Investigation of Physical and Electronic Properties of GeSe for Photovoltaic Applications

Advanced Optical Materials

Liu

Wang

et al. 2018

Self Cite

As a new member of 2D materials, GeSe has attracted considerable attention recently due to its fascinating in-plane anisotropic vibrational, electrical, and optical properties originating from the low-symmetry crystal structure. Among these anisotropic properties, the anisotropic optical property, as a new degree of freedom to manipulate optoelectronic properties in 2D materials, is of great importance for practical applications. However, the fundamental understanding of the optical anisotropy of GeSe is still under exploration, severely restricting its utility in polarization-sensitive optical systems. Here, a systematic study about the in-plane optical anisotropy of GeSe is reported, including its anisotropic optical absorption, reflection, extinction, and refraction. The anisotropic band structure of GeSe is experimentally observed for the first time through angle-resolved photoemission spectroscopy, explaining the origin of the optical anisotropy. The anisotropic reflection and refraction of GeSe are further directly visualized through the angle-dependent optical contrast of GeSe flakes by azimuth-dependent reflectance difference microscopy and polarization-resolved optical microscopy, respectively. Finally, GeSe-based photodetectors exhibit a polarization-sensitive photoresponsivity due to the intrinsic linear dichroism. This study provides fundamental information for the optical anisotropy of GeSe, forcefully stimulating the exploration of novel GeSe-based optical and optoelectronic applications.

Section: Resultssupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

In‐Plane Optical Anisotropy of Low‐Symmetry 2D GeSe

Advanced Optical Materials

Liu

Wang

et al. 2018

Self Cite

“…Consequently, SWNT films, which exhibit full solar spectrum absorption capability, are considered as ideal candidates of ultrathin photothermal material for efficient solar steam generation. More importantly, the SWNT film with porous network structure and superior mechanical strength shows great potential to combine with other photothermal materials such as MoS 2 , noble metal nanoparticles, PPy, graphene, or solar energy harvesting films to obtain a hybrid solar steam generation film with synergistic photothermal properties.…”

Section: Introductionmentioning

confidence: 91%

An Ultrathin Flexible 2D Membrane Based on Single‐Walled Nanotube–MoS₂ Hybrid Film for High‐Performance Solar Steam Generation

et al. 2017

Adv Funct Materials

299

206

Solar steam generation is achieved by localized heating system using various floating photothermal materials. However, the steam generation efficiency is hindered by the difficulty in obtaining a photothermal material with ultrathin structure yet sufficient solar spectrum absorption capability. Herein, for the first time, an ultrathin 2D porous photothermal film based on MoS 2 nanosheets and single-walled nanotube (SWNT) films is prepared. The as-prepared SWNT-MoS 2 film exhibits an absorption of more than 82% over the whole solar spectrum range even with an ultrathin thickness of ≈120 nm. Moreover, the SWNT-MoS 2 film floating on the water surface can generate a sharp temperature gradient due to the localized heat confinement effect. Meanwhile, the ultrathin and porous structure effectively facilitates the fast water vapor escaping, consequently an impressively high evaporation efficiency of 91.5% is achieved. Additionally, the superior mechanical strength of the SWNT-MoS 2 film enables the film to be reused for atleast 20 solar illumination cycles and maintains stable water productivity as well as high salt rejection performance. This rational designed hybrid architecture provides a novel strategy for constructing 2D-based nanomaterials for solar energy harvesting, chemical separation, and related technologies.

“…As a member of group‐IV monochalcogenides, GeSe has been considered as a promising absorber material for photovoltaic applications due to its attractive optical and electrical properties as well as earth‐abundant and low‐toxic constituents . Recently, GeSe solar cell with an efficiency of 1.48% fabricated through self‐regulated rapid thermal sublimation (RTS) was first reported by our group, demonstrating the potential of GeSe for solar cells.…”

mentioning

confidence: 99%

“…Bandgaps of our four samples were further estimated by plotting ( αhν ) 1/2 versus ( hν ), where α is the absorption coefficient shown in Figure S8, Supporting Information (calculated based on the simplified formula: α = d −1 ln( T −1 ), where T is the transmittance and d is the thickness of GeSe film, identical to the thickness in Figure S7, Supporting Information) and hν is the photon energy, as shown in Figure b. The bandgap of as‐prepared amorphous GeSe film was found to be 1.79 eV, while the bandgap of the sample annealed at 500 °C was about 1.14 eV, in good agreement with the values from literatures and our previous reports . It was noteworthy that GeSe films annealed at 350 and 400 °C with corresponding GeSe nanosheets thickness of 2.5 and 4.5 nm showed bandgaps of 1.44 and 1.20 eV, respectively.…”

mentioning

confidence: 99%

Tuning the Optical Absorption Property of GeSe Thin Films by Annealing Treatment

Liu

Physica Rapid Research Ltrs

Zhang

et al. 2018

As an emerging promising photovoltaic absorber material, GeSe has attracted significant interest recently due to its simple binary composition, attractive optical and electrical properties as well as earth‐abundant and low‐toxic constituents. However, no systematic study on the absorption property tuning of GeSe has been reported. Here, first it is shown that the crystallization temperature of amorphous GeSe is about 330 °C through differential thermal analysis and temperature‐dependent X‐ray diffraction. Next, GeSe films with tunable absorption property in the range of 1.79–1.14 eV are fabricated by annealing amorphous GeSe films at different temperatures. Finally, through the combined analysis of bandgaps measured by transmission spectroscopy and nanosheet thickness characterized by cross‐sectional high‐resolution transmission electron microscopy, the blue shift of bandgap with decreasing thickness of nanosheets has been attributed to the quantum confinement effect. Such continuously tunable absorption property of GeSe films makes it more useful for further optoelectronics.