Stress and Defect Effects on Electron Transport Properties at SnO₂/Perovskite Interfaces: A First-Principles Insight

Abstract

The structural and electronic properties of interfaces play an important role in the stability and functionality of solar cell devices. Experiments indicate that the SnO 2 /perovskite interfaces always show superior electron transport efficiency and high structural stability even though there exists a larger lattice mismatch. Aiming at solving the puzzles, we have performed density-functional theory calculations to investigate the electronic characteristics of the SnO 2 /perovskite interfaces with various stresses and defects. The results prove that the PbI 2 /SnO 2 interfaces have better structural stability and superior characteristics for the electron transport. The tensile stress could move the conduction band minimum (CBM) of CH 3 NH 3 PbI 3 upward, while the compressive stress could move the CBM of SnO 2 downward. By taking into account the stress effect, the CBM offset is 0.07 eV at the PbI 2 /SnO 2 interface and 0.28 eV at the MAI/SnO 2 interface. Moreover, our calculations classify V I and I i at the PbI 2 /SnO 2 interface and Sn–I, I i and Sn i at the MAI/SnO 2 interface as harmful defects. The I i defects are the most easily formed harmful defects and should be avoided at both interfaces. The calculated results are in agreement with the available experimental observations. The present work provides a theoretical basis for improving the stability and photovoltaic performance of the perovskite solar cells.

Boosting the Performance of Perovskite Solar Cells through Systematic Investigation of the Annealing Effect of E-Beam Evaporated TiO2

“…Essentially, TiO 2 film consists of grain, grain boundaries, and numerous defects which play a role as barriers hindering the movement of photogenerated electrons. These crystal defects scatter the conduction of electrons and impede the flow of current leading to performance degradation of PSC [ 29 ].…”

“…Essentially, TiO 2 film consists of grain, grain boundaries, and numerous defects which play a role as barriers hindering the movement of photogenerated electrons. These crystal defects scatter the conduction of electrons and impede the flow of current leading to performance degradation of PSC [29]. Figure 5a schematically illustrates the mechanism behind the movement of carriers in EB-evaporated TiO2 film, hence affecting the performance of PSC.…”

“…Essentially, TiO2 film consists of grain, grain boundaries, and numerous defects which play a role as barriers hindering the movement of photogenerated electrons. These crystal defects scatter the conduction of electrons and impede the flow of current leading to performance degradation of PSC [29]. Elemental composition analysis of the TiO2 film was performed using Energy-Dispersive X-ray Spectroscopy (EDS) (S-4800, Hitachi, Tokyo, Japan).…”

Buried interface passivation strategies for high-performance perovskite solar cells

“…In contrast, SnO 2 is recognized as a more promising ETM 45 with high light transmittance 46 originating from the wide bandgap of ∼3.6 eV 47 and electron mobility as high as ∼240 cm 2 V −1 s −1 . 48 Additionally, it exhibits superior chemical stability even when prepared using the solution method at low temperatures.…”

Strain Effects on Flexible Perovskite Solar Cells

“…[116][117][118] As mentioned above, the strain will cause a change in B─X bond length and B─X─B bond angle, and correspondingly, the change of orbital overlap will lead to a change in band dispersion. [119,120] Pu et al [121] studied the CMB and VBM of the perovskite layer and the SnO 2 ETL boundary under the influence of different strains, and obtained two different band alignments of the SnO 2 /perovskite interface by using the Perdew-Burkes-Ernzerhof (PBE)-Heyd-Scuseria-Ernzerhof (HSE) density functional method. At the PbI 2 /SnO 2 and MAI/SnO 2 interfaces, the CBM of perovskite increases with increasing tensile strain, and the CBM of SnO 2 decreases in band structure with increasing compressive strain (Figure 6g,h).…”