Abstract
Palladium selenides have attracted considerable attention because of their intriguing properties and wide applications. Motivated by the successful synthesis of Pd2Se3 monolayer (Lin et al., Phys. Rev. Lett., 2017, 119, 016101), here we systematically study its physical properties and device applications using state-of-the-art first principles calculations. We demonstrate that the Pd2Se3 monolayer has a desirable quasi-direct band gap (1.39 eV) for light absorption, a high electron mobility (140.4 cm2V−1s−1) and strong optical absorption (~105 cm−1) in the visible solar spectrum, showing a great potential for absorber material in ultrathin photovoltaic devices. Furthermore, its bandgap can be tuned by applying biaxial strain, changing from indirect to direct. Equally important, replacing Se with S results in a stable Pd2S3 monolayer that can form a type-II heterostructure with the Pd2Se3 monolayer by vertically stacking them together. The power conversion efficiency (PCE) of the heterostructure-based solar cell reaches 20%, higher than that of MoS2/MoSe2 solar cell. Our study would motivate experimental efforts in achieving Pd2Se3 monolayer-based heterostructures for new efficient photovoltaic devices.
Highlights
We noticed that in Reference [24] the results were obtained from standard density functional theory (DFT) calculations (the Perdew-Burke-Ernzerhof (PBE) functional [27] for the generalized gradient approximation (GGA)), which is well-known to underestimate the electronic band gap of semiconductors
The hybrid functional that combines standard DFT with Hartree-Fock (HF) calculations has been widely used for calculating the band gaps, because it predicts more reliable physical properties and keeps a good compromise with computational efficiency
The dominant source of electron scattering is from acoustic phonons and the carrier mobility can be obtained using deformation potential theory proposed by Bardeen and Shockley [35], which has been successfully employed in many 2D materials [36,37,38,39]
Summary
Two-dimensional (2D) transition metal chalcogenides (TMCs), including semiconducting MoS2 [1], MoSe2 [2], WS2 [3], WSe2 [4], ReS2 [5], PtS2 [6], PdSe2 [7,8], and metallic VS2 [9] and NbS2 [10] are of current interest because of their extraordinary properties and practical applications in catalysis [11], electronics [12,13,14], optoelectronics [15,16] and valleytronics [17,18]. We use the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional [28,29] to study the electronic, transport and optical properties of the newly synthesized Pd2Se3 monolayer. We show that this monolayer possesses a desirable bandgap for light harvesting, offering better opportunity for photovoltaic applications. The heterostructure-based solar cell can reach a high power conversion efficiency (PCE) of 20% These fascinating properties make the Pd2Se3 monolayer a promising candidate for future applications in nanoscale electronics and photonics
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