1. Fabrication of Hybrid Solar Cells using ZnS Nanoparticles
N. Chaudharya, R. K. Bhardwaja, N. Guptaa, G. D. Sharmaa, V. Guptaa, K. Banerjeeb and S. Chanda
aOrganic and Hybrid Solar Cell Group, National Physical Laboratory (CSIR), New Delhi, India.
bDiscipline of Chemistry, School of Science, IGNOU, New Delhi, India.
Brief Overview
Introduction
ZnS is an important inorganic material for a variety of applications including photoconductors, solar cells, field effect transistors, sensors, transducers optical coatings and light-emitting materials. Inorganic nano-particles have found potential application in various electronic devices. Synthesis, shape and size control are important issues for nano-particles research. ZnS has wide band gap ranging from 3.5 to 3.8 eV, which can be tuned by controlling the size of the nano-particles.
Synthesis and characterization of ZnS nanoparticles
We have synthesized ZnS nano-particles using aqueous chemical method. In this method, we take zinc chloride, dissolved in distilled water and keep it on stirrer using with C10 magnetic bead at 500 rpm. When solution is clear, then drop by drop addition of sodium sulfide solution is done, so when reaction is complete white color of ZnS nanoparticles is prepared and separated out using ultracentrifuge and several times washing with distilled water at 5 degree centigrade temperature and 7000 rpm and dried in vacuum oven at 50 degree centigrade temperature and characterized by UV-Vis spectroscopy (Fig.1). The absorption edge of ZnS nanoparticles at 317 nm (3.8 eV), which is slightly blue shifted from that of bulk ZnS (340 nm, Eg = 3.65 eV).,AFM (Fig 4 a,b)) It shows a very high roughness of the layer. It can be assumed that the nanoparticles aggregated to very big clusters and that the layer is highly phase separate. From AFM image, morphology of the nanoparticles can be observed, which in this case is spherical. TEM (Fig 2): The particles are seen to be nearly spherical and the sample morphology mainly consisted of tightly agglomerated particles. XRD (Fig.3): The XRD study indicates the presence of zinc sulfide (ZnS) nano particles, but some peaks slightly shifted due to the multilayer. Wide peaks in the X-ray diffraction pattern suggests presence of nanometric particles,and (Fig.5) show FTIR spectra
Fig . 1 UV-vis absorption spectra of ZnS
Fig. 3 X-ray diffraction pattern of ZnS nanoparticles
Fig. 2 TEM image of ZnS nanocrystals
Fig. 4 (a, b) AFM picture of a spin coated ZnS nanoparticles on glass
Fig . 5 FTIR spectrum of ZnS nanoparticles
Device fabrication and characterization
ZnS nanoparticles were blended with poly(3-hexyl thiophene) (P3HT) and organic photovoltaic devices were fabricated on the cleaned and pre-patterned ITO coated glass substrates in different ratios of P3HT and ZnS in the configuration(Fig.8) ITO/PEDOT:PSS/P3HT:ZnS/Al using with spin coater(Fig.6) for active materials casting and deposition for aluminum as cathode electrode using vacuum coating unit(Fig.7) Current-voltage (I-V) characteristics of these devices show promising results as Voc =4.23E-01, Jsc=4.88E-05, Efficiency=0.0047, Fill Factor=
Fig. 6 Spin Coater
Fig. 8 Architecture of an organic photovoltaic device
Fig. 7 Glove Box
Conclusion
We have successfully done synthesis of ZnS nano particles and characterized data prove that size ,shape, and band gap are small and device result are promising with ZnS : P3HT composite and further work is counting for better result.