Cu(In,Al)Se2 Photovoltaic Thin Film Solar Cell from Electrodeposited Stacked Metallic Layers

An improved technique for synthesis of Cu(In,Al)Se2 is demonstrated, associated with sequential electrodeposition of a stacked layer in the order of Cu/Al/In followed by annealing in selenium vapor. Many advantages such as adjustable constitutes composition, good polycrystalline structure, pure chalcopyrite phase, uniform and compact surface morphology are obtained compared to the film fabricated by conventional electrodeposition process. The film thickness and the concentration of each metal deposited were controlled by the flexibility parameters of deposition time. The influence of Al content on the crystal structure, surface morphology, photoelectrochemical performance, optical and electronic properties of the films were investigated. The crystal size decrease and the energy bandgap of Cu(In,Al)Se2 thin film increase gradually with the increasing Al were revealed. Impedance potential test reveals the manufactured Cu(In,Al)Se2 thin films are all p-type semiconductor and the carrier concentration increases with the Cu/(Al + In) and Al/(In + Al) ratio. Photoelectrochemical investigation of Cu(In,Al)Se2 films verified that a higher photocurrent was obtained with a relative lower Al content due to a narrower bandgap leading to lower-energy photon absorption and a lower carrier density and a larger grain size both benefitting the transfer of photogenerated carriers and decrease the recombination of charge carriers. The obtained optimum Cu(In,Al)Se2 thin film based solar cell has been theoretical modeling and simulated. A high PCE of 17.08% was gained implying its potential application in photovoltaic devices.