Improvement of CH₃NH₃PbI₃ Formation for Efficient and Better Reproducible Mesoscopic Perovskite Solar Cells

Abstract

High-performance perovskite solar cells (PSCs) are obtained through optimization of the formation of CH3NH3PbI3 nanocrystals on mesoporous TiO2 film, using a two-step sequential deposition process by first spin-coating a PbI2 film and then submerging it into CH3NH3I solution for perovskite conversion (PbI2 + CH3NH3I → CH3NH3PbI3). It is found that the PbI2 morphology from different film formation process (thermal drying, solvent extraction, and as-deposited) has a profound effect on the CH3NH3PbI3 active layer formation and its nanocrystalline composition. The residual PbI2 in the active layer contributes to substantial photocurrent losses, thus resulting in low and inconsistent PSC performances. The PbI2 film dried by solvent extraction shows enhanced CH3NH3PbI3 conversion as the loosely packed disk-like PbI2 crystals allow better CH3NH3I penetration and reaction in comparison to the multicrystal aggregates that are commonly obtained in the thermally dried PbI2 film. The as-deposited PbI2 wet film, without any further drying, exhibits complete conversion to CH3NH3PbI3 in MAI solution. The resulting PSCs reveal high power conversion efficiency of 15.60% with a batch-to-batch consistency of 14.60 ± 0.55%, whereas a lower efficiency of 13.80% with a poorer consistency of 11.20 ± 3.10% are obtained from the PSCs using thermally dried PbI2 films.

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

“…An additional aspect of their method is the spin-coating of PbI 2 at an elevated temperature, which controls the evaporation rate of the solvent (DMF) and leads to an optimized film porosity to accommodate the volume expansion during the transformation to the perovskite phase. [37] Jiang et al [95] and Ko et al [96] studied the effect of PbI 2 film morphology on device performance and reproducibility and found that it strongly affects these parameters. In order to overcome large deviations in film morphology and composition, these authors proposed an alternative protocol where the MAI solution with high ion concentration was spin-coated onto the PbI 2 film.…”

Dynamic electrical behavior of halide perovskite based solar cells

“…The CH 3 NH 3 PbI 3−x Cl x based solar cells were fabricated using two-step deposition method [38,39,40]: the PbI 2 + PbCl 2 films were spin-coated on the FTO/TiO 2 /mp-TiO 2 structures and then dried for 15 minutes at 110 • C. In order to obtain the CH 3 NH 3 PbI 3−x Cl x hybrid compound, the FTO/TiO 2 /mp-TiO 2 /PbI 2 +PbCl 2 structure was dipped in a solution of CH 3 NH 3 I and anhydrous 2-propanol (10mg −1 ml −1 ) and then rinsed in 2-propanol. The hole transporter material -2,2',7,7'-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'spirobifluorene (spiro-OMeTAD) dissolved in chlorobenzene and tert-butylpyridine, litiumbis (trifluoromethylsulphonyl) imide in acetonitrile -was deposited by spin-coating in N 2 enriched atmosphere, at room temperature (∼24 • C) and humidity less than 10%.…”

High‐Purity Hybrid Organolead Halide Perovskite Nanoparticles Obtained by Pulsed‐Laser Irradiation in Liquid

“…[3,29] The wet-chemistry synthetic procedures reported to date are based on ac ommon strategy: the metal-halides ource and alkylammonium halides are dissolved in a" good" highly polar solvent and then injected into a" poor" nonpolars olvent that contains surfactants, such as oleic acid and oleylamine. [29,39,40] However,t he decomposition of HyP-NPs during purification steps has often been observed. [2,29,35] An excesso fs urfactants and alkylammonium halide is typically required to increaset he solubility of the intermediate metal-halide species.…”

“…[37] In fact, the perovskite layer not only functions as the optically active medium, but also as at ransporter of electrons and/orh oles, [38] which is directly related to the absence of insulatingl ayers at nanocrystal interfaces. [29,39,40] However,t he decomposition of HyP-NPs during purification steps has often been observed. [2] Here we used pulsed-laser irradiation in al iquid environment (PLIL) to obtain ac olloid of HyP-NPs in CHCl 3 in one step withouta ny additive,s urfactant, or excess chemical agent.…”