[15a-E402-1~11] 12.4 Organic light-emitting devices and organic transistors

▲ [15a-E402-2] Enhanced Hot-Phonon Bottleneck Effect on Slowing Hot Carrier Cooling in Metal Halide Perovskite Quantum Dots With Alloyed A-Site

〇(D)Hua Li¹, Dong Liu¹, Chao Ding¹, Shuzi Hayase¹, Qing Shen¹ (1.Univ. of Electro-Communications)

Keywords:Perovskite quantum dots, A-site cations cross-exchange, Hot carrier

Halide perovskite quantum dots (PQDs) with the general formula APbX₃ (X = Cl^-, Br^-, and I^-), where A is a cation such as cesium (Cs⁺), methylammonium (MA⁺, CH₃NH₃⁺), or formamidinium (FA⁺, CH(NH₂)²⁺), have recently emerged as a promising material for many applications, such as solar cells and light-emitting diodes. A deeply understanding of how the A-site cations cross-exchange affects the hot carrier relaxation dynamics in PQDs has a profound implication for further developing the disruptive hot carrier solar cells (HCSCs). However, it has yet to be experimentally studied so far. Here, we investigate the hot carrier cooling kinetics in pure FAPbI₃, CsPbI₃ and the alloyed FA_0.5Cs_0.5PbI₃ QDs by using ultrafast transient absorption (TA) spectroscopy in combination with temperature-dependent PL and the first principles calculations method. It is demonstrated that the lifetime of initial fast cooling stage (<1 ps) for all organic cation-containing PQDs are shorter than inorganic CsPbI₃ QDs, which is ascribed to the strong coupling of electron-phonon due to the motion of organic cation, this is verified by the strength of electron-phonon extracted from temperature-dependent PL. Surprisingly, we find that the slow stage cooling lifetime in alloyed PQDs is significantly extended under higher excitation intensity attributed to the interplay of hot-phonon bottle effect and efficient acoustic phonon up-conversion that can be supported by the first principles calculations.