Hot carrier cooling in lead halide perovskites probed by two-pulse photovoltage correlation spectroscopy

The next-generation hot-carrier solar cells, which can overcome the Shockley-Queisser limit by harvesting excess energy from hot carriers, are receiving increasing attention. Lead halide perovskite (LHP) materials are considered as promising candidates due to their exceptional photovoltaic properties, good stability and low cost. The cooling rate of hot carriers is a key parameter influencing the performance of hot-carrier solar cells. In this work, we successfully detected hot carrier dynamics in operando LHP devices using the two-pulse photovoltage correlation technique. To enhance the signal-to-noise ratio, we applied the delay-time modulation method instead of the traditional power modulation. This advancement allowed us to detect the intraband hot carrier cooling time for the organic LHP CH3NH3PbBr3, which is as short as 0.21 ps. In comparison, the inorganic Cs-based LHP CsPbBr3 exhibited a longer cooling time of around 0.59 ps due to different phonon contributions. These results provide us new insights into the optimal design of hot-carrier solar cells and highlight the potential of LHP materials in advancing solar cell technology.