Mechanism of Electrochemical Deposition of Cu-In-Ga Mixed Oxide/Hydroxide Thin Films for Cu(In,Ga)Se₂Solar Cells

Abstract

Thin films of copper-indium-gallium mixed oxides/hydroxides are electrochemically deposited on molybdenum substrates in aqueous nitrate-based electrolyte in acidic conditions. The process is based on the local pH increase at the cathode surface due to the reduction of nitrate ions. A thermodynamical study shows that the electrochemically induced deposition of copper-indium-gallium mixed oxide/hydroxide films occurs at much higher potentials than their metallic counterparts. A voltammetric study presents the key role of Cu(II) reduction during the process to induce nitrate ions reduction, and shows that the deposition is then controlled by mass transfer of the Cu(II), In(III), Ga(III) species. The composition of the layer is remarkably precisely tuned in a large range of potential, which makes this process highly suitable for the synthesis of Cu(In,Ga)Se2 solar cells.

Semi-transparent photovoltaic glazing based on electrodeposited CIGS solar cells on patterned molybdenum/glass substrates

“…A key method allowing such selective deposition of CIGS is electrodeposition. Electrodeposited CIGS solar cells have been prepared in the classical configuration on glass/Mo substrate using an electrodeposition route introduced recently in the field, and known as the oxide route [12]. It consists in depositing a layer of mixed copper, indium and gallium oxides/ hydroxides by cathodic deposition from an aqueous solution of nitrate salts.…”

A short review on the advancements in electroplating of CuInGaSe2 thin films

“…An interesting alternative route for the inclusion of In (III) and Ga (III) is in the form of oxides/hydroxides using respective nitrate salts as reported by Duchatelet et al [63].…”

“…Using DES such as reline, successful electrodeposition of CGSe has been reported [75]. Electrodeposition of Cu-Ga alloy using copper-gallium nitrate salts is also a good approach, where the inclusion of Ga takes place in the form of oxides/ hydroxides [63].…”

Mechanistic Study of One-Step Cathodic Electrodeposition of Mixed Cu-In-Ga Oxide/Hydroxide Films with Hydrogen Peroxide Oxygen Precursor

“…17,18 This approach allows to deposit simultaneously the oxide/hydroxide of the three elements Cu, In and Ga at potentials much less negative than those expected for metallic indium or gallium. 19 With this process, the introduction of gallium in the film is easy and controllable. This is due to the fact that the strength of Ga-O bonds is higher than Ga-Se ones, which leads to a higher underpotential for the deposition of the oxide/hydroxide.…”

“…26 The process has been successfully introduced for the deposition of Cu-In-Ga oxide layers. 17,18 The oxygen source was nitrate ions which, during their electro-reduction in acidic aqueous solutions, consumes protons [17][18][19][20][21][22] and thus increases the interfacial pH leading to the precipitation of the oxides/hydroxides. However nitrate reduction also leads to the formation of nitrite species and other byproducts which could be detrimental for the long term stability of the electrolytes and their regeneration.…”