Phase transformation reaction path during sonication assisted solid state synthesis of Cu2ZnSnSe4

SEM micrographs of CZTSe sample: (a) as sonicated, (b) annealed at 300 °C, (c) annealed at 400 °C, (d) annealed at 450 °C, (e) annealed at 500 °C, (f) annealed at 600 °C.