Enhanced stability of perovskite CsPbBr3 nanocrystals via dual passivation with Al(acac)3 and commercial polymer for solar cell encapsulation application

Abstract

To improve the stability of CsPbBr₃ perovskite nanocrystals (PNCs), a facile in situ synthesis route was developed, followed by surface passivation with aluminum acetylacetonate (Al (acac)₃) and encapsulation using a commercial polyolefin elastomer (POE). Through this simple polymer scraping process, the CsPbBr₃/Al (acac)₃/POE composite films were obtained, in which the PNCs with sizes of 10∼15 nm were uniformly dispersed in the polymer and protected by both inorganic ligands and polymer. The as-obtained nanocomposite films also exhibit good flexibility, tensile and fluorescence properties. Owing to the effective passivation of surface defects, the PL intensity of CsPbBr₃ NCs was increased by 29% after incorporating the Al (acac)₃ ligand. Meanwhile, it was found that the Al (acac)₃ ligand also facilitates enhancing the thermal/water stability of CsPbBr₃/POE film: the film after passivation retained 63% of the initial intensity after 15 days of soaking in water, as well as remained 45% of the initial intensity after 5 h of heating at 85 °C. Both the stability values were significantly higher than those of the reference sample CsPbBr₃/POE. In terms of device applications, CsPbBr₃@ Al (acac)₃/POE could be applied as a photovoltaic adhesive film for enhancing the power conversion efficiency of the crystal Si solar cell. By using a CsPbBr₃@ Al (acac)₃/POE film, the absolute power conversion efficiency (PCE) of a standard solar cell was improved by 0.55% (from 12.01% to 12.56%), which was higher than those of photovoltaic cells covered with pure POE film (0.29%) and CsPbBr₃/POE film (0.43%), respectively. The performance enhancement can be attributed to the down-conversion effect of PNCs, which convert ultraviolet light into visible emission centered at 520 nm, thereby improving the utilization of the solar spectrum.