Layer-by-layer nanoassembly of copper indium gallium selenium nanoparticle films for solar cell applications

Abstract

Thin films of CIGS nanoparticles interdigited with polymers have been fabricated through a cost-effective nonvacuum film deposition process called layer-by-layer (LbL) nanoassembly. CIGS nanoparticles synthesized by heating copper chloride, indium chloride, gallium chloride, and selenium in oleylamine were dispersed in water, and desired surface charges were obtained through pH regulation and by coating the particles with polystyrene sulfonate (PSS). Raising the pH of the nanoparticle dispersion reduced the zeta-potential from +61 mV at pH 7 to -51 mV at pH 10.5. Coating the CIGS nanoparticles with PSS (CIGS-PSS) produced a stable dispersion in water with -56.9 mV zeta-potential. Thin films of oppositely charged CIGS nanoparticles (CIGS/CIGS), CIGS nanoparticles and PSS (CIGS/PSS), and PSS-coated CIGS nanoparticles and polyethylenimine (CIGS-PSS/PEI) were constructed through the LbL nanoassembly. Film thickness and resistivity of each bilayer of the films were measured, and photoelectric properties of the films were studied for solar cell applications. Solar cell devices fabricated with a 219 nm CIGS film, when illuminated by 50 W light-source, produced 0.7 V open circuit voltage and 0.3 mA/cm2 short circuit current density. © 2012 A. Hemati et al.