Solution-processed quantum dot SnO2 as an interfacial electron transporter for stable fully-air-fabricated metal-free perovskite solar cells

Perovskite solar cells could strongly compete with the silicon solar cells in the market soon as illustrated in recent studies. In this work, promising and stable metal-free perovskite solar cells (PSCs) has been successfully fabricated using an inorganic SnO2/Quantum dot SnO2 (QD-SnO2) double layer as an efficient electron transport layer via a low-temperature solution process. The fully-air fabricated PSCs in the form of FTO/SnO2/QD-SnO2/CH3NH3PbI3/Carbon were tested at different annealed QD-SnO2 between 300 and 500 °C. The as-prepared QD-SnO2 and the fabricated devices are characterized by various techniques, including XRD, XPS, HR-TEM, FE-SEM, UV–vis–NIR spectroscopy, PL, and solar simulator. The prepared QD-SnO2 at 300 °C has shown well-ordered nanoparticles of 5.6 nm in diameter with superior carrier density (1.5 × 1015 cm−3) and highest carrier mobility (64.1 cm2·V-1·s−1), accelerating the carriers separation process within the cell. The best devices demonstrated a maximum power conversion efficiency (PCE) of 11.7%, VOC 0.81 V, JSC 19.5 mA·cm−2, and FF 74%. The presence of an interfacial layer of QD-SnO2 over the blocking SnO2 upsurges the band gaps alignment and accelerates the carriers extraction rate affecting the performance of the fabricated perovskite devices. Moreover, the optimized fabricated devices revealed a shelf stability-life of four months in humid air (40%–50%) with >83% of its initial PCE. This simple synthetic approach can develop the opportunities to transfer the cell from the lab to the market, which will be compatible with large-scale production.