An extremely high power factor in Seebeck effects based on a new n-type copper-based organic/inorganic hybrid C6H4NH2CuBr2I film with metal-like conductivity

Abstract

Organic/inorganic hybrid materials can be promising thermoelectric materials due to the possibilities of achieving high electrical conductivity and low thermal conductivity, which are necessary for their potential application in heat–electricity conversion. In this work, we show that the new n-type organic/inorganic hybrid C₆H₄NH₂CuBr₂I can simultaneously exhibit a high electrical conductivity of ∼3.6 × 10³ S cm⁻¹ and a Seebeck coefficient of ∼−70 μV K⁻¹ at room temperature in a thin-film design, presenting the highest power factor reaching 1740 μW mK⁻². The temperature dependence of both the electrical conductivity and Seebeck coefficient in this C₆H₄NH₂CuBr₂I film illustrates that this organic/inorganic hybrid film behaves like a metallic material. The high electrical conductivity of the C₆H₄NH₂CuBr₂I film can be attributed to the defect-related heavy doping caused by Cu^I in this semiconductor, while the relatively large Seebeck coefficient is due to the coexisting entropy difference and polarization difference. The temperature-dependent polarization difference between the hot and the cold side of the film can function as an additional driving force besides the entropy difference and contribute to the Seebeck effect development in C₆H₄NH₂CuBr₂I. When applying a temperature difference of 4.8 °C along the in-plane direction, the C₆H₄NH₂CuBr₂I film with gold contacts generates a thermoelectric voltage of −0.31 mV and a thermoelectric current of −0.022 mA, suggesting a promising n-type thermoelectric material for heat–electricity conversion in thermoelectric power generators.