Carrier Cooling in Lead Halide Perovskites: A Perspective on Hot Carrier Solar Cells

The concept of hot carrier solar cells (HCSCs) has been proposed as a promising yet elusive path toward high-performance photovoltaics (PV), capable of surpassing the Shockley–Queisser limit by recycling energy that would otherwise be lost during thermalization. Lead halide perovskites (LHPs) have emerged as highly promising materials for PV applications. The reports of slow hot carrier (HC) cooling in these materials have ignited discussions of their potential in realizing HCSCs. Here we summarize the key findings regarding HC dynamics in LHPs, as revealed by numerous studies using advanced time-resolved spectroscopies. We also emphasize the interconnected mechanisms involved in HC cooling. In addition, we discuss the influence of nanostructuring on HC cooling dynamics in LHPs and suggest that two-dimensional LHPs, with their inherent quantum well structure, might exhibit modified phononic features and altered carrier–phonon coupling strength. We conclude by critically discussing the prospects for HCSCs, taking into account our current understanding of HC cooling and excitation conditions under sunlight.