Synergistic improvements in stability and performance of lead iodide perovskite solar cells incorporating salt additives

Abstract

The main issues in planar perovskite solar cells are the coverage and crystallinity of the perovskite film on the PEDOT:PSS layer. To enhance these features, we introduced alkali metal halides (salts) as additives into the perovskite precursor solution used in a two-step preparation method. These alkali metal halides chelate with Pb²⁺ ions and enhance the crystal growth of PbI₂ films, resulting in nanostructured morphologies. The nanostructured PbI₂ films promote homogeneous nucleation and larger crystallite sizes, thereby enhancing the morphology and crystallinity of the perovskite films. The alkali metal halides recrystallize the small grains and passivate the grain boundaries and interface states, allowing effective charge generation and dissociation in perovskite films. Photoluminescence measurements indicated that perovskite films prepared with salt additives featured fewer charge traps and defects. The power conversion efficiency of the device incorporating a small amount of a salt additive increased by approximately 33%—from 11.4 to 15.08%. This device was more stable than a corresponding device prepared without the additive, with only 16.5% degradation occurring over a period of 50 days.