Highly Efficient Solar Cells Using Monodisperse Perovskite Quantum Dots

Bandtail broadening, arising from increases in polydispersity of colloidal quantum dots (CQDs), results in deficits of open-circuit voltage (V_OC) and deterioration of carrier transport in photovoltaics. For perovskite QDs (PQDs), which have recently been used as a promising photovoltaic absorber, the bandtail widens due to their increased polydispersity and non-uniform agglomeration during the polar anti-solvent-based purification process, which limits the device performance. Here, we report for the first time that the photovoltaic performance of fully-inorganic CsPbI₃ PQD solar cells can be improved by using monodisperse PQDs, which can reduce the energetic disorder with bandtail sharpening. To effectively reduce the polydispersity in polar anti-solvent-purified PQDs, we employ the size-selection process based on gel permeation chromatography, which can be used to systematically remove large and small particles from QD materials. Monodisperse PQDs obtained by this technique show higher photoluminescence quantum yield, narrower full-width at half maximum and lower Urbach energy than conventional irregular-sized PQDs. Through these advantages, the photovoltaic cells based on monodisperse PQDs show improved V_OC and photocurrent density, resulting in enhanced device performance up to 15.3% power conversion efficiency (PCE), which is higher than that of control devices based on irregular-sized PQDs (14.0% PCE).