title: Post-assembly atomic layer deposition of ultrathin metal-oxide coatings enhances the performance of an organic dye-sensitized solar cell by suppressing dye aggregation.
abstract: Dye aggregation and concomitant reduction of dye excited-state lifetimes and electron-injection yields constitute a significant mechanism for diminution of light-to-electrical energy conversion efficiencies in many dye-sensitized solar cells (DSCs). For TiO2-based DSCs prepared with an archetypal donor-acceptor organic dye, (E)-2-cyano-3-(5'-(5''-(p-(diphenylamino)phenyl)-thiophen-2''-yl)thiophen-2'-yl)acrylic acid (OrgD), we find, in part via ultrafast spectroscopy measurements, that postdye-adsorption atomic layer deposition (ALD) of ultrathin layers of either TiO2 or Al2O3 effectively reverses residual aggregation. Notably, the ALD treatment is significantly more effective than the widely used aggregation-inhibiting coadsorbent, chenodeoxycholic acid. Primarily because of reversal of OrgD aggregation, and resulting improved injection yields, ALD post-treatment engenders a 30+% increase in overall energy conversion efficiency. A secondary contributor to increased currents and efficiencies is an ALD-induced attenuation of the rate of interception of injected electrons, resulting in slightly more efficient charge collection.
authors.affiliation: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Ho-Jin
authors.initials: HJ
authors.lastname: Son
authors.forename: Chul Hoon
authors.initials: CH
authors.lastname: Kim
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Kim
authors.forename: Nak Cheon
authors.initials: NC
authors.lastname: Jeong
authors.forename: Chaiya
authors.initials: C
authors.lastname: Prasittichai
authors.forename: Langli
authors.initials: L
authors.lastname: Luo
authors.forename: Jinsong
authors.initials: J
authors.lastname: Wu
authors.forename: Omar K
authors.initials: OK
authors.lastname: Farha
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Hupp
keywords: atomic layer deposition (ALD); dye aggregation; dye-sensitized solar cells (DSCs); interfacial electron injection; post-treatment