Morphology control for highly efficient organic–inorganic bulk heterojunction solar cell based on Ti-alkoxide

Publication date: 1 February 2016
Source:Thin Solid Films, Volume 600
Author(s): Takehito Kato, Naoki Hagiwara, Eiji Suzuki, Yuki Nasu, Satoru Izawa, Kouichi Tanaka, Ariyuki Kato
The number of publications concerned with typical bulk-heterojunction solar cells that use fullerene derivatives and inorganic materials as electron acceptors has grown very rapidly. In this work, we focus on Ti-alkoxides as electron acceptors in the photoactive layers of fullerene-free bulk-heterojunction solar cells. We show that it is possible to control the morphology by adjusting the molecular structure and size of the Ti-alkoxides. The short-circuit current density (J sc) increased to 191 μA/cm² from 25 μA/cm² with a maximum, when the phase-separation structure was continuously formed to within about 20 nm below the exciton diffusion length by using either titanium(IV) ethoxide or isopropoxide as an electron acceptor. Within a thickness of 30 nm, the photoactive layer is not influenced by the electron transfer ability; thus, we demonstrate that the charge-separation efficiency is equivalent to that of a fullerene system.