Strain‐Tunable Band Alignment and Photoelectric Properties of CaAl 2 S 4 /InGaSe 2 van der Waals Heterostructure

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Hexagonal α 1 ‐CaAl 2 S 4 and Janus α 1 ‐InGaSe 2 , featuring unique physical and chemical attributes, stand out as exceptional contenders for optoelectronic implementations. However, on account of weak absorption of visible and UV light, α 1 ‐CaAl 2 S 4 faces limitations in optoelectronic device applications. Constructing a heterojunction with α 1 ‐CaAl 2 S 4 and α 1 ‐InGaSe 2 can significantly enhance photon absorption in both the visible and UV domains. This research employs first‐principles simulations to scrutinize the optical and electrical properties of α 1 ‐CaAl 2 S 4 , α 1 ‐InGaSe 2 , and the heterojunctions formed by these two materials. The output of the calculations shows that CaAl 2 S 4 /InGaSe 2 heterojunction demonstrates a remarkable enhancement with respect to light collection efficiency across the visible and UV span. The CaAl 2 S 4 /InGaSe 2 heterojunctions with different stacking structures exhibit type‐I and type‐II alignment modes, respectively. Furthermore, the bandgap value and type of heterojunctions can be effectively controlled by modulating the interlayer spacing and applying biaxial strain, resulting in a variety of band alignments and light absorption properties. These findings provide new material options and technological pathways for developing high‐efficiency photovoltaic cells, photoresponsive devices, solid‐state lighting elements, and novel photocatalytic and integrated optoelectronic devices.

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