ИСТИНА

In recent years, hybrid organic-inorganic materials based on complex perovskite- complex lead halides have attracted a particular attention of the photovoltaic community. Despite the high efficiencies of perovskite solar cells, one of the major obstacles for the further development of the technology is the instability of oxide electron transport layer /perovskite interface, which results in lower power conversion efficiencies (PCE) and stability characteristics. In particular, bare zinc oxide electron transport layer (ETL), widely used in photovoltaics1, can cause a severe degradation of perovskite upon annealing[4]. Therefore, additional layers of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or [6,6]- phenyl-C61-butyric acid (PCBA) were introduced to passivate defects on zinc oxide and their effects on perovskite solar cell photovoltaic parameters were studied. We found that fullerenes bind to the zinc oxide surface, forming nanometers-thin layers, which block the direct contact of perovskite with the oxide, while the most part of the fullerenes is washed by the perovskite precursor upon the subsequent coating. The passivation of zinc oxide with fullerenes dramatically improved the charge extraction properties of the ETL resulting in an increase of solar cells’ PCE from 9% to 13.0% for PCBM and 14.7% for PCBA. Compared to the conventionally used PCBM2, an application of PCBA layer resulted in higher PCE, which was attributed to a better adhesion of the PCBA to the oxide surface due to its acidic groups and better charge extraction properties. Moreover, the PCBA layer can be coated using 18 times lower concentration than the PCBM, that provides a more cost-effective approach to oxide interface passivation.