Recent Progress of Surface Passivation Molecules for Perovskite Solar Cell Applications

Abstract

Due to the solution processable nature, the prepared perovskite films are polycrystalline with considerable number of defects. These defects, especially defects at interface accelerate the carrier recombination and reduce the carrier collection. Besides, the surface defects also affect the long-term stability of the perovskite solar cells (PVSCs). To solve this problem, surface passivation molecules are introduced at selective interface (the interface between perovskite and carrier selective layer). This review summarizes recent progress of small molecules used in PVSCs. Firstly, different types of defect states in perovskite films are introduced and their effects on device performance are discussed. Subsequently, surface passivation molecules are divided into four categories, and the interaction between the functional groups of the surface passivation molecules and selective defect states in perovskite films are highlighted. Finally, we look into the prospects and challenges in design noble small molecules for PVSCs applications.

Self‐assembled monolayers for perovskite solar cells

“…; X generally refers to monovalent halogen anions such as I − , Cl − , and Br − . The B‐site cation forms a [BX 6 ] 4− octahedral coordination structure with six X anions, while the A‐site cation exhibits a 12‐coordinated structure, located within the interstitial voids formed by cube octahedra 1 . The unique ionic properties and rapid crystallization process 2 of perovskite (PVK) lead to the generation of a large number of lattice defects, especially high defect density surface states 3 …”

“…When MOs directly contact with PVK, the presence of defect‐rich surface states leads to a considerable recombination of photogenerated carriers 5 . Additionally, due to the difference in Fermi levels and the presence of deep trap states, a potential barrier is formed at the interface, known as the Schottky barrier 1,5 . Moreover, the chemical reactions between MOs and PVK, including acid–base neutralization and oxidation–reduction reactions, accelerate the degradation of the interface layer 6 .…”

Reducing the Surface Reactivity of Alkyl Ammonium Passivation Molecules Enables Highly Efficient Perovskite Solar Cells

“…Surface passivation has been proven to be an effective strategy to reduce non-radiative recombination caused by defects. [22,23] Recently, many materials have been developed for surface passivation, such as Lewis acids, Lewis bases, 2D perovskites, and organic ammonium salts. [10,[24][25][26][27][28][29][30][31][32][33][34][35] Lewis acid or Lewis base can only passivate one type of charged defect (positively or negatively charged) on the perovskite surface depending on their electron accepting or donating property.…”