Extended Data Fig. 3: Steady-state thermoelectric device cooling response, material properties, and figures of merit.
a, All three of the TEC devices remained stable and did not deviate once reaching the target temperature value. Differences in current used, compared to Fig. 2g, is because the input current to reach a target temperature can vary ±0.1 A across modules. b, Steady-state response of the thin-film module used with participant A1 for the cold object identification experiments. c, The figure of merit (ZT) was estimated using the Harman method to measure Ohmic (Vr) and Peltier (V0) voltage components when TEC device input current was switched off. d, Measured voltage values for each TEC device used to estimate the ZT. e, VT was estimated as the voltage at steady state before current was switched off (t0) and V0 was estimated by the voltage immediately after input current is removed. Measurements were taken at T = 300 K. f, Effective ZT estimated from thermal efficiency for thin-film (1 × 4 array) and bulk thermoelectric generator (TEG) devices. Data redrawn with permission from25. g, Inherent material properties of both p- and n-type materials were nominally the same in TFTEC modules and generally the same approach of comparable p- and n-type material properties are used by manufacturers of bulk modules65. Despite having a smaller active aspect ratio compared to bulkHC, the thin-film device has larger ZT and a slightly higher Seebeck coefficient, which leads to higher Peltier cooling. The material ZT were calculated from the three individual properties (that is, electrical resistivity, Seebeck coefficient and thermal conductivity) at T = 300 K. The observed module ZT of the CHESS TFTEC device is higher than both bulk devices – translating to less energy consumed in the cooling sensation in the present study and higher heat-to-electric conversion efficiency in a related study25.
