Enhanced thermoelectric performance and tunable polarity in 2D Cu2S-phenol superlattices composites for solar energy conversion

Solar energy conversion is of great interest in developing green and sustainable energy. Herein, we report the solar-to-electricity capability of a new two dimensional (2D) Cu2S-phenol superlattice (CP-SL) and carbon nanotubes (CNTs) composites for the first time. CP-SL is demonstrated to have a high Seebeck coefficient and a low thermal conductivity comparable to that of metal-organic frameworks. CP-SL based solar thermoelectric generator (STEG) exhibits stable output voltages for long time usages superior to previously reported STEGs. The device is made of p- and n-type modules that are composed of CP-SL/CNT and CP-SL/polyethyleneimine (PEI) doped CNTs (PEI-CNT) composites, respectively. The polarity of the composites is dominated by the CNTs which have higher carrier concentration. The carrier transport mechanism in the composites matches well with a parallel model, indicating the CP-SL and CNT interfaces play a minor role in carrier transport. The maximum ZT value of CP-SL/CNT is achieved by an in-situ growth method, which is about 35 times higher than that of the original CP-SL. These results indicate that 2D CP-SL is a new material with tunable thermoelectric properties and polarities, which may lay a foundation to realize p- and n-type properties in one material for single-material organic electronic devices development.