Quantum Dot Concentration-Mediated Synergistic Optimization of Absorber Thickness and Interface Defects in Infrared Quantum Dot/Perovskite Nanorod Array Solar Cells

Abstract

The thickness of the light-absorbing layer and interface defects are the key factors affecting the photovoltaic performance of perovskite solar cells. In this article, aiming at the problem of carrier recombination caused by the thickness of the light-absorbing layer and interface defects in infrared quantum dot/perovskite composite nanorod arrays, a strategy of synergistically optimizing the thickness of the quantum dot absorption layer and interface passivation performance by adjusting the concentration of PbS-PbI₂ quantum dots is proposed. Experimental results indicate that quantum dot concentration significantly influences light-absorbing layer properties. At 40 mg/mL, the absorber layer thickness increases to 27.5 nm, interface defect density decreases, carrier transport efficiency improves, near-infrared light absorption enhances, and optimal photovoltaic performance is achieved (J_sc = 14.72 mA/cm², PCE = 6.65%). When concentration exceeds 40 mg/mL, quantum dot agglomeration causes absorber thickness to sharply decrease to 20.5 nm, interface defect density increases, and both light absorption efficiency and photovoltaic performance decline (J_sc = 11.58 mA/cm², PCE = 4.41%). Through XRD, SEM, and EIS characterization, it was found that at a concentration of 40 mg/mL, a moderate thickness of the light-absorbing layer improves the near-infrared light capture ability, effectively passivates the interface defects through the Pb²⁺-I^- coordination bond, and optimizes the perovskite crystal quality and carrier kinetics. This article reveals the regulation of quantum dot concentration on device performance through the synergistic mechanism of “absorber layer thickness and interface defect-light absorption-photovoltaic performance,” which provides guidance for efficient interface engineering of the perovskite/quantum dot composite system.