Enhancing the Stability of Formamidinium Lead Iodide Solar Cells Using FAI·PbI₂ Powder and Silicon Quantum Dots

Intensive research on formamidinium lead iodide (FAPbI<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>) has led to record-breaking conversion efficiencies, but stability remains a significant challenge. To address this, we focused on synthesizing formamidinium iodide lead iodide powder (P-FAI·PbI2) and incorporating Si quantum dots (QDs) into P-FAPbI<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>-based films. P-FAI·PbI2 demonstrated improved film stability under light exposure in humid conditions, retaining its color for 108 days, compared to 20 days for FAPbI<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> derived from traditional PbI<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> precursors. Solar cells fabricated under these conditions exhibited superior stability: FAPbI<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> devices based on the traditional PbI<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> precursor degraded completely after 24 hours, whereas P-FAI·PbI2-based devices maintained their performance. The addition of Si QDs blended with P-FAI·PbI2 further enhanced stability, reducing color change and degradation in a constant temperature-humid chamber. XRD analysis revealed that homogeneously dispersed Si QDs within the absorption layer help stabilize the α-phase, preventing its transition to the unstable δ-phase.