Polarization Photoelectric Conversion in Layered GeS

Abstract Polarization photovoltaic effect is a unique character for an energy material with specific in‐plane anisotropy. Especially, if the energy material has a direct bandgap close to 1.6 eV, it will efficiently absorb full sunlight spectrum with specific axial polarization. In this study, polarized microtransmittance measurements of GeS multilayer with polarization angles ranging from θ = 0° (E || a) [through 90° (E || b)] to θ = 180° (E || a) have been studied near band edge. The polarized absorption edge follows a sinusoidal variation of E(θ) = 1.6 + 0.05⋅|sin(θ)| eV with respect to the angle change of the polarized absorption spectra. This anisotropic optical response is well reproduced by first‐principles calculations based on a combined Green's function technique, the GW–Bethe–Salpeter equation (BSE) approach. To characterize highly anisotropic band structure of layered GeS, polarized thermoreflectance measurement and first‐principles quasiparticle band‐structure calculations are also carried out. The interband transitions belonging to E ||a and E ||b polarizations are respectively identified. The polarized surface photovoltaic effects of a GeS Schottky solar cell are also tested. The special in‐plane optical anisotropy (along a and perpendicular to the a axis) renders GeS owning highly bi‐axial responsivity with respect to the c‐plane photoelectric conversion.