Fig. 3: Principle analysis of WSe₂/H₂O/PdSe₂ UTPB devices.

a Simulated energy band diagram of the device under different V_ds conditions, where WSe₂, polarized water, and PdSe₂ serve as the contact layer, UTPB, and absorber, respectively. The horizontal dashed line represents the heterojunction Fermi level. The black arrows represent the direction of the polarization field of interlayer water. b Arrhenius fitting of the dark current for WSe₂/H₂O/PdSe₂ devices. Inset: Arrhenius fitting of the dark current for WSe₂/PdSe₂ devices. The dark current of the H₂O device remains low and temperature-independent, demonstrating high-operating-temperature features at room temperature and even higher temperatures. The vertical dashed line represents the location of 300 K (room temperature). These data are extracted from Supplementary Fig. 9. c Arrhenius fitting of the photocurrent for WSe₂/H₂O/PdSe₂ and WSe₂/6L-hBN/PdSe₂ devices. The WSe₂/6L-hBN/PdSe₂ device follows a thermal emission model, as expressed in the equation of the inset, where J is the current density, A is the Richardson constant, T is the temperature, \({\varphi }_{b}\) is the barrier height, and k_B is the Boltzmann constant. The photocurrent of the H₂O device remains stable across temperatures, indicating compliance with the direct tunneling (DT) mode. The vertical dashed line represents the location of 300 K (room temperature). This data is extracted from Supplementary Fig. 10. d, e DFT-calculated interlayer potential difference and charge transfer efficiency for WSe₂/PdSe₂ (d) and WSe₂/H₂O/PdSe₂ (e) structures. Polarized water increases the interlayer potential difference and enhances electron transfer within the heterojunction. The arrows represent the direction of electron transfer within the heterojunction. f Schematic band diagram illustrating the interlayer potential difference and WSe₂ depletion state with/without polarized water. Polarized water generates a larger interlayer potential difference, completely depleting electrons in WSe₂, with the Fermi level approaching the valence band edge. I_Diff., diffusion current; I_G-R, generation-recombination current; I_Back., background current; DT model, direct tunneling mode; TE model, thermal emission mode. DFT, density functional theory.