Modulating Residual Lead Iodide via Functionalized Buried Interface for Efficient and Stable Perovskite Solar Cells

Abstract

Sufficient lead iodide (PbI 2 ) in perovskite films effectively passivates defects and enhances device performance. However, excess largegrained PbI 2 clusters tend to be randomly distributed in the perovskite layer, which mitigate the positive effect of the PbI 2 . Here, we first modulated the distribution and size of PbI 2 clusters by functionalizing the buried interface of 4,4′-diaminodiphenyl sulfone hydroiodide (DDSI 2 ). As a multifunctional modifier, DDSI 2 can optimize the energy level of tin oxide (SnO 2 ) and passivate the buried interface defects via −NH 3 + and S�O functional groups. Moreover, the hydrogen bonding and coordination between DDSI 2 and perovskite retard the crystal growth rate and alleviate the lattice stress, thereby improving the quality of the perovskite and modulating the distribution of PbI 2 . Consequently, the DDSI 2 -modified device displays a power conversion efficiency of 24.10% and a storage stability of 1800 h. We demonstrate a unique strategy for the rational control of PbI 2 for efficient and stable perovskite solar cells.

Rethinking the Role of Excess/Residual Lead Iodide in Perovskite Solar Cells

“…Recently, 4,4'‐diaminodiphenyl sulfone hydroiodide (DDSI 2 ), a multifunctional agent, has been used to effectively passivate buried interfacial defects and to modulate the distribution of PbI 2 in the study by Gao et al. [ 113 ]…”

“…[112] Such distribution improves the orientation of the perovskite grains, enhances the efficiency of the device containing residual PbI 2, and also effectively avoids its optical instability effect. Recently, 4,4'-diaminodiphenyl sulfone hydroiodide (DDSI 2 ), a multifunctional agent, has been used to effectively passivate buried interfacial defects and to modulate the distribution of PbI 2 in the study by Gao et al [113] These examples mentioned above demonstrate the positive effect of redistribution of residual PbI 2 by ionic modification techniques. According to the report of Zhu et al, residual PbI 2 is easily concentrated at the buried bottom interface.…”

NaHCO3‐induced porous PbI2 enabling efficient and stable perovskite solar cells

“…Compared with the pristine (1.56 eV), NaHCO 3 ‐treated perovskite shows a slightly reduced band gap (1.55 eV). By combining the energy levels of the perovskite layer as probed by UPS and Tauc plot with those of SnO 2 and spiro‐OMeTAD obtained from previous studies, we depicted the energy‐level diagrams with the charge extraction layers (see Table S3 for a summary of the used energy levels) 43,44 . As shown in Figure 3H, the E C (conduction band energy) of the perovskite active layer is 0.2 eV lower than that of SnO 2 , which might slightly hinder the electron extraction by the electron transport layer, and the hole extraction is also hindered due to the large E V (valence band energy) difference of 0.60 eV between perovskite and hole transport layer 45 .…”

“…By combining the energy levels of the perovskite layer as probed by UPS and Tauc plot with those of SnO 2 and spiro-OMeTAD obtained from previous studies, we depicted the energy-level diagrams with the charge extraction layers (see Table S3 for a summary of the used energy levels). 43,44 As shown in Figure 3H, the E C (conduction band energy) of the perovskite active layer is 0.2 eV lower than that of SnO 2 , which might slightly hinder the electron extraction by the electron transport layer, and the hole extraction is also hindered due to the large E V (valence band energy) difference of 0.60 eV between perovskite and hole transport layer. 45 Consequently, charge accumulation at the interfaces between the perovskite active layer and the transport layers can lead to non-radiative carrier recombination lowering the performance of PSC devices.…”

Molecular Bridge on Buried Interface for Efficient and Stable Perovskite Solar Cells

“…The compact contact and well-aligned energy levels between ETL and perovskite film allow for efficient charge extraction, suppressed charge recombination and improved long-term device stability. [5] On the contrary, loose contact and extraction barriers lead to undesired accumulation of charge carriers, which causes space charge regions and a high voltage drop at the interface, leading to enhanced charge recombination and therefore reducing the collection efficiency at a certain voltage and thus the FF, along with possible hysteresis. [6] In addition, defects located at the interface and grain boundaries (GBs) of perovskite films [7] can induce nonradiative charge recombination [8] and perovskite degradation.…”