Examinando por Autor "Lamminaho, Jani"

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Identification of Degradation Mechanisms in Slot-Die-Coated Nonfullerene ITO-Free Organic Solar Cells Using Different Illumination Spectra
(ACS, 2020-07-27) Arredondo, Belén; del Pozo, Gonzalo; Hernández-Balaguera, Enrique; Martin-Martin, Diego; López-Gonzalez, Maria del Carmen; Romero, Beatriz; Lopez-Fraguas, Eduardo; Vergaz, Rcardo; Quintana, Xabier; Lamminaho, Jani; Destouesse, Elodie; Ahmadpour, Mehrdad; Turkovic, Vida; Madsen, Morten
In this work, we have studied degradation mechanisms of nonfullerene-based organic solar cells with PET/Ag/ZnO/ PBDTB-T:ITIC/PEDOT:PSS/CPP PEDOT:PSS device structure. We compare pristine and degraded samples that were subjected to outdoor degradation following the standard ISOS-O2 protocol. The ideality factors for different incident wavelengths obtained from open-circuit voltage vs irradiation level and current density-voltage (J-V) measurements at different temperatures indicate that for aged samples recombination is governed by the Shockley-Read-Hall mechanism occurring in a region near the anode. Samples were also characterized using impedance spectroscopy (IS) and fitted to an electrical model. Impedance parameters were used to obtain mobility, indicating a clear degradation of the active layer blend for aged samples. The change in the chemical capacitance also reveals a worsening in carrier extraction. Finally, two-dimensional (2D) numerical simulations and fits to experimental J-V curves confirm the existence of a layer near the anode contact with poorer mobility and a decrease in the anode work function (WF) for the degraded samples.
Influence of solvent additive on the performance and aging behavior of non-fullerene organic solar cells
(Elsevier, 2022) Arredondo, Belén; Pérez-Martínez, José Carlos; Muñoz-Díaz, Laura; López-González, Maria del Carmen; Martín-Martín, Diego; Pozo, Gonzalo del; Hernández-Balaguera, Enrique; Romero, Beatriz; Lamminaho, Jani; Turkovic, Vida; Madsen, Morten
The performance of organic solar cells has improved significantly in recent years due to the use of non-fullerene acceptors (NFA). While processing additives are typically added to the active layer blends to enhance device performance in NFA organic solar cells, their impact on device degradation remains unclear. In this work we have compared the performance, in pristine and degraded state, between air-processed slot-die coated NFA ITOfree organic solar cells with and without the processing additive DIO, using a structure of PET/Ag/ZnO/PBDB-T: ITIC/FHC PEDOT:PSS. We observed an improvement in the power conversion efficiency of the devices when adding DIO, from 4.03% up to 4.97%. The evolution of the performance for both devices under ISOS-L1 life testing protocol reveals that the drop in efficiency is mainly due to a decay of JSC for both cells. In the short time scale the efficiency of non-DIO cells decays faster than the DIO cells, whereas in the long time scale the efficiency of non-DIO cells tends to stabilize sooner. Carrier mobilities estimated from impedance measurements decrease with time at similar rate for both degraded samples. Besides, DIO devices present a steep increase of the series resistance with time causing a decrease of the FF and thus of the efficiency. Moreover, in both degraded devices, the open-circuit voltage saturates with increasing illumination intensity. Numerical simulations reveal that a reduced anode work function of 5 eV is needed to fit experimental data.