Solution-processed Ge(ii)-based chalcogenide thin films with tunable bandgaps for photovoltaics

Abstract

Solution processes have been widely used to construct chalcogenide-based thin-film optoelectronic and electronic devices that combine high performance with low-cost manufacturing. However, Ge (II)-based chalcogenide thin films possessing great potential...

Composition Dependence of the Band Gaps of Semiconducting GeSxSe1–x van der Waals Alloys

“…Solution-processed thick polycrystalline GeS x Se 1−x films with three different compositions were fabricated and found to show some bowing (b = 0.15 eV) as determined from optical absorption measurements. 33 In another work, DFT calculations predicted a change from a direct to an indirect gap for GeS x Se 1−x alloys with x = 0.7, and a substantial deviation from a linear E g (x) behavior toward the GeSe endpoint. 34 The experimental determination of the band gaps, however, found a linear E g (x) but showed a significant discrepancy between absorption and photoluminescence (PL) measurements that could be performed only for one alloy composition.…”

“…Experimental results regarding the band gaps are so far sparse and inconsistent. Solution-processed thick polycrystalline GeS x Se 1– x films with three different compositions were fabricated and found to show some bowing ( b = 0.15 eV) as determined from optical absorption measurements . In another work, DFT calculations predicted a change from a direct to an indirect gap for GeS x Se 1– x alloys with x = 0.7, and a substantial deviation from a linear E g ( x ) behavior toward the GeSe endpoint .…”

Review of Nanolayered Post-transition Metal Monochalcogenides: Synthesis, Properties, and Applications

“…39 These predictions were experimentally confirmed by multiple groups: GeS and α-GeSe have been shown to be p-type semiconductors with band gaps around 1.55−1.71 eV and 1.1−1.53 eV, respectively. 42,43,157,158 The ternary compound GeSe 1−x S x showed excellent band gap tuning from 1.14 to 1.71 eV as the composition varied from x = 0 to x = 1. 158 Band diagrams for the single layers of GeS and α-GeSe are depicted in Figure 12a,b, respectively.…”

“…42,43,157,158 The ternary compound GeSe 1−x S x showed excellent band gap tuning from 1.14 to 1.71 eV as the composition varied from x = 0 to x = 1. 158 Band diagrams for the single layers of GeS and α-GeSe are depicted in Figure 12a,b, respectively. Bulk GeS remains an indirect semiconductor with an established band gap of 1.56 eV, whereas reported direct and indirect band gaps of bulk α-GeSe range from 0.8−1.54 eV at room temperature.…”

Intricate Reaction Pathways on CH3NH3PbI3 Photocatalysts in Aqueous Solution Unraveled by Single-Particle Spectroscopy

“…The molar ratio of I − :H 3 PO 2 in the solution was 3.3:1.0. Considering the pK a values of HI (−10) and H 3 PO 2 (1.23) 42 and the pH of the solution (approximately −0.7), the H 3 PO 2 was almost fully protonated. Therefore, I − ions were preferentially adsorbed on the cationic sites on the surface of the MAPbI 3 because of electrostatic interactions, which effectively captured holes.…”