Fig. 2. The PL characteristics of Cs₂AgBiBr₆ SC and PC films.

(A) Schematic of the phonon-assisted transitions at the indirect band edge for a typical indirect semiconductor. VB, valence band; CB, conduction band; Egd, direct band gap; Egi, indirect band gap. (B) Carrier density–dependent initial PL intensity of Cs₂AgBiBr₆ SC with 530-nm excitation. (C) The PLQYs of Cs₂AgBiBr₆ SC and PC film. The SC was excited using 532-nm (blue) and 473-nm (green) lasers at room temperature (RT). The PC film was excited using a 473-nm laser. (D) Fluence-dependent PL decays of Cs₂AgBiBr₆ SC upon 530-nm laser excitation. (E) Excitation energy–dependent PL kinetics of Cs₂AgBiBr₆ SC. Lines: Fitted curves with the model in the main text. (F) Temperature-dependent PL linewidth of Cs₂AgBiBr₆ SC. Dashed line, fitting with the conventional model for weak coupling; solid line, fitting with the model proposed by Toyozawa (39) for strong coupling.