Optimizing Lignosulfonic Acid-Grafted Polyaniline as a Hole-Transport Layer for Inverted CH₃NH₃PbI₃Perovskite Solar Cells

Abstract

A conducting polymer of lignosulfonic acid-grafted, polyaniline-doped camphorsulfonic acid (LS-PANI-CSA), created via a low-temperature solution process, has been explored as an efficient hole-transport layer (HTL) for inverted single cation–anion CH3NH3PbI3 perovskite solar cells. The performance of the solar cell was optimized in this study by tuning the morphology and work function of LS-PANI-CSA films using dimethylsulfoxide (DMSO) as a solvent in treatment. Results showed that DMSO washing enhanced the electronic properties of the LS-PANI-CSA film and increased its hydrophobicity, which is very important for perovskite growth. The perovskite active layer deposited onto the DMSO-treated LS-PANI-CSA layer had higher crystallinity with large grain sizes (>5 μm), more uniform and complete surface coverage, and very low pinhole density and PbI2 residues compared to untreated LS-PANI-CSA. These enhancements result in higher device performance and stability. Using DMSO-treated LS-PANI-CSA as an HTL at 15 nm of thickness, a maximum 10.8% power conversion efficiency was obtained in ITO/LS-PANI-CSA/MAPbI3/PCBM/BCP/Ag inverted-device configurations. This was a significant improvement compared to 5.18% for devices based on untreated LS-PANI-CSA and a slight improvement over PEDOT:PSS-based devices with 9.48%. Furthermore, the perovskite based on treated LS-PANI-CSA showed the higher stability compared to both untreated LS-PANI-CSA and PEDOT:PSS HTL-based devices.

Improved efficiency of inverted planar perovskite solar cells with an ultrahigh work function doped polymer as an alternative hole transport layer

“…The absolute surface WF can be estimated after the tip is calibrated with a highly oriented pyrolytic graphite (HOPG) sample. 49 As labeled in Fig. 3f, the average WF increased as the content of PFI increased in the S-P3MEET polymer.…”

“…This finding is due to the lower wettability of the mixedcation lead mixed-halide perovskite precursor solution on the fluorinated S-P3MEET substrate. 49,50 Increasing the PFI doping level in the S-P3MEET polymer more led to further reduction in grain size of the perovskite films due to the acidity of the PFI. 51,52 It has been reported that depositing perovskite onto a neutral HTL enhances the nucleation and crystallization of a perovskite active layer, with more uniform grain sizes, than depositing it onto acidic and/or basic HTL surfaces.…”

“…The lower grain size and lower grain boundary passivation perovskite films on the PEDOT:PSS surface could be attributed to the wettability and control over the Ostwald ripening process. 48,49 The grain size statistics (Fig. 2f-j) showed that the average grain sizes of the perovskite films were 1.05 mm, 0.88 mm, 0.62 mm, 0.51 mm, and 0.796 mm when perovskite was deposited onto the pristine S-P3MEET, S-P3MEET-5% wt PFI, S-P3MEET-10% wt PFI, S-P3MEET-15% wt PFI, and PEDOT:PSS, respectively.…”

Simple Solution‐Processed Approach for Nanoscale Coverage of Perovskite on Textured Silicon Surface Enabling Highly Efficient Perovskite/Si Tandem Solar Cells

“…Meanwhile, the optical bandgap of the perovskite + starch films from the Tauc plot is shown in Figure 4b. [ 34 ]…”

“…Meanwhile, the optical bandgap of the perovskite þ starch films from the Tauc plot is shown in Figure 4b. [34] The steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) attenuation spectra of these perovskite þ starch films are shown in Figure 4c,d, respectively. Particularly, a slight redshift of the absorption and PL were observed, which could be attributed to the different morphology of the perovskite crystal of each film sample.…”