Alcohol soluble titanium(IV) oxide bis(2,4-pentanedionate) as electron collection layer for efficient inverted polymer solar cells

We demonstrate efficient inverted polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) by using solution-processed titanium(IV) oxide bis(2,4-pentanedionate) (TOPD) as electron collection layer (ECL) between the indium tin oxide (ITO) electrode and photoactive layer. The TOPD buffer layer was prepared by spin-coating isopropanol solution of TOPD on ITO and then baked at 140 °C for 5 min. The power conversion efficiency (PCE) of the inverted PSC with TOPD buffer layer reaches 4% under the illumination of AM1.5G, 100 mW/cm2, which is increased by 76% in comparison with that (2.27%) of the inverted device without TOPD ECL. The results indicate that TOPD is a promising electron collection layer for inverted PSCs.

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► Alcohol soluble titanium(IV) chelate (TOPD) was used as electron collection layer for inverted polymer solar cells.
► TOPD layer was annealed at low temperature (<150 °C).
► Device with TOPD buffer layer exhibited greatly improved performance in comparison with the device without TOPD.
► TOPD buffer layer shows good ability of electron collection after thermal annealing.