Heterocyclic amino acid molecule as a multifunctional interfacial bridge for improving the efficiency and stability of quadruple cation perovskite solar cells

Regulating the charge extraction ability of electron transport materials and constructing a chemically linked interface are imperative to enhance the power conversion efficiencies (PCEs) and improve the device stability of perovskite solar cells (PSCs). Herein, a heterocyclic amino acid molecule of 3-amino-4-pyrazolecarboxylic acid (APA) is incorporated into the SnO2/perovskite interface to improve the device performance via a multifunctional interfacial bridge. The carboxylic group and pyrazole N in APA significantly improve the optoelectronic properties of SnO2, such as carrier mobility, conductivity, energy levels and trap-state. Meanwhile, the pre-buried APA effectively passivates the buried perovskite interface, enhances the crystallinity of perovsite film and boosts the carrier extraction efficiency through chemically linking SnO2 and perovskite. As a result, the champion device delivers an impressive PCE of 24.71 % along with a fill factor of 83.56 %, which is one of the highest efficiencies for RbCsFAMA quadruple cation PSCs. Moreover, over 83 % and 80 % of their initial efficiencies are retained after 2400 h of storage and 500 h of continuous maximum output power point tracking under 1 sun illumination (white light LED array) for the unencapsulated devices, respectively. This work offers a facile approach to construct a robust interfacial bridge for efficient and stable PSCs.