Piezoelectric Photoacoustic Spectra of Bulk CuIn3Se5 Crystals Grown by the Traveling Heater Method

The piezoelectric photoacoustic (PPA) spectra of bulk Cufrı₃Se₅ crystals grown by a traveling heater method (THM) were measured at room and liquid nitrogen temperatures. The bandgap energy of the bulk CuIn₃Se₅ crystals at room temperature is estimated to be 1.25 ± 0.02 eV. We also obtained PPA peaks of three types of non-radiative centers in the bulk CuIn₃Se₅ crystals for the first time. The activation energies of three possible intrinsic defect levels are estimted to be 0.32 ± 0.02, 0.25 ± 0.02 and 0.15 ± 0.02 eV.