Effect of Central Metals in the Porphyrin Ring on Photocurrent Performance of Cellulose Langmuir‐Blodgett Films

Abstract

Role‐sharing functionalized cellulose derivatives having Mg, Zn, Cu, and Pd porphyrins are used for photocurrent generation system fabricated by the LB technique, mimicking the array of natural photosynthetic light‐harvesting systems. These polymers exhibited different absorption and redox properties in solution depending on the central metal ions. On visible light illumination, the LB film generated anodic photocurrent in the order of Pd > free base > Zn > Cu > Mg. By inserting Pd ion, using myristoyl group, and adjusting the DS, the photocurrent quantum yield was 6.9 times as great as that of conventional porphyrin cellulose. These findings may provide opportunities for the design of a new class of organic solar cells, based on cellulose molecular characteristics. magnified image

Synthesis of (zinc(II) phthalocyanine)-containing cellulose derivative using phthalocyanine-ring formation reaction

“…The LB monolayer film of compound 5 on mica, quartz and ITO substrates could be prepared by the vertical dipping method, although some aggregates were observed in AFM image of the monlayer. The LB monolayer film of compound 5 showed photocurrent performance at 680 nm, whereas the LB monolayer films of the porphyrin-containing celluloses generated photocurrent in the range of 400 nm to 600 nm (Sakakibara and Nakatsubo 2010). Compound 5 is expected to be a complementary material of the porphyrin-containing cellulose derivatives for solar cell materials.…”

“…The photocurrent measurements were performed according to the method reported by Sakakibara and Nakatsubo (2010).…”

“…One of the proposed applications is the photocurrent generation system using porphyrin-containing cellulose derivatives (Sakakibara et al 2007;Nakatsubo 2008, 2010). Sakakibara and Nakatsubo (2010) have reported the fabrication of Langmuir-Blodgett (LB) films using 6-O-porphyrin-2,3-di-O-stearoyl cellulose or 6-O-porphyrin-2,3-di-O-myristoyl cellulose with high photocurrent generation performance. The cellulose backbone played an important role in the inhibition the porphyrin self-aggregation as a scaffold of porphyrin in the LB films.…”

“…(1) It was found in preliminary experiments, which will be published elsewhere, that the acyl groups more than fourteen carbons long were essential to good solubility in common organic solvents and formability of LB films in 6-O-porphyrin-2,3-di-O-acyl cellulose derivatives with various acyl groups from acetyl group (C2) to stearoyl group (C18). (2) The photocurrent performance of 6-O-porphyrin-2,3-di-O-myristoyl cellulose (C14 chain) has been found to be higher than that of 6-O-porphyrin-2,3-di-O-stearoyl cellulose (C18 chain) (Sakakibara and Nakatsubo. 2010).…”

Preparation of 6-azafulleroid-6-deoxy-2,3-di-O-myristoylcellulose

“…One of the proposals of cellulose derivatives for the advanced materials is the photocurrent generation system using porphyrin-containing cellulose derivatives as electron donor materials. [3][4][5] Sakakibara and Nakatsubo reported the Langmuir-Blodgett film of porphyrin-fullerene (C 60 ) system using the porphyrin-containing cellulose derivative and C 60 with high photocurrent generation performance. 4 Then, C 60 -containing cellulose derivative is also attractive for the photocurrent generation system as an electron acceptor material, because it is expected to be useful for forming an electron transporting pathway in the system.…”