Modulating carrier transport by cross-dimensional compositing of Ag2Se/MXene for high-performance flexible thermoelectrics

Abstract

Flexible thermoelectrics (TEs) offer immense potential for self-powering of wearable/implantable electronics. However, the trade-off between the flexibility and power factor of the materials has long been a challenge. Here, we report a nano-compositing strategy involving Ag₂Se nanowire matrix and MXene nanosheet filler to well address this issue. The as-prepared composite film has a cross-dimensional structure consisting of crystalline Ag₂Se grains and distinctive layered MXenes, which enables simultaneously rapid electron transport and high flexibility. The heterogeneous interfaces, pores and dislocations were attributed to enhanced carrier transport that favors the electrical conductivity. A film of such composite delivered a high power factor of 2125 μW m⁻¹ K⁻² at 300 K with only a 7% decrease in electrical conductivity after 3000 bending cycles, showing remarkable merits in both power conversion and flexibility. A six-leg TE generator constructed from the composite reached a maximum power density of 24.2 W m⁻² at a temperature difference of ∼31 K, which is among the highest reported values in film-based TE generators. The as-assembled devices also showed sufficiently fast response to allow for solar TEs and TE sensing in addition to conventional wearable/portable energy harvesting and cooling.