Dangling Bond Defects: The Critical Roadblock to Efficient Photoconversion in Hybrid Quantum Dot Solar Cells

Abstract

Inorganic–organic hybrid materials based on silicon quantum dots (SiQDs) have been utilized for photovoltaic applications but suffer from rapid charge recombination and low carrier mobility. We present an ab initio investigation of charge dynamics to pinpoint the source of this severe problem, and our results indicate that such devices show great promise provided that dangling bond (DB) defects can be sufficiently removed. Without DBs, the predicted charge transfer (CT) rate is much higher than that of photoluminescence (PL), while the electron hopping (EH) proceeds more quickly than interfacial charge recombination (CR). In contrast, one DB in a SiQD leads to a dramatic enhancement, by 10 orders of magnitude, in the CR rate and a reduction of the EH rate by 4 orders of magnitude, so that the diffusion of carriers to electrodes becomes extremely difficult. Although other factors, such as dot size distribution and oxidation, also play a deleterious role in device performance, their effects are deemed much ...