Improving the TiO₂ electron transport layer in perovskite solar cells using acetylacetonate-based additives

We developed a facile and quantitative method to improve the electron transport properties and resulting device performances of perovskite solar cells based on post-incorporation of various acetylacetonate additives. Previous studies rely on synthesis or soaking processes with limited additive control. Here, our acetylacetonated-based additives are used as effective intermediate gels to interact with TiO₂ nanocrystals using a simple approach. The incorporation process can be controlled effectively and quantitatively using a range of additives from divalent (II), trivalent (III), and tetravalent (IV) to hexavalent (VI) acetylacetonate. Electronic parameters of solar cell devices, such as short circuit current (J_sc) and fill factor (FF), are enhanced, regardless of the different valencies of the additives. Zirconium(iv) acetylacetonate was found to be the most effective additive, with average PCE improved from 15.0% to 15.8%. Detailed characterization experiments including transient photoluminescence spectra, ultra-violet photoelectron spectroscopy, photovoltage decay, and photocurrent decay indicate an improved interface with improved carrier extraction originating from the TiO₂ modification.