Synergetic Effect of Chloride Doping and CH3NH3PbCl3 on CH3NH3PbI3-xClx Perovskite-Based Solar Cells

The chloride-doped CH3NH3PbI3-xClx perovskite has attracted great attention owing to clear performance enhancement by using a Cl additive and by the controversial arguments on Cl function and the mechanism behind it. Herein, a series of CH3NH3PbI3-xClx perovskites with various Cl content was prepared through a gas/solid reaction between CH3NH2 gas and CH3NH3PbI3-xClx (x= 0-1). The small amount of Cl doping in CH3NH3PbI3-xClx (x= 0.05) could lead to band gap broadening and significantly increase the perovskite grain size, and the phase-pure CH3NH3PbI2.95Cl(0.05) perovskites exhibited up to 17.44% efficiency. For Cl contents higher than 0.1 (x> 0.1), CH3NH3PbCl3 formed and coexisted with CH3NH3PbI3-xClx, and CH3NH3PbCl3 could help to improve the thermal stability of CH3NH3PbI3-xClx. However, the excessive co-existing wideband- gap CH3NH3PbCl3 perovskites would inhibit the electron transfer and lead to a deterioration of photovoltaic performance.