Nanoarchitectonics of lead-free 2D cobalt-based diammonium hybrid for perovskites solar cell applications

This study presents the fabrication of new, non-toxic perovskite solar cells using 2D cobalt-based perovskite materials. Three cobalt-based Organic–inorganic 2D hybrid perovskite (HOIP) materials were synthesized, and their photovoltaic properties were evaluated: [NH3(CH2)nNH3]CoCl4 (n = 4, 9) and [NH3(CH2)7NH3]CoBr2Cl2. These materials encompassed varying organic chain lengths (short, medium, and long) as well as chloride and mixed chloride/bromide anions. The molecular structure was examined to establish correlations with the structural and optical properties. The synthesized compounds exhibited visible light absorption, with varying bandgap energy from 1.7 eV to 2.7 eV. To test the application of Co-based perovskites, two distinct solar cell architectures were employed. The first architecture, denoted as Architecture 1, consisted of the following layers: Glass/FTO/c-TiO2/m-TiO2/ZrO2/2D Co-based HOIP/C-electrode. The second architecture, referred to as Architecture 2, utilized a planar heterojunction structure deposited with different transport layers for electrons and holes. Specifically, it comprised the layers: Glass/ITO/SnO2/2D Co-based HOIP/Spiro-OMeTAD/Au. Among these architectures, Architecture 2 exhibited notable performance. It achieved a maximal open circuit voltage (Voc) of 0.93 V, and current density (Jsc) of 0.24 mA/cm2, with efficiency of 0.47%, and a fill factor (FF) of 78%. These findings demonstrate the effectiveness of adjusting the perovskite material composition and controlling the deposition conditions in raising solar cell efficiency.