Environmentally Friendly AgBiS₂ Nanocrystal Inks for Efficient Solar Cells Employing Green Solvent Processing

Abstract

Solution-phase ligand-exchange process happens between two immiscible solvent phases, for one phase being nonpolar to dissolve organic ligands capped nanocrystals and the other being polar, with high dielectric constants, to provide effective screening of electrostatic attraction between oppositely charged ions. [6] Currently, the most widely used solvents in solution-phase ligand-exchange procedures are formamide (FA), N,N-dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO). [3,[7][8][9] However, these polar solvents are highly toxic, raising major concerns on overall environmental impact. [10] Moreover, occupational safety must be taken into account for operators in manufacturing or scientists in the lab, who may come into direct contact with the ink or inhale solvent fumes during fabrication. Investigation of alternatives for ink preparation and device fabrications offers an invaluable opportunity toward safe and upscalable photovoltaic manufacturing techniques. [11][12][13] Silver bismuth sulfide nanocrystals (AgBiS 2 NCs), in view of their favorable bandgap, high absorption and absence of toxic RoHS elements, are promising solution-processable materials for photovoltaic applications. [14][15][16] Solution-phase ligand-exchange method has been recently introduced into AgBiS 2 NCs, yet their performance has been lower than their solid-state ligand-exchanged counterparts. [7,17] Here, we report a facile solution-phase ligand-exchange method for the production of AgBiS 2 inks employing 3-mercaptopropionic acid (MPA) and methanol (MeOH) as the ligand and solvent pair. The resultant MPA capped nanocrystals can be easily dissolved in water, rendering the final ink used for device fabrication, completely environmentally friendly. Furthermore, implementing AgBiS 2 nanocrystal inks into fully green-processed photovoltaic devices, an efficiency up to 7.3% was achieved, along with superior air stability. Results and DiscussionThe AgBiS 2 nanocrystals are first synthesized following a standard air-free Schlenk line technique with oleic acid as the surface ligands. [14,16] Prior to the ligand exchange, nanocrystals were dispersed in octane, and 3-mercaptopropionic acid (3-MPA) was dissolved in methanol as ligand solution, as shown in Figure 1. The nanocrystal/octane was then mixed with MPA/methanol vigorously and the two phases became Silver bismuth sulfide nanocrystals (AgBiS 2 NCs) are emerging absorber materials for low-cost solar cells, owing to their solution-processability, environmentally friendliness, earth abundance, and high absorption coefficients. When it comes to green manufacturing technologies, besides the semiconductor materials, solvents play an equally important role. Here, solution-phase ligand-exchanged (SPLE) AgBiS 2 nanocrystal inks employing 3-mercaptopropionic (MPA) in methanol as a ligand solution are introduced. The resultant MPA capped AgBiS 2 nanocrystals can be fully dissolved in water, forming completely environmentally friendly nanocrystal inks. These nanocrystal inks allow the fabricatio...

Eco-friendly and ultrathin solar cells featuring nanocrystals: advances and perspectives

“…Konstantatos et al introduced 3-MPA as the ligand for the surface passivation of AgBiS 2 nanocrystals via the SPLE process and achieved a high PCE of 7.3%. 56 Optimizing surface ligand e.g., introducing inorganic-organic mixed ligands, may further reduce the trapassisted recombination of the active layer to improve device performance. Additionally, introducing environmentally friendly candidates to substitute the toxic solvents e.g., DMSO and DMF in the SPLE process is another critical challenge.…”

“…Additionally, Konstantatos et al employed the organic ligand 3-MPA and halide ligand to perform the SPLE process, which can enable a high PCE of 7.3%. 56 Strikingly, the ligand exchange process employed the environmentally friendly solvents methanol (MeOH) and octane to significantly lower environmental toxicity, and AgBiS 2 nanocrystals dispersed well in aqueous solution with a small amount of butylamine (Fig. 5d and e).…”

Toward efficient hybrid solar cells comprising quantum dots and organic materials: progress, strategies, and perspectives

“…13g–i). 57 Despite this great advancement, the photovoltaic performance of AgBiS 2 QD solar cells still lagged far behind those of lead chalcogenide QD solar cells (over 15% (ref. 181)) and perovskite QD solar cells (over 17% (ref.…”

“…The star nontoxic AgBiS 2 QDs have seen a dramatic surge due to their promising opto-electronic properties, including broad absorption range, high absorption coefficient, favorable energy landscape, and great ambient stability. [54][55][56][57] With joint efforts, the photovoltaic performance of AgBiS 2 QDSCs has been improved to over 9.0% in 2022 (Fig. 1b).…”

CuBiSe2 Quantum Dots as Ecofriendly Photosensitizers for Solar Cells

“…Ternary chalcogenides of class ABX 2 (I–III–VI) (A = Ag, Cu; B = Bi, Sb; X = S, Se) are garnering attention due to their compositionally tunable bandgap (1.4–2.6 eV), − excellent absorption coefficient (10 5 cm –1 ) 2 , moderate hole mobility, and as being alternatives to toxic materials. ,, Ag based materials were the first among the ternary chalcogenides that were applied to solar cells, followed by their modifications , and have presently crossed a power conversion efficiency (PCE) of 9% within a short span of time. However, copper ternary chalcogenide nanocrystals have an edge over them due to the cost factor.…”