Uniform Coverage Functional Layers Enable High‐Efficient Flexible Perovskite Solar Modules with an Outstanding Fill Factor

Abstract

Uniform and pinhole‐free functional layers are essential for high‐efficient flexible perovskite solar modules (FPSMs). However, the poor wettability of self‐assembled monolayers (SAMs) with carbazole bodies and phosphonic acid binding groups usually leads to porous large‐area perovskite films. Herein, a layer of nickel oxide nanoparticles is inserted between sputtered nickel oxide and the SAM to increase the surface energy, and thus simultaneously improving the wettability and nucleation of the perovskite during vacuum‐quenching method. Following this strategy, the best flexible perovskite solar cells with an active area of 0.09 cm2 achieve a power conversion efficiency (PCE) of 21.97% under 1 sun illumination. In addition, FPSMs with the same structure exhibit a high fill factor approach 80% and reach a champion PCE of 19.71% on 58.14 cm2 active area and a certified PCE of 18.17% on 61.26 cm2 aperture area, which is the highest recorded PCE to the best knowledge. Furthermore, the optimized interface also enhances the adhesion between hole‐transport layer and perovskite, and the encapsulated device retains 95% of its initial PCE after 1000 cycles under a 2 cm bending radius.

Chemical bath deposition of SnO2 films on PEN/ITO substrates for efficient flexible perovskite solar cells

“…Schematic illustrations of the two different methods used to obtain SnO 2 ETLs are shown in figure 4(f). The spin-coating approach often results in voids between the ITO and SnO 2 layers owing to the poor wettability of SnO 2 dispersion [13,17]. These voids cause an increase in light reflection at the interfaces, thereby diminishing the transmittance.…”

“…The PCE of the modified f-PSCs increased from 22.19% to 22.81% and retained the same stability as that of the control device. Third, the surface wettability of PEN/ITO is poorer than that of Glass/ITO and Glass/FTO, which influences the crystallization of perovskite films on it [13,17]. The presence of voids in the electron transport layers (ETLs) increases the leakage current induced by direct contact between the perovskite layers and the ITO layers [18].…”

Flexible Perovskite Solar Cells on Ultra‐Thin Stainless‐Steel with a Power‐to‐Weight Ratio over 3000 W kg−1

“…During the fabrication of FPSCs, Xu et al attached PEN substrates to glass using an OCA and the devices could be easily peeled off. [ 20 ] In this study, stainless‐steel substrates with different thicknesses were fixed using a simple homemade method, as shown in Figure S2, Supporting Information. Stainless steel with magnetic properties can be adsorbed on magnets, and a thin composite film of EVA‐PET‐EVA was inserted between the stainless steel and the magnet to avoid displacement during spin‐coating.…”

“…[ 18,19 ] Xu et al addressed this problem by introducing a nano wetting agent to increase the roughness of substrates. [ 20 ] On the other hand, a smooth surface decreases the number of nucleation sites during the heterogeneous nucleation process of perovskite and leads to the non‐dense growth of perovskite crystals. [ 32 ] Both of these problems may lead to the formation of pinholes during the fabrication of perovskites.…”

“…[ 18,19 ] Xu et al improved the wettability of the substrate by introducing NP‐NiO x as a wetting agent, such that the perovskite film was uniformly deposited, thereby reducing the generation of holes. [ 20 ] It is difficult to achieve flat and fixed ultra‐thin stainless‐steel substrates. The commonly used optically clear adhesive (OCA) flattening method can easily cause damage to ultra‐thin stainless‐steel devices when removed.…”