Synthesis, Characterization, and Photoelectric and Electrochemical Behavior of (CH 3 NH 3 ) 2 Zn 1- x Co x Br 4 Perovskites.

We report the synthesis, characterization, and photoelectric and electrochemical properties of (CH 3 NH 3 ) 2 Zn 1- x Co x Br 4 ( x = 0.0, 0.3, 0.5, 0.7, and 1.0) samples. X-ray powder and single-crystal diffraction confirm the formation of solid solution across the entire range. Additionally, as the cobalt concentration increases, the crystallinity of the samples decreases, as indicated by the powder diffraction patterns. All samples remain stable up to 560 K, beyond which they decompose into CH 3 NH 3 Br and the respective bromide. The semiconductor behavior of the compounds is confirmed through optical absorption measurements, and band gap values are determined by using the Tauc method from diffuse reflectance spectra. Raman spectroscopy reveals a slight redshift in all vibration modes with increasing cobalt content. Finally, photovoltaic measurements on solar cells constructed with (MA) 2 CoBr 4 perovskite exhibit modest performance, and electrochemical measurements indicate that the compound with the composition (MA) 2 Zn 0.3 Co 0.7 Br 4 exhibits the highest current for electrochemical water reduction during oxygen evolution.