Dye Sensitized Solar Cells Incorporating Polyelectrolyte Multilayer Composites
- PDF / 1,911,411 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 13 Downloads / 207 Views
L1.5.1
Dye Sensitized Solar Cells Incorporating Polyelectrolyte Multilayer Composites Geoffrey M. Lowman, Hiroaki Tokuhisa, Jodie L. Lutkenhaus, Paula T. Hammond Department of Chemical Engineering, Massachusetts Institute of Technology Cambridge, MA 02139, U.S.A. ABSTRACT Dye sensitized solar cells (DSSC’s) are constructed using TiO2 electrodes synthesized by aqueous liquid phase deposition in combination with microcontact printing techniques or porous thin film template methods. Layer-by-layer deposition of polyelectrolytes is used to produce an ionic conducting solid-state electrolyte thin film, which is enhanced by post-processing in oligoethylene glycol diacid (OEGDA). The impact of TiO2 film architecture, as well as the thin film electrolyte, on device performance is discussed. INTRODUCTION The emerging need for inexpensive renewable energy sources has stimulated new techniques and materials for the production of efficient photovoltaic devices. One of the most heavily studied of this new class of inexpensive photovoltaic device is the dyesensitized solar cell (DSSC).1 Over the last decade, DSSC’s based on mesoporous TiO2 have shown the potential to replace silicon as an inexpensive semiconductor material for solar energy conversion. Typically, high performance is achieved (over 10% efficiency) when an I3-/I- is employed as the redox couple in a liquid electrolyte. The ability to create thin polymer films that can effectively replace liquid electrolytes is one of the most important steps toward the improvement of photovoltaic performance, due to the longterm durability of solid-state electrolytes compared to liquid-based devices. Several methods have been developed for the production of solid-state or quasi-solid-state DSSC’s, including traditional solid-state polymer electrolytes2, gels formed from ionic liquids3, or hole conducting polymers4 and small molecules.5 Layer-by-layer (LbL) deposition of oppositely charged polyelectrolytes6 has proven a viable solid-state alternative to liquid electrolytes for photovoltaic applications in a DSSC architecture. Our laboratory has recently demonstrated relatively high roomtemperature ionic conductivity in LbL polyelectrolyte thin films.7 By using weak polyelectrolytes (where charge density can be modified by adjusting deposition pH conditions), such as linear poly(ethyleneimine) (LPEI) and poly(acrylic acid) (PAA), we have been able to create thin films containing greater numbers of mobile ions. In the fully hydrated state these composites show ionic conductivities on the order of 10-5 S/cm2.7 In order to achieve comparable conductivities at atmospheric humidity, oligoethylene glycol dicarboxylic acid (OEGDA) is introduced via direct adsorption into the fully formed multilayer. The second critical component of the DSSC photovoltaic investigated in this work is the TiO2 electrode. Traditionally, this layer is made by repetitive screen-printing of a paste of nanoparticles, which are sintered into a mesoporous matrix. In addition, light scattering particles can be added t
Data Loading...
