Se-containing inks for the formation of CuInSe2 films without gas-phase selenization

• Se-containing salts stabilize sols of CuInS2 nanocrystals and Se particles.
• Annealing leads to formation of CuInSe2 films avoiding gas-phase selenization.
• Use of (N2H5)2Se avoids formation of secondary phases during selenization.
• Incorporation of Se particles enhances selenization and recrystallization.

Today, almost all solution-processed absorber layers for CIGS thin-film solar cells require a gas-phase selenization step after film deposition. In this contribution, the addition of excess selenium to CIGS precursor inks, either as elemental Se particles or Se2−-containing salts, is investigated as an alternative way to induce selenization during thermal annealing. Most importantly, we find that (N2H5)2Se is a selenium-containing additive that both stabilizes CuInS2 nanocrystal inks and induces the formation of a pure CuInSe2 phase.

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