(251c) Synthesis and Characterization of Solution-Processed AgInSe2 Thin Films As a Candidate for Low-Cost, High Efficiency Printable Photovoltaics

Solution processing of inorganic thin films has emerged over recent years as a promising approach for the high-throughput, low-cost manufacturing of thin film photovoltaic (PV) devices. Among the candidate PV materials under investigation, the chalcogenides Cu₂ZnSn(S,Se)₄ and Cu(In,Ga)(S,Se)₂ are among the most heavily researched, with champion device efficiencies reaching 12.6%¹ and 17.3%², respectively, through the hydrazine solvent system. However, both materials suffer from intrinsic defects and relative compositional complexity that complicate the attainment of higher efficiencies; problems which will become exacerbated when trying to maintain high-quality materials during large-area (i.e. module-scale) manufacturing. While numerous approaches have been presented to address these problems, we propose circumventing them altogether with the fabrication of a simple, stable, intrinsically low-defect inorganic material.

AgInSe₂ (AISe) has been shown to have low intrinsic defects, high carrier mobility, and a band gap well suited for the solar spectrum.^3,4 Despite the clear potential of this material, the literature addressing AISe, especially as a candidate PV material, is relatively sparse.

As the hydrazine system is dangerously toxic and explosive, we have taken advantage of the amine-thiol solution-processing route for the fabrication of AgInSe₂ thin films. This approach has key advantages over other solvent systems in that it is an oxygen-free system which can dissolve a wide array of pure metals and metal chalcogenides. This eliminates the need for metal halide precursors common to other solution routes, avoiding halide incorporation which has been shown to influence the electronic properties of the fabricated materials⁵. We have addressed the unique challenges presented by silver-containing amine-thiol solutions for the fabrication of stable inks which were then coated using a scalable auto-doctor blading approach and selenized to form phase-pure, large-grain chalcopyrite AISe thin films. For the first time, we have shown a scalable, impurity-free molecular precursor approach for the synthesis of high-quality AISe thin films, opening up new approaches for the fabrication of high efficiency thin film PV devices.

References:

(1) Wang, W.; Winkler, M. T.; Gunawan, O.; Gokmen, T.; Todorov, T. K.; Zhu, Y.; Mitzi, D. B. Device Characteristics of CZTSSe Thin-Film Solar Cells with 12.6% Efficiency. Adv. Energy Mater. 2014, 4 (7), 1–5.

(2) Zhang, T.; Yang, Y.; Liu, D.; Tse, S. C.; Cao, W.; Feng, Z.; Chen, S.; Qian, L. High Efficiency Solution-Processed Thin-Film Cu(In,Ga)(Se,S) 2 Solar Cells. Energy Environ. Sci. 2016, 9 (12), 3674–3681.

(3) Yoshino, K.; Kinoshita, A.; Shirahata, Y.; Oshima, M.; Nomoto, K.; Yoshitake, T.; Ozaki, S.; Ikari, T. Structural and Electrical Characterization of AgInSe 2 Crystals Grown by Hot-Press Method. J. Phys. Conf. Ser. 2008, 100 (4), 042042.

(4) Tell, B.; Shay, J. L.; Kasper, H. M. Room‐Temperature Electrical Properties of Ten I‐III‐VI 2 Semiconductors. J. Appl. Phys. 1972, 43 (5), 2469–2470.

(5) Marin, R.; Skripka, A.; Huang, Y.-C.; Loh, T. A. J.; Mažeika, V.; Karabanovas, V.; Chua, daniel h. c.; Dong, C.-L.; Canton, P.; Vetrone, F. Influence of Halide Ions on the Structure and Properties of Copper Indium Sulphide Quantum Dots. Chem. Commun. 2020.