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Recently, double perovskite A2B(I)B′(III)X6 has attracted a huge amount of interest due to its wide application in the field of light detection. However, the biggest limitation in the pursuit of further developments in this area is the narrow detection range and the low carrier mobility. It is well known that the effective mean to overcome the above shortcomings is changing the B site ions of A2B(I)B′(III)X6 concentration for the double perovskite. In this study, we study the photoelectronic properties included atomic structure, electronic properties and optical properties of Cs2AgxCu1-xInyTb1-yCl6 (x = 0, 0.25, 0.5, 0.75, 1; y = 0, 0.25, 0.5, 0.75, 1) using first-principles methods. Besides, we systematically investigate carrier mobility of Cs2Ag0.75Cu0.25In0.75Tb0.25Cl6. The results demonstrate Cs2Ag0.75Cu0.25In0.75Tb0.25Cl6 is the most excellent photoelectronic performance with the narrow band gap reduced of 0.56 eV, compared with Cs2AgInCl6, broadening the light detection range. Moreover, the hole mobility is increased from 0.001 to 2.81 cm2 v−1 s−1, which promotes the separation of photogenerated carriers and enhance the photoelectron conversion efficiency. Our works demonstrate that the modification of metal concentration will modulate the optoelectronic performance properties of double perovskites, which provides a theoretical basis for the other double perovskites in potential infrared detection application.

Ferroelectricity is an important source of the fascinating optoelectronic properties of heterostructures. Interfaces formed between ferroelectrics and oxides or transition metal dichalcogenides have undergone rapid development. However, the integration of ferroelectrics and two-dimensional Ruddlesden–Popper (RP) perovskites has rarely been studied so far. Herein, we use first-principle calculations to investigate ferroelectric polarization and electric field control of band alignments within the RP perovskite-based heterostructure α-In2Se3/Cs2SnI2Cl2. Our calculations demonstrate that the band alignment of heterostructure can be changed from type-II to type-III by switching the ferroelectric polarization direction in the α-In2Se3 layer. Furthermore, application of an external electric field can modulate the band structure of the α-In2Se3/Cs2SnI2Cl2 heterostructure and induce the band alignment transition. These findings highlight the importance of ferroelectric polarization switching in band alignment engineering and suggest the possibility of electric field-tunable multi-band alignment in Ruddlesden–Popper perovskite-based heterostructures.

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