Morphology and Crystallinity Amelioration of MAPbI₃ Perovskite in Virtue of PbI₂ Thermal Absorption Drifted Performance Enhancement in Planer n–i–p Solar Cells

Abstract

Sequential deposition route is widely investigated in fabricating perovskite thin films for state‐of‐the‐art perovskite photovoltaics. However, concerns such as lower morphological control, phase purity, and remnant unreacted salts methylammonium iodide (MAI and PbI2) are raised, which can significantly deteriorate optoelectronic properties, hence the operational durability of the devices. Herein, a facile two‐step method to prepare high‐quality perovskite thin films with reproducibility is reported, as‐spun PbI2 is annealed at varying thermal input under controlled rate, and a trend in converted perovskite film properties is noted. Specifically, PbI2 thin film annealed at 200 °CC results in 20x intensified crystallinity with pinholes free and a subsequent reduction in the crystal microstrain. In addition, it provides higher surface roughness to load more MAI [in iso‐propyl alcohol (IPA)]; therefore, a higher perovskite conversion is achieved. This method enables a significant efficiency enhancement in the treated sample (Pero@PbI2‐200 °C) as compared with controlled film; it retains around 90% initial efficiency after 384 h of ambient exposure. Furthermore, a facile intermediate solvent treatment method to gain the complete conversion of PbI2 into perovskite is also reported. This study highlights the importance of morphological control in governing optoelectronic properties, hence the efficiency and stability of perovskite solar cells.

Flexible and Filter‐Free Color‐Imaging Sensors with Multicomponent Perovskites Deposited Using Enhanced Vapor Technology

“…Consequently, by conserving the morphology of the PbBr 2 films, the subsequent perovskite films on the functionalized substrates exhibit fewer defects and a larger grain size than the bare substrate. [32] Second, the PbBr 2 crystals start to expand as they are converted to a perovskite via the migration of CsBr from the grain boundaries and, owing to lateral confinement, the grains are forced to grow vertically, resulting in small grains and high surface roughness. However, forming SAMs with alkyls can mitigate interface strain, contributing to the formation of large grains.…”

Poly(vinylidene fluoride‐co‐hexafluoropropylene) additive in perovskite for stable performance of carbon‐based perovskite solar cells

“…This arises due to the PVDF‐HFP additive, which can be chemical bridging to the MA cation and improving the crystallization of perovskites with high‐quality films with larger crystal grains. The crystallite size of the MAPbI 3 and MAPbI 3 with PVDF‐HFP additive films was calculated by the Scherrer formula 31 . The crystallite size for the MAPbI 3 film was 60 nm and the PVDF‐HFP with 1, 3, 5, and 7 wt % are 75, 84, 92, and 82 nm, respectively.…”

“…The crystallite size of the MAPbI 3 and MAPbI 3 with PVDF-HFP additive films was calculated by the Scherrer formula. 31 The crystallite size for the MAPbI 3 film was 60 nm and the PVDF-HFP with 1, 3, 5, and 7 wt % are 75, 84, 92, and 82 nm, respectively. Moreover, the improved crystallization of the (110) plane in perovskite films with polymer additive-based CPSC device shows a high opencircuit voltage (V oc ), which can lead to high photovoltaic performance.…”

Molecular design for perovskite solar cells

“…Many efforts have been devoted to modifying the precursor solution, additives, and solvents, such as on those for FAPbI 3 preparation, 56‐58 additive MACl, 59‐62 ionic liquid, 63‐65 and MAPbBr 3 quantum dots 66‐68 . For example, the AX and BX 2 precursors in the precursor solution are essentially in the molecular form at the starting point, and non‐stoichiometric precursors are viable to generate improved perovskite film quality; the unreacted PbI 2 is suggested to improve the perovskite film crystallinity 69‐71 and facilitate the electron transfer to the neighboring TiO 2 layer. Compositionally engineering the methylammonium precursor is common, 72,73 and switching to the chloride‐based methylammonium precursor solution can help the crystallization of the triple A‐cation perovskite film 74,75 …”