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.