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AgInSe2 is a promising direct bandgap thin-film material with a rare n-type conductivity. Similar to thin film photovoltaic materials such as Cu(In,Ga)Se2 (CIGSe), which have achieved efficiencies as high as ~23%, AgInSe2 also crystallizes in a chalcopyrite phase while also being more tolerant to antisite defects due to higher defect formation energies resulting from more significant variations in cation sizes. AgInSe2 has a suitable bandgap of 1.24 eV, which lies in the high-efficiency region of the detailed balance limit. In this work, we have utilized a Dimethyl Formamide-Thiourea-Chloride-based solution-processed route to deposit a thin film of AgInS2 which is converted into AgInSe2 after a heat-treatment step in a selenium environment. AgInSe2 optoelectronic properties depend on the Ag/In ratio and the selenium heat-treatment conditions. Significant improvements in photoluminescence yield and lifetime are observed for Ag-poor films in selenium-rich conditions. X-ray Photoelectron Spectroscopy (XPS) measurements confirm a higher amount of selenium on the surface of films with improved optoelectronic properties. Furthermore, a high minority carrier lifetime of 9.2 ns and a Photoluminescence Quantum Yield (PLQY) of 0.013% is obtained without any passivating layer, which improved to 0.03% after CdS passivation. Hall effect measurements confirm that AgInSe2 has n-type conductivity with a moderate carrier concentration (10-14 cm-3), more suitable for a p-i-n architecture. XPS has further confirmed the moderate n-type conductivity.
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Large-Scale Synthesis of Semiconducting Cu(In,Ga)Se2 Nanoparticles for Screen Printing Application
During the last few decades, the interest over chalcopyrite and related photovoltaics has been growing due the outstanding structural and electrical properties of the thin-film Cu(In,Ga)Se2 photoabsorber. More recently, thin film deposition through solution processing has gained increasing attention from the industry, due to the potential low-cost and high-throughput production. To this end, the elimination of the selenization procedure in the synthesis of Cu(In,Ga)Se2 nanoparticles with following dispersion into ink formulations for printing/coating deposition processes are of high relevance. However, most of the reported syntheses procedures give access to tetragonal chalcopyrite Cu(In,Ga)Se2 nanoparticles, whereas methods to obtain other structures are scarce. Herein, we report a large-scale synthesis of high-quality Cu(In,Ga)Se2 nanoparticles with wurtzite hexagonal structure, with sizes of 10–70 nm, wide absorption in visible to near-infrared regions, and [Cu]/[In + Ga] ≈ 0.8 and [Ga]/[Ga + In] ≈ 0.3 metal ratios. The inclusion of the synthesized NPs into a water-based ink formulation for screen printing deposition results in thin films with homogenous thickness of ≈4.5 µm, paving the way towards environmentally friendly roll-to-roll production of photovoltaic systems.
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- Award ID(s):
- 2003783
- PAR ID:
- 10230107
- Date Published:
- Journal Name:
- Nanomaterials
- Volume:
- 11
- Issue:
- 5
- ISSN:
- 2079-4991
- Page Range / eLocation ID:
- 1148
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/nano11051148
