NOVELTY - A thermoelectric conversion element comprises electrode (13), thermoelectric conversion layer (14), and electrode (15) on a base material (12,16). The thermoelectric conversion layer contains thermally-stimulated polymer compound comprising nano-conductive material having mean long axis length of 5 nm or more, and cyclopentadiene-type repeating unit (I).    USE - Thermoelectric conversion element is used for article for thermoelectric generation and power supply for sensor (all claimed). Uses include but are not limited to hot spring heat generator, solar thermal power generation machine, waste-heat generator, power supply for wristwatch and semiconductor drive power supply.    ADVANTAGE - The thermoelectric conversion element has excellent thermoelectric conversion performance. The thermoelectric conversion material has excellent dispersibility with respect to nano-conductive material.    DETAILED DESCRIPTION - A thermoelectric conversion element comprises electrode (13), thermoelectric conversion layer, and electrode (15) on a base material. The thermoelectric conversion layer contains thermally-stimulated polymer compound comprising nano-conductive material having mean long axis length of 5 nm or more, and cyclopentadiene-type repeating unit of formula (I).    ring A=conjugated hydrocarbyl or conjugated heterocyclyl;    X=group in which one or more atoms chosen from C, O, S, N and P or Si are used as a ring-constituent atom of ring A;    R11,R12=substituent;and    or R11+R12=optionally ring.    The mean inter-unit distance of the ring A is 1.42 Angstrom or less. An INDEPENDENT CLAIM is included for thermoelectric conversion material for forming thermoelectric conversion layer, which contains thermally-stimulated polymer compound comprising nano-conductive material with mean long axis length of 5 nm or more and cyclopentadiene-type repeating unit (I).    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the thermoelectric conversion element. (Drawing includes non-English language text)    Metal plates (11,17)    Base materials (12,16)    Electrodes (13,15)    Thermoelectric conversion layer (14)