Cu2ZnSnS4 Quantum Dots as Hole Transport Material for Enhanced Charge Extraction and Stability in All‐Inorganic CsPbBr3 Perovskite Solar Cells

All‐inorganic CsPbBr 3 perovskite solar cells (PSCs) have recently generated tremendous interest in next‐generation cost‐effective and stable photovoltaic devices. However, the commonly used costly and unstable organic hole transporting material (HTM) has so far prevented the further development and large‐scale application of PSCs. In this work, Cu 2 ZnSnS 4 quantum dots (CZTS QDs) are exploited as a novel inorganic HTM for CsPbBr 3 PSCs. Due to the well‐matched energy levels with the inorganic perovskite layer, a decent power conversion efficiency of 4.84% is achieved, which is quite comparable to the efficiency of the traditional device based on spiro‐OMeTAD HTM (5.36%). Moreover, the photoluminescence (PL) and impedance spectroscopy further demonstrate the more effective hole extraction and transfer properties of the CZTS QDs interface layer, making it a promising material for fabricating efficient and stable PSCs toward practical applications.