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We report on quantum confined Ge1-x-ySi_ySn_xnanocrystals demonstrating both size- and composition-tunable direct visible/NIR emission (1.77 – 2.47 eV) and recombination dynamics. Temperature-dependent time-resolved photoluminescence suggests significant enhancement of oscillator strengths with Si incorporation. 

Group IV alloy nanocrystals (NCs) are a class of direct energy gap semiconductors that show high elemental abundance, low to non-toxicity, and composition-tunable absorption and emission properties. These properties have distinguished Ge1-xSnx NCs as an intriguing material for near-infrared (IR) optical studies. Achieving a material with efficient visible emission requires a modified class of Group IV alloys and the computational studies suggest that this can be achieved with Ge1-x-ySiySnx NCs. Herein, we report a colloidal strategy for the synthesis of bulk-like (10.3 ± 2.5 – 25.5 ± 5.3 nm) and quantum-confined (3.2 ± 0.6 – 4.2 ± 1.1 nm) Ge1-x-ySiySnx alloys that show strong size confinement effects and composition-tunable visible to near IR absorption and emission properties. This synthesis produces a homogeneous alloy with diamond cubic Ge structure and tunable Si (0.9 – 16.1%) and Sn (1.8 – 14.9%) compositions, exceeding the equilibrium solubility of Sn (<1%) in crystalline Si and Ge. Raman spectra of Ge1-x-ySiySnx alloys show a prominent redshift of the Ge-Ge peak and the emergence of a Ge-Si peak with increasing Si/Sn, suggesting the growth of homogeneous alloys. The smaller Ge1-x-ySiySnx NCs exhibit absorption onsets from 1.21 to 1.94 eV for x = 1.8 – 6.8% and y = 0.9 – 16.1% compositions, which are blueshifted from those reported for Ge1-x-ySiySnx bulk alloy films and Ge1-xSnx alloy NCs, indicating the influence of Si incorporation and strong size confinement effects. Solid-state photoluminescence (PL) spectra reveal core-related PL maxima from 1.77 – 1.97 eV in agreement with absorption onsets, consistent with the energy gaps calculated for ~3–4 nm alloy NCs. With facile low-temperature solution synthesis and direct control over physical properties, this methodology presents a noteworthy advancement in the synthesis of bulk-like and quantum-confined Ge1-x-ySiySnx alloys as versatile materials for future optical and electronic studies.