For the purpose of increasing the energy conversion efficiency of dye-sensitized solar cells (DSSCs), carbon nanotubes (CNTs) were added to electrolyte and PtCl(4)-treated electrode. We used two different powders containing single-wall CNT (SWCNT) and multi-wall CNT (MWCNT). We added CNTs to PtCl(4)-treated electrode (called as CNT-counter electrode) or electrolyte (called as CNT-electrolyte) and then fabricated four kinds of DSSCs with SWCNT-counter electrode, MWCNT-counter electrode, SWCNT-electrolyte, and MWCNT-electrolyte. The efficiency of CNT-counter electrode DSSC was improved to 4.03% (SWCNT) and 4.36% (MWCNT). respectively. In case of CNT-electrolyte DSSC, MWCNT-electrolyte DSSC showed higher efficiency (4.2%) than SWCNT-electrolyte DSSC (3.62%). Compared with a standard DSSC without CNTs whose efficiency was 3.22%, the energy conversion efficiency increased up to about 26% and 24% for the MWCNT-electrode DSSC and the MWCNT-electrolyte DSSC, respectively. (C) 2009 Elsevier B.V. All rights reserved.