Revealing Steric‐Hindrance‐Dependent Buried Interface Defect Passivation Mechanism in Efficient and Stable Perovskite Solar Cells with Mitigated Tensile Stress

Abstract

Interface engineering is one feasible and effective approach to minimize the interfacial nonradiative recombination stemming from interfacial defects, interfacial residual stress, and interfacial energy level mismatch. Herein, a novel and effective steric-hindrance-dependent buried interface defect passivation and stress release strategy is reported, which is implemented by adopting a series of adamantane derivative molecules functionalized with CO (i.e., 2-adamantanone (AD), 1-adamantane carboxylic acid (ADCA), and 1-adamantaneacetic acid (ADAA)) to modify SnO 2 /perovskite interface. All modifiers play a role in passivating interfacial defects, mitigating interfacial strain, and enhancing device performance. The steric hindrance of chemical interaction between CO in these molecules and perovskites as well as SnO 2 is determined by the distance between CO and bulky adamantane ring, which gradually decreases from AD, ADCA, and ADAA. The experimental and theoretical evidences together confirmed steric-hindrance-dependent defect passivation effect and interfacial chemical interaction strength. The interfacial chemical interaction strength, defect passivation effect, stress release effect and thus device performance are negatively correlated with steric hindrance. Consequently, the ADAA-modified device achieves a seductive efficiency up to 23.18%. The unencapsulated devices with ADAA maintain 81% of its initial efficiency after aging at 60 °C for 1000 h.

Regulating the Interplay at the Buried Interface for Efficient and Stable Carbon-Based CsPbI2Br Perovskite Solar Cells

“…From the FTIR results in Figures 1f and S9, we observed that the stretching vibration of C�O from PbI 2 /EAD shifted toward a lower wavenumber as compared to the EAD molecule, indicating a strong interaction between carbonyl groups in EAD and Pb 2+ . 35,36 Meanwhile, the N−H bonding shifted to a lower wavenumber after mixing PbI 2 and EAD (Figure 1g), demonstrating the formation of N−H•••I hydrogen bonding, which could passivate halide ion defects. 21,37 According to previous reports, ammonium cations may also interact with the Pb−I framework to modulate the growth of perovskite films.…”

[PbX6]4−modulation and organic spacer construction for stable perovskite solar cells

“…Regarding the buried interface stress and defect, Chen et al adopted adamantane-derivative molecules with CO functional groups to tune the steric hindrance of chemical interaction at the SnO 2 /perovskite interface, which effectively passivated the interfacial defect and mitigated the interfacial strain. 189 In addition, the ionic motion induced by an electric field resulted in increased interfacial lattice strain and even collapse of the structure, which was directly related to the stability. 190 Adopting a fullerene derivative to release the interface strain could effectively inhibit the formation of interface defects and enhance the structure stability (Fig.…”

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

“…41,42 It should be noted that residual tensile stress is an factor affecting the stability of perovskite films. 27 In contrast, the GIXRD peaks of the DDSI 2 perovskite film (Figure S17b) show a trend toward higher angles by a change in φ and the corresponding slope becomes positive (Figure S17c). This result implies that DDSI 2 modification can effectively alleviate the residual stress, improving the longterm stability of PSCs.…”

“…Furthermore, the 2θ sin 2 φ method was employed to examine the surface residual stress state of the perovskite films. , For pristine perovskite films (Figure S17a), the characteristic diffraction peaks show a shift to lower angles with φ from 10 to 60°, indicating that the interplanar spacing gradually increases according to Bragg’s law . The negative slope of the linear fit of 2θ sin 2 φ shows the tensile stress of the pristine perovskite (Figure S17c), consistent with previous reports. , It should be noted that residual tensile stress is an factor affecting the stability of perovskite films . In contrast, the GIXRD peaks of the DDSI 2 perovskite film (Figure S17b) show a trend toward higher angles by a change in φ and the corresponding slope becomes positive (Figure S17c).…”

“…There have been few systematic studies on the distribution of PbI 2 on the surface of perovskite grains. Moreover, previous literature on the morphology and distribution of PbI 2 was mainly focused on perovskite precursor solution additives and postprocessing of perovskite films. − It is worth noting that the buried interface is also one of the primary factors affecting the quality of perovskite films and residual PbI 2 , but its importance is often overlooked. − …”