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The efficiency of conventional single-junction solar cells is fundamentally limited by the Shockley–Queisser (SQ) limit, arising primarily from rapid carrier thermalization. Hot-carrier solar cells (HCSCs) offer a pathway to surpassing this limit by extracting photogenerated carriers before they equilibrate with the lattice. Realizing this concept requires absorber materials that slow hot-carrier cooling and device architectures incorporating energy-selective contacts. In this work, we present theoretical methods based on first-principles-informed ensemble Monte Carlo simulations of the Boltzmann transport equation to compare hot-carrier dynamics across two contrasting absorber platforms: metal halide perovskites (MHPs) and III–V multi-quantum wells (MQWs). Our simulations quantitatively confirm the hot-phonon bottleneck (HPB) as the dominant slow-cooling mechanism in MHPs, reveal the detrimental role of cold background carriers, and highlight compositional tuning as a key design lever. For III–V MQWs, we validate phonon engineering as an effective strategy to extend LO-phonon lifetimes, reproducing experimental hot-carrier behavior in InAs/AlAsSb superlattices. Synthesizing insights across these material classes, we distill general design principles emphasizing phonon management, the elimination of thermal sinks, and the leveraging of spatial confinement. These findings establish a quantitative basis for rational absorber design and point toward hybrid material strategies capable of breaking the SQ efficiency limit.
Filipovic et al. (Mon,) studied this question.