Anatase colloidal solutions suitable for inkjet printing: Enhancing lifetime of hybrid organic solar cells

We describe a one-pot chemical synthesis to produce TiO2−x(OH)2x colloidal solutions that are suitable to be deposited, at 150 °C only, as interfacial electron transporting layer, in inverted organic solar cells. The crystallized nanoparticles were synthesized from the hydrolysis of [Ti8O12(H2O)24]Cl8HCl·7H2O in organic solvent, using solvothermal method at 120 °C. The UV-illumination of TiO2 colloidal solutions, before the deposition process, was found to improve the initial performance of solar cells. Compared to the usual sol-gel TiOx layer, no kink shape of the I/V curve is observed, indicating the good quality of the interfacial contact with the P3HT:PCBM blend of polymer. Additionally it is worth noting the significant improvement of the solar cells stability, characterized by a loss of power conversion efficiency limited to 17% after 6500 h over continuous AM 1.5 illumination.