FABRICATION OF Cs2TeI6 FILM BY ANNEALING CsI FILM IN TeI4 VAPOUR: EFFECT OF ANNEALING TEMPERATURE

Halide perovskites are now considered promising materials in the field of optoelectronic devices. Recently, the double halide-perovskite cesium tellurium iodine Cs2TeI6 has shown its potential application due to its strong stability, high absorption coefficient, suitable bandgap and composition of non-toxic elements. However, studies on its experimental fabrications are still limited. In previous works, we reported a method for fabricating Cs2TeI6 thin films by a synthesis of a CsI film followed by annealing in TeI4 vapor. Those studies focused more on application orientation rather than in-depth analysis of the influence of technical parameters on the film formation. In this study, we make CsI films by using the chemical vapor deposition method and then investigate the effect of TeI4-annealing temperature in the range of 120-330ºC on the Cs2TeI6 film formation. After that, the optical property and long-term stability are examined. At 240ºC, the film is black, tightly packed and pin-hole free with a good adhesion with the substrate. It has high absorbance in the visible region with an optical bandgap of 1.61 eV and the film is found to be very stable in humid air for 20 weeks.