Synthesis, crystal structure, absorption properties, photoelectric behavior of organic–inorganic hybrid (CH₃NH₃)₂CoCl₄

Abstract

Lead‐free and organic–inorganic hybrid (CH 3 NH 3 ) 2 CoCl 4 [(MA) 2 CoCl 4 ] single crystal and thin film are prepared. The single crystal diffraction data of (MA) 2 CoCl 4 are assigned to monoclinic, P2(1)/C space group (7.6590 × 12.6908 × 10.89350 Å, 90.0 × 96.5320 × 90.000). The absorption edge of (MA) 2 CoCl 4 reaches 730 nm. The band gap for (MA) 2 CoCl 4 is determined to be approximately 1.63 eV. To the best of our knowledge, this is the first study on (MA) 2 CoCl 4 for optoelectronic applications. A low‐cost photodetector based on (MA) 2 CoCl 4 thin film is efficient under different monochromatic light from 330 nm to 400 nm with different chopping frequencies (1.33–60 Hz). The strongest photoresponse ( I on − I off ) is under 330 nm monochromatic light with 1.33 Hz according to our optimal condition. The calculational results by density functional theory show that the narrow valence bands and conduction bands are derived from the 3p orbitals of Cl and 3d orbitals of Co.