http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/5715 2026-08-13T08:56:33Z 2026-08-13T08:56:33Z Amalraj, P.A. Loheeswaran, S. Landova, L. Neykova, N. Holovský, J. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/12859 2026-08-10T04:58:53Z 2025-01-01T00:00:00Z

Polymer-Assisted Crystallization and Defect Passivation in Planar Wide-Bandgap FAPbBr3 Perovskite Solar Cells Amalraj, P.A.; Loheeswaran, S.; Landova, L.; Neykova, N.; Holovský, J. Wide-bandgap lead bromide perovskites such as FAPbBr 3 are promising candidates for tandem solar cells and high-voltage optoelectronic applications, yet their performance is limited by surface and bulk defects that induce severe nonradiative recombination and limit stability. In this work, we present a defect passivation and crystallization control strategy by incorporating poly­(methyl methacrylate) (PMMA) into the antisolvent during FAPbBr 3 film fabrication. PMMA treatment leads to improved film morphology with larger grains, reduced surface roughness, and enhanced crystallinity. FTIR analysis reveals that the carbonyl groups in PMMA coordinate with undercoordinated Pb 2+ ions, effectively passivating electronic trap states. Photothermal deflection spectroscopy (PDS) shows reduced sub-bandgap absorption and lower Urbach energy, indicating suppressed deep-level defects and reduced energetic disorder. Enhanced photoluminescence intensity, prolonged carrier lifetimes, and decreased trap densities further confirm suppressed nonradiative recombination. As a result, PMMA treatment increases Voc by over 100 mV and improves power conversion efficiency by more than 1%, achieving a Voc of up to 1.510 V with reduced hysteresis and improved ambient stability. These findings demonstrate the effectiveness of polymer-assisted strategies for improving both efficiency and stability of wide-bandgap perovskite solar cells, offering a pathway toward high-voltage and tandem photovoltaic applications.

2025-01-01T00:00:00Z Amalraj, P.A. Horynova, E. Holovsky, J. Landova, L. Jain, N. Pakki, A.D. Kuo, M.H. Pelikánová, I.B, Dzurňák, B. Horák, L. Pop-Georgievski, O. Neda, N. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/12855 2026-08-07T05:04:25Z 2025-01-01T00:00:00Z

Nickel oxide hole transport layer for perovskite solar cells: Preparation via pulsed laser deposition with simulation and experimental insights Amalraj, P.A.; Horynova, E.; Holovsky, J.; Landova, L.; Jain, N.; Pakki, A.D.; Kuo, M.H.; Pelikánová, I.B,; Dzurňák, B.; Horák, L.; Pop-Georgievski, O.; Neda, N. Nickel oxide (NiOx) has gained attention as a promising inorganic hole transport layer for perovskite solar cells due to its wide bandgap, high transparency, and stability. However, tuning of band alignment by an extra dipole layer is necessary to achieve high efficiencies. Our predictive simulations suggest that NiOx bandgap tuning can also improve solar cell performance. Motivated by these findings, this study experimentally investigates NiOx films with different bandgap fabricated using pulsed laser deposition under varying deposition conditions, including oxygen pressure, substrate temperature and laser frequency. Our outcomes show that mainly the deposition temperature significantly influences the chemical composition, optical properties, and defect states in the NiOx films, lattice constants and morphology as confirmed by X-ray photoelectron spectroscopy, photothermal deflection spectroscopy, X-ray diffraction spectroscopy, atomic force microscopy and scanning electron microscopy. Experimentally, FA0.83Cs0.17Pb(I0.6Br0.4)3 mixed halide perovskite solar cells were fabricated on NiOx substrates prepared under varying oxygen pressures and pulse numbers, achieving a maximum power conversion efficiency of approximately 8 %. This demonstrates that NiOx deposited by pulsed laser deposition, when properly tuned, is a promising candidate for an efficient hole transport layer in perovskite-based photovoltaics.

2025-01-01T00:00:00Z Amalraj, P.A. Rajavinayagam, A. Landova, L. Dopita, M. Holovsky, J. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/12854 2026-08-07T04:45:26Z 2025-01-01T00:00:00Z

Synergetic effect of tetraoctylammonium chloride in suppressing photoinduced phase segregation in mixed halide perovskite solar cells Amalraj, P.A.; Rajavinayagam, A.; Landova, L.; Dopita, M.; Holovsky, J. Phase segregation, caused by halide ion migration under illumination, is a critical challenge limiting the commercialization of mixed-halide perovskites. In this study, a facile and effective strategy is introduced to mitigate photoinduced phase segregation in the FA0.83Cs0.17Pb(I0.6Br0.4)3 mixed halide perovskite film by employing tetraoctylammonium chloride (TOAC) as both an additive and surface passivation for the first time. The results demonstrate that TOAC effectively reduces halide ion migration, stabilizes the perovskite phase, and suppresses phase segregation, particularly in the combined additive-passivation configuration. Mixed-halide perovskite solar cells fabricated with this dual TOAC approach achieve the highest efficiency of 15.8 %, with enhanced stability under continuous illumination and reduced hysteresis. The study highlights the critical role of TOAC in suppressing phase segregation, and improving the stability and performance of mixed-halide perovskite solar cells by addressing both surface and bulk defects, facilitating the development of more stable and efficient mixed-halide perovskite solar cells.

2025-01-01T00:00:00Z Abiram, G. HeidariGourji, F. Pitchaiya, S. Ravirajan, P. Murugathas, T. Velauthapillai, D. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/9530 2023-06-07T07:05:28Z 2022-01-01T00:00:00Z

Air processed Cs2AgBiBr6 lead‑free double perovskite high‑mobility thin‑flm feld‑efect transistors Abiram, G.; HeidariGourji, F.; Pitchaiya, S.; Ravirajan, P.; Murugathas, T.; Velauthapillai, D. This study focuses on the fabrication and characterization of Cs2AgBiBr6 double perovskite thin flm for feld-efect transistor (FET) applications. The Cs2AgBiBr6 thin flms were fabricated using a solution process technique and the observed XRD patterns demonstrate no difraction peaks of secondary phases, which confrm the phase-pure crystalline nature. The average grain sizes of the spin-deposited flm were also calculated by analysing the statistics of grain size in the SEM image and was found to be around 412 (± 44) nm, and larger grain size was also confrmed by the XRD measurements. FETs with diferent channel lengths of Cs2AgBiBr6 thin flms were fabricated, under ambient conditions, on heavily doped p-type Si substrate with a 300 nm thermally grown SiO2 dielectric. The fabricated Cs2AgBiBr6 FETs showed a p-type nature with a positive threshold voltage. The on-current, threshold voltage and hole-mobility of the FETs decreased with increasing channel length. A high average hole mobility of 0.29 cm2 ­s−1 ­V−1 was obtained for the FETs with a channel length of 30 µm, and the hole-mobility was reduced by an order of magnitude (0.012 cm2 ­s−1 ­V−1) when the channel length was doubled. The on-current and hole-mobility of Cs2AgBiBr6 FETs followed a power ft, which confrmed the dominance of channel length in electrostatic gating in Cs2AgBiBr6 FETs. A very high-hole mobility observed in FET could be attributed to the much larger grain size of the Cs2AgBiBr6 flm made in this work.

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