Diamond-like carbon based thermoelectric conversion devices and methods of making and using the same which have improved conversion efficiencies and increased reliability. The device can include a cathode having a base member with a layer of diamond-like carbon material such as amorphous diamond coated over the cathode. A dielectric intermediate member can be electrically coupled between the diamond-like carbon material and an anode. Various additional layers and configurations can allow for improved performance such as multiple cathode layers and/or multiple intermediate layers. The thermoelectric conversion devices can be configured as an electrical generator and/or a cooling device and can be conveniently formed. In addition, the devices of the present invention do not require formation of a vacuum space and are typically completely solid throughout. As a result, the devices of the present invention are susceptible of mass production at reduced costs and have improved conversion efficiencies and reliability.