Phase formation, morphology evolution and tunable bandgap of Sn1−xSbxSe nanocrystals

Abstract

The phase formation, morphology evolution and bandgap of Sn_1−xSb_xSe (0 ≤ x ≤ 0.6) nanocrystals synthesized at 230–275 °C for 5–36 h in a one-pot system were studied. Sn²⁺ is kinetically more reactive than Sb³⁺ toward Se²⁻. The SnSe(1) phase (JCPDS 01-075-6133) grew in the Sn_1−xSb_xSe (0 ≤ x ≤ 0.2) nanocrystals, while the SnSe(2) phase (JCPDS 32-1382) was dominant in the Sn_1−xSb_xSe (0.3 ≤ x ≤ 0.6) nanocrystals. In the present study, the substitution solubility of Sb in the SnSe lattice is about 10 at%. The introduction of more Sb in the Sn_1−xSb_xSe (0.3 ≤ x ≤ 0.6) nanocrystals induced more defects therein and thus caused the phase transformation from SnSe(1) to SnSe(2). The SnSe nanocrystals grew as nanosheets, while the introduction of Sb enhanced the growth of Sn_1−xSb_xSe nanorods. The direct and indirect bandgaps of the Sn_1−xSb_xSe (0 ≤ x ≤ 0.2) nanocrystals could be tuned from 1.39 to 1.53 eV and 0.93 to 1.28 eV, respectively, by increasing the Sb concentration (x) from 0 to 0.2. The tunable morphology and bandgap of the Sn_1−xSb_xSe nanocrystals make them potential candidates as photovoltaic materials.