Beneficial effects of in situ photopolymerized poly[di-(ethylene glycol)-2-ethyl hexyl ether acrylate] (PDEA) in the pores of dye-coated TiO2 film on the photovoltaic characteristics of dye-sensitized solar cells (DSSCs) are reported. We have found remarkable enhancements of short-circuit photocurrent (J(sc)) by 39% and of open-circuit voltage (V-oc) by 40 mV for the PDEA-modified DSSC compared with those of a conventional DSSC. This led to an enhancement in the overall solar energy conversion efficiency of 4.9% for the modified cell over 4.0% for a cell without PDEA at 100 mW/cm(2). Moreover, the PDEA modification has led to improved long-term stability of the DSSC. Analyses of optical absorption and transient photocurrent of the cells suggest that the increased concentration of photo-injected electrons as a result of blocking of trap states in TiO2 contributes to the enhancement in the J(sc) of PDEA-modified DSSCs. The V-oc increase is attributed to an improved screening of the conduction band electrons from I-3(-) ions in the presence of PDEA adhered to TiO2 particles. (c) 2005 The Electrochemical Society. All rights reserved.