Initiated Chemical Vapor Deposition of Poly(vinylpyrrolidone) Thin Films

Poly(vinylpyrroldione) (PVP) is a water soluble polymer produced from the N-vinylpyrrolidone monomer. It has applications in a variety of industrial fields. Here in this work, PVP is studied for new applications in dye sensitized solar cells (DSSCs) and surface patterning. Initiated chemical vapor deposition (iCVD) is used to deposit PVP under varying conditions such as reactor pressure and substrate temperature. The deposition kinetics was analyzed and found to be dependent on the rate of monomer adsorption from the vapor phase to the substrate surface. These results aided in identifying the ideal crosslinking and pore filling conditions for integrating PVP into DSSCs by iCVD. Fabricated polymer electrolyte DSSCs using PVP prove to have high open circuit voltage and fill factor that produced cells with higher efficiencies than equivalent liquid electrolyte DSSCs, 1.21 compared to 0.80 %. Further studies were performed on the deposition kinetics of PVP deposited under supersaturated conditions of the monomer. Typically, under supersaturation, the monomer condenses randomly on the surface and does not produce a smooth, thin film. However, PVP is found to deposit uniform films on substrates that have low monomer contact angles, which suggests that monomer wettability has a strong effect on resulting film morphology. For substrates with higher monomer contact angles, PVP growth rate is near-zero. Therefore, by utilizing the differences in growth under supersaturated conditions due to differences in surface wettabilities, selective deposition of PVP using iCVD was successfully demonstrated.