Enhanced efficiency and stability of perovskite solar cells by partial replacement of CH3NH3+ with inorganic Cs+ in CH3NH3PbI3 perovskite absorber layer

u In this work, we have investigated the (MA)(1-x)CsxPbI3(MA = CH3NH3; x = 0-1) perovskite based solar cells. The x-ray diffraction analysis revealed that crystal structure of the material has been transformed from tetragonal to orthorhombic phase with Cs doping. The optical spectra are blue shifted with Cs doping, suggesting the increase in the band gap and this effect is more prominent in higher Cs doping. From x-ray photoemission spectroscopy analysis, binding energy difference between Pb and I doublets is observed to be fixed. The oxygen and carbon peaks responsible for decomposition of MAPbI(3) decreases in intensity in partial doped sample, showing the stability of the material by introducing oxidation stable Cs. The power conversion efficiency (PCE) was investigated and the best performing device with PCE of 15.37% was achieved with 30% Cs doping, with open circuit voltage of 1.08 V, current density of 19.70 mA/cm(2), and fill factor of 0.72.