Crack‐Free Monolayer Graphene Interlayer for Improving Perovskite Crystallinity and Energy Level Alignment in Efficient Inverted Perovskite Solar Cells

Abstract

Inverted planar perovskite solar cells (PSCs) have intrigued great promise in negative hysteresis, simple fabrication process, and flexible substrate implementation, in which the shared hole transport materiel is NiOx. However, the low‐temperature solution processing of the NiOx film is usually accompanied by defect formation, which deteriorates the perovskite quality and device performance. Meanwhile, the energy‐level offset between the NiOx and perovskite films is relatively large, limiting the interfacial charge transport. To suppress those setbacks, a defect‐free monolayer graphene sheet is transferred onto the NiOx film surface as a template for van der Waals epitaxial growth of perovskite films for the first time, leading to enhancing crystallinity with a large grain size of perovskite layer, 0.20 eV energy level offset drop, and accelerating charge transfer for the devices. Finally, the power conversion efficiency of 19.21% without hysteresis is achieved, exceeding 18.35% of the control device.

Comparing Charge Dynamics in Organo-Inorganic Halide Perovskite: Solid-State vs Solid-Liquid Junctions

“…Figure 2a shows the SEM cross-sectional image of FTO/PEDOT:PSS/MAPbI 3 as the working electrode, indicating a good coverage and density of the perovskite lm. Figure 2b displays the SEM cross-sectional structure diagram of the all-solid-state FTO/PEDOT:PSS/MAPbI 3 /PCBM/BCP/Ag device, with each thin lm uniformly deposited and dense, consistent with the reported p-i-n structured perovskite solar cell results [10,11].…”

Fabrication of Highly Efficient and Ambient Stable Planar MAPbI3 Perovskite Solar Cells via Defect Passivation through Crosslinking Strategy

“…Defect trap densities ( N trap ), calculated using the using the equation, [ 46 ] , where e is the elementary charge (1.6 × 10 −19 C), L is the thickness of the perovskite layer (≈500 nm from the cross‐sectional FESEM, Figure 6b), ε 0 is the permittivity of vacuum (≈8.854 × 10 −12 Fm −1 ), and ε is the relative dielectric constant of the MAPbI 3 layer (taken 28.8 [ 47 ] ). The calculated values for W & W/ o ‐TET PSCs, are 5.35 × 10 15 , and 7.77 × 10 15 cm −3 respectively and these values are similar to also similar to previously reported results.…”

Impact and Role of Epitaxial Growth in Metal Halide Perovskite Solar Cells

“…Hu et al utilized defect-free monolayer graphene sheets as a template for vdW epitaxial growth of the MAPbI 3 perovskite film on the surface of a NiO x film (Figure 9g). 141 The outcome was a significant increase in the crystallinity and grain size of the perovskite layer along with a 0.20 eV reduction in the energy level shift between NiO x and the perovskite, which accelerated charge transfer within the device. This combination of the graphene sheet and NiO x film served as an effective platform for the epitaxial growth of the perovskite layer, leading to an improved device performance (Figure 9h).…”

“…In addition to antimonene and BP, monolayer graphene (MLG) has shown great potential in optoelectronic semiconductor applications due to its exceptional electrical conductivity, extraordinary transparency, high flexibility, and stability. Hu et al utilized defect-free monolayer graphene sheets as a template for vdW epitaxial growth of the MAPbI 3 perovskite film on the surface of a NiO x film (Figure g) . The outcome was a significant increase in the crystallinity and grain size of the perovskite layer along with a 0.20 eV reduction in the energy level shift between NiO x and the perovskite, which accelerated charge transfer within the device.…”