead sulfide (PbS) QDs coupled to an oriented two-dimensionally (2D) confined crystalline matrix by using a halometallate ligand. The QDs undergo surface reconstruction during the ligand treatment process, which leads to change in their shape, size, and axis length. We show that the 2D matrix is a combination of two distinct crystalline layers consisting of a crystalline Pb-amine complex and a 2D perovskite layer. The thickness of the matrix layer is modulated further by adjusting counter cations, which results in the enhancement in charge carrier mobility, carrier recombination lifetime, and diffusion length in the QD solid. 2D passivated QDs are implemented to fabricate photovoltaic devices with high power conversion efficiency of 9.1%.