  Thermoelectric materials traditionally incorporate heavy metals to achieve
low lattice thermal conductivity. However, elements such as Te, Bi, and Pb are
costly and pose environmental hazards. In this study, we introduce a novel
design strategy for thermoelectric materials, focusing on room-temperature,
light-element, and high-ZT materials such as coronene-cyclobutadienoid graphene
nanoribbons (cor4GNRs). This material demonstrates a ZT value exceeding 2.1,
attributed to its exceptionally low phonon thermal conductivity resulting from
its unique edge structure. Importantly, its electrical conductance and Seebeck
coefficient remain relatively high and nearly unaffected by the edge structure.
This distinct behavior in phonon and electronic transport properties leads to a
remarkably high ZT value. Additionally, we discover that applying strain can
significantly reduce phonon thermal conductivity, potentially increasing the ZT
value to over 3.0. Our findings provide innovative insights for the design and
application of advanced thermoelectric materials.
