Surface-Orientation Elimination of Vapor-Deposited PbI₂ Flakes for Efficient Perovskite Synthesis on Curved Solar Cells

Abstract

Vapor deposition of perovskite solar cells (PSCs) has attracted considerable interest for its dry processing characteristics. However, a two-step sequential vapor deposition method suffers from ineffective conversion of PbI2 to perovskite with reasons still unclear. In this report, we carefully investigated the crystallization orientation of PbI2 films deposited by physical vapor deposition via synchrotron grazing-incidence wide-angle X-ray scattering (GIWAXS) and observed an asymmetric scattering pattern with respect to the qz -axis. The observed oriented morphology and texture hinder the diffusion of MAI molecules in the PbI2 films synthesized by vapor deposition, resulting in over 15% PbI2 remaining at the buried interface after reaction with MAI vapor. As a result, the MAPbI3 synthesized in this way was also highly oriented, especially in the surface layers. Surface fumigation (SF) step was introduced to decrease the orientational anisotropy of PbI2, which successfully breaks the diffusion barriers of MAI molecules by forming a complex layer on the PbI2 surface with polar solvent vapors, like dimethyl sulfoxide or 1,3-dimethyl-2-imidazolidinone. We infer that the SF treatment changes the vapor–solid reaction mechanism from reaction–crystallization to dissolution–recrystallization, which largely promotes the conversion of PbI2 to perovskite. Defects were reduced in perovskite synthesized in this way, and a p-i-n device with 19.56% efficiency was fabricated, which is among the highest efficiencies reported for sequential-vapor-deposited PSCs. Notably, this method enables the fabrication of conformal perovskite layers on uneven substrates. An exemplary PSC showing efficiency of 8.93% was fabricated on a precurved substrate. We believe that the method is applicable to the fabrication of tandem or curved PSCs that are compatible with wearable or building/autocar-integrated photovoltaics in the future.

Passivating Perovskites in Air Via an Alternating Cation Interlayer Phase Formed by Benzylamine Vapor Fumigation

“…Perovskites obtained by vapor‐solid reaction (VSR) were fumigated with PMA gas in a petri dish for varied time, [ 4,18 ] denoted as PMA(G)‐XX, where XX denotes the fumigation time in second. We characterized the obtained films using GIWAXS.…”

“…Mapbi 3 Layers (Two-Step Vapor Deposition Method): MAPbI 3 was prepared using a VSR method, with details described in previous reports [3,4,18,21] A white light LED was used to irradiate the film during the reaction with a light intensity of 2 mW cm −2 .…”

Direct In Situ Conversion of Lead Iodide to a Highly Oriented and Crystallized Perovskite Thin Film via Sequential Deposition for 23.48% Efficient and Stable Photovoltaic Devices

“…The diffraction ring at q z = 7 nm −1 corresponds to some complexes formed by MAI, PbI 2 , and DMSO, as inferred by the following studies. 35,43,44 In the GIWAXS pattern of the PbI 2 film treated with FAFa of 0.5 mg/ mL (hereafter denoted as FAFa-0.5) and FAFa of 2 mg/mL (FAFa-2), the diffraction ring at q z = 9 nm −1 is highly concentrated along the 90°. Moreover, with the increase of the concentration of FAFa, the signal intensity of q z = 7 nm −1 also increased (Figure 1b,c).…”

Chemically Welding Silver Nanowires toward Transferable and Flexible Transparent Electrodes in Heaters and Double-Sided Perovskite Solar Cells

“…After drying in an infrared drying oven for 20 min, the ITO surface was treated with UV-ozone for 15 min. Then the electron transport layer is spin-coated on the substrate, here SnO 2 , the parameters of which are 4000 rpm for 30 s. Perovskites were synthesized by methods as previously reported. − Specifically, a mixture layer of 250 nm PbI 2 (99.985%, Xi’an p-OLED Corp) and CsBr (Xi’an p-OLED) films were coevaporated on the substrate using physical vapor deposition. In the next step, the coevaporated PbI 2 and CsBr thin films were subjected to a vapor–solid reaction to prepare perovskites.…”