Formamidinium lead iodide perovskite photovoltaics with MoS₂ quantum dots

We present the formation of a composite film made out of formamidinium lead iodide (FAPI) and molybdenum disulphide quantum dots (MoS₂ QDs) and propose a corresponding photovoltaic device architecture based on a 'type-I' alignment of the two materials' electronic energy levels. The introduction of the MoS₂ QDs has not compromised the overall crystallinity of the FAPI film and the composite absorber has shown improved stability. We report on the benefits of this composite film and energy band arrangement as the photogenerated carriers in MoS₂ QDs, both positive and negative, are injected into the FAPI host matrix, resulting in an increased current density of 24.19 mA cm^-2 compared to a current density of 19.83 mA cm^-2 for the control device with FAPI only. The corresponding photoconversion efficiency increases from 12.6 to 15.0%. We also show that inclusion of MoS₂ QDs in FAPI films resulted in a notable improvement in the fill factor and open-circuit voltage of the solar cells. Most importantly, MoS₂ QDs enhanced the film stability by reducing defect formation and acting as passivating agents that minimize recombination losses and improve charge carrier transport. Our results suggest that a composite film in a type-I device architecture can introduce benefits for both future developments in perovskite solar cells and effectively tackling the longstanding challenges of carrier transport in QDs solar cells.