Prolonged hot carrier cooling induced by intra-band gaps in Dirac graphyne carbon allotropes†

Abstract

Understanding and controlling photoexcited carrier dynamics in light-harvesting materials is the key to unleashing the potential of next-generation solar cells. Two-dimensional Dirac cone materials are attractive as emergent absorbers because of their unusual optical adsorption and energy transport properties. However, rapid hot carrier cooling poses significant limitations on energy extraction. Here, we propose a hot carrier management strategy via arranging carbon atomic motifs. The effects of intra-band gaps on hot carrier dynamics in two-dimensional Dirac graphyne carbon allotropes are investigated through ab initio nonadiabatic molecular dynamics in momentum space. We reveal that the removal of momentum-conserving cooling pathways across an intra-band gap significantly weakens electron–phonon coupling behavior. The hot carrier cooling time constant is extended from 0.28 ps to 12.287 ps, indicating sufficiently prolonged hot carrier cooling properties. Our findings advance the fundamental knowledge of hot carrier dynamics in Dirac materials and highlight the excellent potential of intra-band gaps in efficient extraction of hot carriers, which is crucial for improving the performances of energy and photovoltaic devices.