From crab shell to solar cell: a gel polymer electrolyte based on N-phthaloylchitosan and its application in dye-sensitized solar cells

Abstract

Chitosan, a biopolymer derived from crab shells which is insoluble in common organic solvents has been converted to the organosoluble N-phthaloylchitosan (PhCh) by reaction with phthalic anhydride in dimethylformamide (DMF). The formation and structure of PhCh was confirmed by the characteristic peaks of phthalimido and aromatic groups observed at 719, 1708 and 1772 cm⁻¹ and two sets of peaks centered at 3.0 and 7.5 ppm obtained from FTIR and ¹H NMR analyses respectively. Gel polymer electrolytes consisting of PhCh, ethylene carbonate (EC), and DMF with various amounts of tetrapropylammonium iodide (TPAI) and iodine were prepared. The interaction behavior between polymer–plasticizer–salt was thoroughly investigated using FTIR spectroscopy. The gel polymer electrolyte consisting of PhCh : EC : DMF : TPAI : I₂ in a weight ratio (g) of 0.1 : 0.3 : 0.3 : 0.12 : 0.012 showed the highest conductivity of 5.46 × 10⁻³ S cm⁻¹ at room temperature and exhibited the best performance in DSSCs with efficiency of 5.0%, with J_SC of 12.72 mA cm⁻², V_OC of 0.60 V and fill factor of 0.66.