Giant polarization ripple in transverse pyroelectricity

Abstract

Pyroelectricity originates from spontaneous polarization variation, promising in omnipresent non-static thermodynamic energy harvesting. Particularly, changing spontaneous polarization via out-of-plane uniform heat perturbations has been shown in solar pyroelectrics. However, these approaches present unequivocal inefficiency due to spatially coupled low temperature change and duration along the longitudinal direction. Here we demonstrate unconventional giant polarization ripples in transverse pyroelectrics, without increasing the total energy input, into electricity with an efficiency of 5-fold of conventional longitudinal counterparts. The non-uniform graded temperature variation arises from decoupled heat localization and propagation, leading to anomalous in-plane heat perturbation (29-fold) and enhanced thermal disequilibrium effects. This in turn triggers an augmented polarization ripple, fundamentally enabling unprecedented electricity generation performance. Notably, the device generates a power density of 38 mW m^-2 at 1 sun illumination, which is competitive with solar thermoelectrics and ferrophotovoltaics. Our findings provide a viable paradigm, not only for universal practical pyroelectric heat harvesting but for flexible manipulation of transverse heat transfer towards sustainable energy harvesting and management.

Fig. 1. The conceptual mechanistic of TPG in comparison with a conventional device.

a Schematic depiction of conventional (CONV) pyroelectric device. b Schematic illustration of TPG. M = A/a stands for the magnification of low-grade solar heat localization for TPG surface area (A) compared with irradiation area (a), where E = ME’, I > I’, ΔP > ΔP’, θ₁ > θ’ > θ₃, Q > Q’, dT/dt > dT’/dt’ and t > t’. The polarization follows the direction of temporal temperature variations. c Normalized output for conventional (back, M = 1) and TPG devices under different irradiation intensities and magnifications.

Fig. 2. Identification of temperature-driven polarization ripple in transverse pyroelectricity.

a Temperature profiles of a single conventional (stripe) and TPG devices. The upper and lower dashed lines refer to the maximum and half maximum temperatures of the TPG device. FWHM stands for the full width at half maximum of the temperature distribution. b, c Measured spatiotemporal temperatures (b) and polarization ripples (c) of TPG device. d The absolute current response for conventional (blue lines) and TPG (red lines) devices. The dashed line marks the maximum amplitude of absolute current for the conventional device. e The voltage response of a single conventional and TPG device. The time-differential voltage indicates the temperature-dependent voltage dynamics under the rising, saturation, falling, and decay stages. f The voltage varies with charge, and harvested energy (integration as shown in the shadow area) of a single conventional (stripe) and TPG devices, where W > W’ indicates the harvested energy of TPG is greater than that of conventional device. The dashed line masks zero voltage at thermal equilibrium, and the equivalent voltage relative to the cooling stage is negative, specifying the voltage consumption/decrease shown in Fig. 2e and Supplementary Fig. 7. The illumination intensity for measurement is 0.1 sun.

Fig. 3. Finite element analysis and experimental verification.

a–c Simulation profiles of in-plane conductive heat flux (a), temporal temperature variation (b), and polarization (c) for conventional (upper rows) and TPG (bottom rows) devices. Scale bar: 10 mm. d Enhancement ratio of TPG/conventional devices estimated from simulation profiles. The dashed line specifies 1.0 for the ratio of TPG/conventional devices. e Output voltage (the left two columns) and current (the right two columns) of conventional and TPG devices. The experimental and simulated incident illumination intensities are fixed at 0.1 sun. f Gain factor of conventional and TPG devices under cooling/heating measurements. The dashed line marks 1.0 for a typical device at consistent heating/cooling processes.

Fig. 4. Enhancement of rippled polarization and TPG output.

a, b Pyroelectric current (a) and voltage (b) of single conventional (M = 1) and TPG devices at various irradiation areas and solar intensities. c Temperature and pyroelectric coefficient synergistic manipulations from conventional to transverse (TPG) pyroelectrics for typical low-T_Curie (<100 °C) devices under heating/cooling variations. The coloured blocks indicate the operating temperature range for conventional and TPG devices at identical solar illuminations, respectively. d Current and voltage enlargement of single inorganic conventional and TPG devices at 0.1 sun. PMN_0.7PT_0.3, 0.7Pb(Mg_1/3Nb_2/3)O₃−0.3PbTiO₃; PZT, Pb(Ti,Zr)O₃. e Polarization enhancement ratio versus conventional design (left, P_S/P_S@CONV) and polarization in the device area and illuminated area (right, P_S@A/P_S@a).

Fig. 5. Scalable TPG systems and comparison of power output with conventional devices.

a The output power for modular conventional (upper right) and TPG (lower right) systems, in series and parallel mode under 0.1 sun. Scale bar: 5 cm. b Harvested charge measurement of TPG under 1000 heating/cooling cycles. Inset, the first and last five cycles. Q₀ stands for the initial measured peak charge, as shown in Supplementary Fig. 11f. c Comparison of peak power density for proposed TPG (solid scatters) and conventional devices at different solar illuminations. The dashed and dotted lines represent solar organic thermoelectric generation (SOTEG), and the solid lines refer to ferrophotovoltaics (FPV, orange region). d Historical view of volumetric power density for conventional devices and TPG results. Blue region: conventional devices. Details of power density comparison in (c) and (d) can be found in Supplementary Table 3.