Diketopyrrolopyrrole latent pigment-based bilayer solar cells

Two Diketopyrrolopyrrole based latent pigmentdonor materials were fabricated into thin film bilayer pho-tovoltaic devices featuring PCBM as the acceptor. Ther-mal deprotection of the thin film, carried out at 200∘C,returns the dye-like small molecule to the correspondingpristine pigment quantitatively. The connected evolutionof electrical and morphological features of pure thin filmsand blends are examined. A significant decrease in extinc-tion coefficient was noted and correlated both to intrinsicchanges of the electronic structure upon cleavage and toan increase in internal scattering due to extensive crys-tallization. Power conversion efficiencies of 0.33% wereachieved for bilayer devices, nearly doubling previous re-sults with latent pigment DPP devices, under comparableexperimental conditions.