Effect of structural phase transitions on the exciton absorption spectrum of thin CsPbCl3 films

The absorption spectrum of thin film CsPbCl3 in the 2–6 eV range is studied at temperatures of 90–500 K. Sudden changes show up in the temperature dependences of the parameters of the long-wavelength exciton band (spectral position Em(T), half width Γ(T), and oscillator strength f(T)) at the first order phase transitions at 310 and 320. No phase transitions in Em(T), Γ(T), and f(T) are detected at low temperatures. The exciton excitations in CsPbCl3 are found to have a three-dimensional character.