EKSTRAK ZAT WARNA ALAM DARI BIJI KESUMBA SEBAGAI FOTOSENSITISER PADA FOTOANODA SERAT NANO TiO2 UNTUK SEL SURYA; NATURAL DYES EXTRACTED FROM ACHIOTE SEEDS AS PHOTOSENSITIZER ON TiO2 NANOFIBERS PHOTOANODE FOR SOLAR CELLS

Risya Sasri, N

2014 | Disertasi | PROGRAM STUDI S2 KIMIA

Extraction of natural dyes from achiote seeds (Bixa orellana L.) using acetone and study of their interaction with Fe(III) as photosensitizers on TiO2 nanofiber photoanode in dye sensitized solar cells (DSSC) have been carried out. Dyes interaction with Fe(III) was performed using Fe(NO3)3 solution. Characterization of the dyes were performed using UVVis and infrared spectrophotometer. TiO2 nanofibers photoanode was fabricated by electrospinning using titanium(IV) tetraisopropoxide (TTIP) as titanium precursor Ti and polyvinyl pyrrollidone (PVP, Mw ~ 25000) as polymer matrix. The effect of polymer concentration and calcination temperature on the formation and crystalline phase of TiO2 nanofibers was studied. Characterization of nanofibers was performed using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and gas sorption analyzer (GSA). Natural dye sensitization on TiO2 nanofibers film deposited on conducting glass was assessed qualitatively using specular-reflectance UV-Vis spectrophotometer and quantitatively by determining current-voltage (I-V) curves and IPCE (incident photon to current conversion efficiency) spectra using PMII (1-propyl-3- methylimidazolium iodide) electrolyte and platinum-coated conducting glass as counter electrode. The results showed that the main component of achiote seed extract is bixin pigment with extinction coefficient of 53.7 Lg-1cm-1 in acetone. Interaction of Fe(III)-bixin extract resulted in bathochromic shift of the UV-Vis spectra indicating the bond formation between bixin and Fe(III). TiO2 nanofibers were obtained at optimum concentration of PVP as high as 50% (w/v) with calcination temperature of 450 oC. Low polymer concentration led to the formation of beads on nanofibers, whereas high temperature calcination induced the fiber morphology to collapse. The resulted TiO2 nanofibers were anatase crystalline phases with surface area (SBET) of 73.17 m2/g, diameter of ~150-200 nm and band gap energy of 3.27 eV. It is also shown that TiO2 nanofibers photoanodesprovides higher solar cell efficiency than those of commercial TiO2 while TiO2 nanofibers/bixin generates higher efficiency than the Fe(III)-bixin extract sensitized photoanodes.

Kata Kunci : achiote, TiO2 nanofibers, electrospinning, solar cells