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Peer-reviewedCC BY 4.0Polymers

Engineering Larger Grains in MAPbI3 Solar Cells via Covalent Organic Framework (COF)-Assisted Crystallization: High-Performance Devices with Superior Stability Under Prolonged Illumination

  • E. M. Mkawi1,2
  • Saif M. H. Qaid2
  • Abdullah S. Aldwayyan2
  • Prastika Krisma Jiwanti3
  • Chia Ching Kee4
  • Sok Kuan Wong5
  • E. Bekyarova6
  • Yew Hoong Wong1
6 affiliations
  1. 1Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur 50603, Malaysia
  2. 2Physics and Astronomy Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
  3. 3Nanotechnology Engineering, Faculty of Advanced Technology and Multidiscipline, Universitas Airlangga, Surabaya 60115, Indonesia
  4. 4School of Engineering, Faculty of Engineering and Technology, Sunway University, Bandar Sunway, Petaling Jaya 47500, Selangor, Malaysia
  5. 5Department of Pharmacology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Bandar Tun Razak, Cheras, Kuala Lumpur 56000, Malaysia
  6. 6Department of Chemistry, University of California at Riverside, Riverside, CA 92521, USA
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Abstract

Methylammonium lead iodide (MAPbI3) is a benchmark absorber for low-cost, high-efficiency perovskite solar cells (PSCs), but its practical deployment is constrained by small grain sizes, high defect densities, and moisture-sensitive surfaces that limit both efficiency and stability. Here, we demonstrate that covalent organic frameworks (COFs) built from commercially available building blocks provide a powerful, multifunctional route to overcome these limitations by simultaneously regulating crystallization, passivating defects, and tuning surface properties in MAPbI3 thin films. Three hydrazone-linked and β-ketoenamine frameworks, denoted DMTH-COF, Boc-PDA-COF and Tp-COF, were prepared by condensing 2,5-dimethoxyterephthalohydrazide (DMTH), Boc-PDA-phenylenediamine (Boc-PDA), and 1,3,5-triformylphloroglucinol (Tp), respectively, and were incorporated at low loading into the MAPbI3 precursor solution. X-ray diffraction and FE-SEM reveal that all three additives preserve the tetragonal perovskite phase while enlarging the grain size from a few hundred nanometers in pristine films to about 1 μm for DMTH-modified layers, accompanied by narrowed diffraction peaks and reduced microstrain. Raman and FTIR spectroscopy show COF-induced modifications of Pb–I and CH3NH3+ vibrational modes, indicating specific coordination and hydrogen-bonding interactions that stabilize the lattice and reduce trap density. UV-Vis spectra confirm strong visible-light absorption at an unchanged optical bandgap of 1.56 eV across all films, while steady-state PL and EQE measurements evidence enhanced radiative efficiency and improved photon-to-current conversion, particularly at longer wavelengths. X-ray photoelectron spectroscopy confirms that the framework is retained within the film after annealing, the modified absorber showing a N 1s component at 399.7 eV that is absent from the pristine reference, while the Pb 4f and I 3d core levels shift in parallel with their spin–orbit splittings preserved and no metallic lead detected. These material-level improvements translate into substantial device gains in n-i-p PSCs (FTO/c-TiO2/m-TiO2/COF:MAPbI3/Spiro-OMeTAD/Au). Relative to pristine MAPbI3 cells (PCE ≈ 14.7%), COF-modified devices exhibit higher Voc, Jsc, and FF, with DMTH-COF-modified cells achieving Voc = 1.183 V, Jsc = 22.98 mA cm−2, FF = 76.46%, and PCE = 20.78%, alongside reduced series resistance, increased shunt resistance, and improved device-to-device reproducibility. Water-contact-angle and EDX analyses confirm that COF addition increases surface hydrophobicity and preserves near-ideal Pb:I stoichiometry, supporting enhanced environmental stability. This study introduces bulk COF doping as a simple, scalable strategy to engineer MAPbI3 microstructure, energetics, and surface chemistry in a single processing step, and identifies DMTH-COF as the most effective of the three frameworks. More broadly, it positions COF–perovskite hybrids as a tunable platform for high-efficiency, durable perovskite optoelectronics.

