Microwave-synthesized aluminum, gallium and indium-substituted stannite nanocrystal absorbers for solar cell applications

Abstract

A novel family of Cu2FeXS4-x (X = Sn, Al, Ga & In) semiconductors with tetragonal stannite crystal structurehave been designed by a simple microwave assisted method. The impact of microwave power on the morphological, structural,spectroscopic and electrochemical properties were investigated. X-ray Diffraction (XRD) clearly revealed that the complete substitution of Sn (0.69 Å) with Al (0.54 Å), Ga (0.62 Å) and In (0.80 Å) did not affect the tetragonal arrangement of the stannite crystal structure except for a slight peak shift. High resonance scanning and transmission electron microscopy (HRSEM and HRTEM) revealed nano bullets, hexagonal prism, triangular nanoplates and spherical morphology with nanocrystal sizes ranging from 8 to 13 nm for CFXS nanocrystals. The UV–visible spectroscopy shows strong light absorption in the whole visible range with band gaps of between 1.2 and 1.6 eV suggesting its potential application as an absorber in thin film solar cells. Doctor blading method was used to coat CFXS nanocrystal inks on CdS coated ZnO nanorod arrays to fabricate a superstrate solar cell devices with the architecture ITO/ZnONRs/CdS/CFXS/Ag. The solar cell devices fabricated with copper iron tin sulfide (CFTS), copper iron aluminium sulfide (CFAS), copper iron gallium sulfide (CFGS) and copper iron indium sulfide (CFIS) absorbers displayed a power conversion efficiency (PCE) of 0.21%, 0.15%, 0.58% and 0.41% respectively. The photovoltaic response exhibited by the novel materials is quite positive and this shows that they can in fact be utilized to design solar cells with strong photovoltaic properties.