The Role of SnO2 Processing on Ionic Distribution in Double-Cation-Double Halide Perovskites

Decreased Hysteresis Benefited from Enhanced Lattice Oxygen and Promoted Band Alignment with Electron Transport Layer Modification in Perovskite Solar Cells

SnO2 electron transport layer (ETL) morphology plays a vital role in carrier transportation and the properties of perovskite solar cells (PSCs). However, the uneven and pore surface would inevitably lead to high interface defects, high hysteresis, and poor performance. In this work, we use a molecular modifier 4-guanidinobenzoic acid methanesulfonate (GAMSA) to build a molecular bridge on the buried interface of SnO2/perovskite. XPS results demonstrate that the ratio of lattice oxygen (OL)/adsorbed oxygen (OV) increased from 1.35 to 2.34 after GAMSA modification, thus, Sn4+ and O vacancy defects in SnO2 were effectively reduced. Meanwhile, the conduction band minimum of the ETL enhanced from -4.33 eV to -4.07 eV, which obviously facilitated the electron transport. As a result, the optimal device exhibits an enhanced efficiency of 22.42%, which is much higher than that of the control one of 20.13%, with a greatly decreased hysteresis index from 14.35% to 3.27%. Notably, the optimized target device demonstrated excellent long-term stability, maintaining an initial efficiency of 87% after 2000 h storage in a N2 atmosphere in the dark at room temperature. This work paves a new method of ETL modification to improve lattice oxygen of SnO2 and restrain hysteresis for the enhanced performance of PSCs.

Simultaneous Interfacial Defect Passivation and Bottom-Up Excess PbI2 Management via Rubidium Chloride in Highly Efficient Perovskite Solar Cells with Suppressed Hysteresis

In halide perovskite solar cells (PSCs), moderate lead iodide (PbI2) can enhance device efficiency by providing some passivation effects, but extremely active PbI2 leads to the current density-voltage hysteresis effect and device instability. In addition, defects distributed on the buried interface of tin oxide (SnO2)/perovskite will lead to the photogenerated carrier recombination. Here, rubidium chloride (RbCl) is introduced at the buried SnO2/perovskite interface, which not only acts as an interfacial passivator to interact with the uncoordinated tin ions (Sn4+) and fill the oxygen vacancy on the SnO2 surface but also converts PbI2 into an inactive (PbI2)2RbCl compound to stabilize the perovskite phase via a bottom-up evolution effect. These synergistic effects deliver a champion PCE of 22.13% with suppressed hysteresis for the W RbCl PSCs, in combination with enhanced environmental and thermal stability. This work demonstrates that the interfacial defect passivation and bottom-up excess PbI2 management using RbCl modifiers are promising strategies to address the outstanding challenges associated with PSCs.