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Cite

BibTeXRIS
BibTeX
@article{mkawi2026engineering,
  title = {{Engineering Larger Grains in MAPbI3 Solar Cells via Covalent Organic Framework (COF)-Assisted Crystallization: High-Performance Devices with Superior Stability Under Prolonged Illumination}},
  author = {E. M. Mkawi and Saif M. H. Qaid and Abdullah S. Aldwayyan and Prastika Krisma Jiwanti and Chia Ching Kee and Sok Kuan Wong and E. Bekyarova and Yew Hoong Wong},
  journal = {Polymers},
  year = {2026},
  month = oct,
  doi = {10.3390/polym18202535},
  url = {https://www.mdpi.com/2073-4360/18/20/2535},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Engineering Larger Grains in MAPbI3 Solar Cells via Covalent Organic Framework (COF)-Assisted Crystallization: High-Performance Devices with Superior Stability Under Prolonged Illumination
AU  - E. M. Mkawi
AU  - Saif M. H. Qaid
AU  - Abdullah S. Aldwayyan
AU  - Prastika Krisma Jiwanti
AU  - Chia Ching Kee
AU  - Sok Kuan Wong
AU  - E. Bekyarova
AU  - Yew Hoong Wong
PY  - 2026
DA  - 2026/10/01
JO  - Polymers
DO  - 10.3390/polym18202535
UR  - https://www.mdpi.com/2073-4360/18/20/2535
AB  - Methylammonium lead iodide (MAPbI3) is a benchmark absorber for low-cost, high-efficiency perovskite solar cells (PSCs), but its practical deployment is constrained by small grain sizes, high defect densities, and moisture-sensitive surfaces that limit both efficiency and stability. Here, we demonstrate that covalent organic frameworks (COFs) built from commercially available building blocks provide a powerful, multifunctional route to overcome these limitations by simultaneously regulating crystallization, passivating defects, and tuning surface properties in MAPbI3 thin films. Three hydrazone-linked and β-ketoenamine frameworks, denoted DMTH-COF, Boc-PDA-COF and Tp-COF, were prepared by condensing 2,5-dimethoxyterephthalohydrazide (DMTH), Boc-PDA-phenylenediamine (Boc-PDA), and 1,3,5-triformylphloroglucinol (Tp), respectively, and were incorporated at low loading into the MAPbI3 precursor solution. X-ray diffraction and FE-SEM reveal that all three additives preserve the tetragonal perovskite phase while enlarging the grain size from a few hundred nanometers in pristine films to about 1 μm for DMTH-modified layers, accompanied by narrowed diffraction peaks and reduced microstrain. Raman and FTIR spectroscopy show COF-induced modifications of Pb–I and CH3NH3+ vibrational modes, indicating specific coordination and hydrogen-bonding interactions that stabilize the lattice and reduce trap density. UV-Vis spectra confirm strong visible-light absorption at an unchanged optical bandgap of 1.56 eV across all films, while steady-state PL and EQE measurements evidence enhanced radiative efficiency and improved photon-to-current conversion, particularly at longer wavelengths. X-ray photoelectron spectroscopy confirms that the framework is retained within the film after annealing, the modified absorber showing a N 1s component at 399.7 eV that is absent from the pristine reference, while the Pb 4f and I 3d core levels shift in parallel with their spin–orbit splittings preserved and no metallic lead detected. These material-level improvements translate into substantial device gains in n-i-p PSCs (FTO/c-TiO2/m-TiO2/COF:MAPbI3/Spiro-OMeTAD/Au). Relative to pristine MAPbI3 cells (PCE ≈ 14.7%), COF-modified devices exhibit higher Voc, Jsc, and FF, with DMTH-COF-modified cells achieving Voc = 1.183 V, Jsc = 22.98 mA cm−2, FF = 76.46%, and PCE = 20.78%, alongside reduced series resistance, increased shunt resistance, and improved device-to-device reproducibility. Water-contact-angle and EDX analyses confirm that COF addition increases surface hydrophobicity and preserves near-ideal Pb:I stoichiometry, supporting enhanced environmental stability. This study introduces bulk COF doping as a simple, scalable strategy to engineer MAPbI3 microstructure, energetics, and surface chemistry in a single processing step, and identifies DMTH-COF as the most effective of the three frameworks. More broadly, it positions COF–perovskite hybrids as a tunable platform for high-efficiency, durable perovskite optoelectronics.
SN  - 2073-4360
ER  -