Synergistic lattice regulation of additive and interface engineering to realize high efficiency CsPbI₂Br perovskite solar cell

The CsPbI2Br material has gained recognition as an exceptional candidate for both single- and multi- junction solar cells due to its remarkable thermal and light stability, along with its suitable band gap. However, despite these inherent advantages, CsPbI2Br perovskite solar cells (PSCs) still encounter significant energy losses, which impede the further enhancement of their efficiency. Although various approaches involving additives and interface engineering techniques improved device performance, the influence of these methods on the perovskite lattice is frequently overlooked. Herein, synergistic lattice regulation through the combination of potassium acetate (KAc) as electron interface layer and methylammonium chloride (MACl) as perovskite additive, was proposed. The MACl dopant effectively increases the crystallinity and grain size of CsPbI2Br film by retarding the crystallization rate of perovskite, resulting in the enhancement in short-circuit current density (J(sc)) of PSCs. Unfortunately, unlike the behavior observed in inorganic-organic perovskites, the introduction of Cl- from MACl into the interstitial positions leads to lattice expansion in CsPbI2Br, resulting in reduced open-circuit voltage (V-oc) and fill factor (FF). However, the incorporation of K+ replacing Cs+ effectively mitigates lattice distortion phenomena. Consequently, the CsPbI2Br PSCs, benefiting from the complementary effects of the MACl additive and KAc interfacial layer, exhibit an outstanding champion power conversion efficiency of 17.11 %. This research offers profound insights into the impact of ions introduced through additive and interface engineering on perovskite lattice stress.