Stable perovskite solar cells with 22% efficiency enabled by inhibiting migration/loss of iodide ions

Iodide ions (I^- and I₃^-) in perovskites tend to migrate resulting in phase segregation and degradation of perovskite films and devices under illumination or operation conditions. In order to overcome this intrinsic difficulty, passivation and additive strategies have been developed in many studies. In this work, we introduced polyetheramine (PEA) into perovskite films to inhibit the migration and loss of iodides and suppress defects related to these migrated ions. The perovskite films with PEA barely suffered iodide loss even under long-term ultraviolet (UV) illumination and possessed a lower trap density than that of the pristine films before and after aging under UV illumination. Density functional theory (DFT) calculations revealed that PEA can form strong interactions with iodides and Pb²⁺ in perovskites via PbO and H-I bonds, and the iodide ions (I^- and I₃^-) could be locked firmly by PEA, preventing them from migration or loss. Using this method, the efficiency of perovskite solar cells (PSCs) can be improved from 19.71% (without PEA) to 22.02% (with PEA). After 200 h of maximum power point (MPP) tracking, the efficiency of PSCs with PEA remained 89% of its initial value and that of PSCs without PEA fully degraded.