Improved performance of polymer solar cells based on P3HT and ICBA using alcohol soluble titanium chelate as electron collection layer

We demonstrate efficient polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and fullerene derivatives ether Indene-C60 Bisadduct (IC60BA) or Indene-C70 Bisadduct (IC70BA)) by using solution-processed titanium(IV) oxide bis(2,4-pentanedionate) (TOPD) as electron collection layer (ECL) between the Al cathode and photoactive layer. The TOPD buffer layer was simply prepared by spin-coating isopropanol solution of TOPD on active layer and then baked at 80 °C for 15 min. The short-circuit current density (Jsc) and the open-circuit voltage (Voc) of the devices can be simultaneously and significantly improved by optimizing the electron collection layer, the photoactive layer and the device fabrication conditions. The power conversion efficiency (PCE) of the P3HT:IC60BA BHJ device with TOPD buffer layer reaches 5.0% under the illumination of AM1.5G, 100 mW/cm2, which is increased by 27% in comparison with that (3.9%) of the device without TOPD buffer layer under the same experimental conditions. When IC70BA was chosen instead of IC60BA, the BHJ device could show better performance with PCE of 5.59%. The results indicate that TOPD is a promising electron collection layer for PSCs.

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► Titanium(IV) chelate (TOPD) is adopted as the electron collection and hole blocking layer for polymer solar cells.
► Alcohol solubility of TOPD facilitates to form multilayer devices by solution process.
► The insertion of TOPD layer can increase the electron mobility and decrease the resistance of whole device.
► Postproduction heat treatment can further improve the performance of the PSCs.