Thermocouple is a material (junction between two different metals) which generates potential difference in terms of millivolts, isn't it?
Why don't we create a matrix of thermocouples (many thermocouples which are connected in series and parallel) to generate voltage in terms of volts or even kilovolts, and can supply current in terms of amperes?
Today's scientist are able to put billions of transistors inside a tiny chip. Why don't they put billions of thermocouples on a one meter-square plate? Isn't that feasible; if so, why? If it is feasible, just why don't they do it?