Tuning the gallium content of metal precursors for Cu(In,Ga)Se2 thin film solar cells by electrodeposition from a deep eutectic solvent

Abstract

Controlling the Ga incorporation of Cu-In-Ga metal precursors for Cu(In,Ga)Se2 (CIGS) solar cells is one of the main challenges for low cost electrodeposition processes, mainly due to the difficulty in electrodepositing metallic Ga from aqueous electrolytes. In this work we use the deep eutectic solvent (DES) Choline Chloride : Urea (ChCl : U - 1 : 2) to efficiently codeposit In-Ga on Cu and Mo electrodes. We control the Ga/(Ga+In) (Ga/III) ratio of the films via the mass fluxes. The electrochemical behavior of ChCl : U containing GaCl3 and InCl3 is studied by rotating disk electrode cyclic voltammetry (CV) on Mo and Cu electrodes. CV revealed on both Mo and Cu electrodes that the electrochemical behavior of the ChCl : U-GaCl3-InCl3 system is the superposition of the individual In and Ga electrochemistry. On a Cu electrode the morphology, crystal structure and element distribution of the deposits were a function of the Ga/III ratio. We demonstrate the precise control of Ga incorporation over a large composition range from 0.1 ≤ Ga/III ≤ 0.9 and proved that ED from DES is a straightforward, robust and efficient process. First solar cells based on Mo/Cu/In-Ga metal stacks achieved efficiencies as high as 7.9% with a Voc of 520 mV.

Evaluation of toxicity and biodegradability for cholinium-based deep eutectic solvents

“…32 The toxicity assessment DESs on Cyprinus carpio in particular is very useful for future involvement of DESs in the industry. 35,36 Lately, choline based DESs were considered to be enzyme activators and stabilizers. 34 The fungi strain Aspergillus niger (A. niger) was selected based on their common usage in fermentation processes, enzyme production, and biochemical applications.…”

Insights into the Properties of Deep Eutectic Solvent Based on Reline for Ga-Controllable CIGS Solar Cell in One-Step Electrodeposition

“…21 Malaquias et al used Reline to deposit In-Ga on Cu and Mo electrodes and finally obtained solar cell with a 7.9% efficiency. 15 Chen at al reported a 3.87% CZTS solar cell efficiency by co-electrodepositing Cu-Zn-Sn precursor thin films in Reline. 24 Although these studies show the viability of Reline as a green electrolyte, its micro-structure and electrochemical properties are rarely reported and the formed metal complexes in Reline are also needed further investigation.…”

“…[10][11][12][13] However, most of the works are carried out in aqueous solvents, in which hydrogen evolution reaction (HER) leads to low plating efficiencies and pinholes in the plating layer. 14,15 To avoid the occurrence of HER, researchers in recent years have turned to deep eutectic solvents (DES) as an electrolyte for electrochemical reactions due to their wide electrochemical window, high ionic conductivity, high solvation capacity, negligible vapor pressure and excellent stability. [16][17][18][19][20] Besides, DES, as a subclass of ionic liquids (ILs), is a green electrolyte for application in electroplating.…”

“…[16][17][18][19][20] Besides, DES, as a subclass of ionic liquids (ILs), is a green electrolyte for application in electroplating. [14][15][16][21][22][23] Reline, as one application of DES, is formed by choline chloride and urea at the ratio of 1:2. Harati et al fabricated successfully stoichiometric CIGS thin film by the one-pot electrodeposition in Reline as electrolyte.…”

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

“…However, for Mo/Cu substrates, an improvement in the Cu-Ga films film adhesion (Fig. 6b) [79]. The same group reported an efficiency of 9.8% for CIGSSe thin films.…”