title: Influence of 4-guanidinobutyric acid as coadsorbent in reducing recombination in dye-sensitized solar cells.
abstract: Dye-sensitized solar cells based on nanocrystalline TiO(2) have been fabricated with an amphiphilic ruthenium sensitizer [Ru (4,4'-dicarboxylic acid-2,2'-bipyridine) (4,4'-bis(p-hexyloxystyryl)-2,2'-bipyridine)(NCS)(2)], coded as K-19, and 4-guanidinobutyric acid (GBA) as coadsorbent. The cells showed a approximately 50 mV increase in open-circuit voltage and a similar current in comparison with cells without GBA cografting. The performance of both types of devices was evaluated on the basis of their photocurrent-voltage characteristics, dark current measurements, cyclic voltammetry, electrochemical impedance spectroscopy, and phototransient decay methods. The results indicate that GBA shifted the conduction band of TiO(2) toward a more negative potential and reduced the interfacial charge-transfer reaction from conduction band electrons to triiodide in the electrolyte (also known as the back reaction). In addition, the devices with GBA cografting showed an excellent stability with a power conversion efficiency of approximately 8% under simulated full sunlight (air mass 1.5, 100 mW cm(-2)) during visible light soaking at 60 degrees C.
authors.affiliation: Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland.
authors.forename: Zhipan
authors.initials: Z
authors.lastname: Zhang
authors.forename: Shaik M
authors.initials: SM
authors.lastname: Zakeeruddin
authors.forename: Brian C
authors.initials: BC
authors.lastname: O'Regan
authors.forename: Robin
authors.initials: R
authors.lastname: Humphry-Baker
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel