Enhanced photovoltaic performance of inverted polymer solar cells through atomic layer deposited $Al_{2}$$O_{3}$ passivation of ZnO-nanoparticle buffer layer

International audienceIn this work, an atomic layer deposited (ALD) $Al_{2}$$O_{3}$ ultrathin layer was introduced to passivate the ZnO-nanoparticle (NP) buffer layer of inverted polymer solar cells (PSCs) based on P3HT:PCBM. The surface morphology of the ZnO-NP/$Al_{2}$$O_{3}$ interface was systematically analyzed by using a variety of tools, in particular transmission electron microscopy (TEM), evidencing a conformal ALD-$Al_{2}$$O_{3}$ deposition. The thickness of the $Al_{2}$$O_{3}$ layers was optimized at the nanoscale to boost electron transport of the ZnO-NP layer, which can be attributed to the suppression of oxygen vacancy defects in ZnO-NPs confirmed by photoluminescence measurement. The optimal inverted PSCs passivated by ALD-$Al_{2}$$O_{3}$ exhibited an ~22% higher power conversion efficiency than the control devices with a pristine ZnO-NP buffer layer. The employment of the ALD-$Al_{2}$$O_{3}$ passivation layer with precisely controlled thickness provides a promising approach to develop high efficiency PSCs with novel polymer materials