Charge Transport Properties of PEG Substituted Phthalocyanine Polymers

Phthalocyanine polymers substituted with polyethylene glycol (PEG), PPEGPc, were synthesized and characterized by photoelectrochemistry. Thin film of phthalocyanine polymer was coated on a conductive ITO glass using a mixture of soluble PPEGPc in DMF. The PPEGPc film coated ITO electrode showed photocurrent of 3-16 mA/cm³ in a liquid electrolyte system containing hydroquinone. Phthalocyanine polymers substituted with polyethylene glycol showed higher photocurrent generation compared to that with unsubstituted polymer, suggesting that PEG units facilitate transport of generated charge carrier. Solid state PPEGPc photoelectrochemical cell, fabricated by using PPEGPc as charge generation materials and benzidine as a charge transport material, showed photo current of 0.04 ∼ 0.27 mA/cm³ under applied potential of 10V. Photocurrent generation was highly dependent on the PEG chain length, indicating that ethylene oxy groups in PEG participate charge transport. The photocurrent in solid state (i_p,s) was correlated to that in liquid cell (i_p,l) with a linear relationship of i _p,s = 0.025 + 0.015×i_p,l. Optimization of photocurrent generation in PPEGPc was attempted by varying the bridging group, PEG chain length, and end group of the polymer.