Teams:
Project Director: PhD. Lucia Nicoleta Leonat
Mentor: Prof. Stefan Antohe

Stage I. Optimization of the p-type selective layer
At this stage of the project, in accordance with the proposed objectives, the following activities were successfully carried out:
- obtaining and characterizing PEDOT:PSS layers, using a surfactant to help form continuous and homogeneous thin films;
- study of p-type polymers, poly (N-vinylcarbazole) (PVK) and poly (9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4 ′-(N (4-sec-butylphenyl)) diphenylamine (TFB), in the form of thin films that will be used as interlayers between PEDOT:PSS and perovskite, to obtain solar cells with improved efficiency;
- study of the perovskite film fabricated over these polymeric films to be integrated in the devices.

Stage II. Study and optimization of the interface between the p-type selective layer and perovskite. Optimization of the perovskite photoactive layer
At this stage of the project, in accordance with the proposed objectives, the following activities were successfully carried out:
- preparation of samples with different films of p-type polymers and study of the excitonic dissociation at the interface with perovskite by photoluminescence spectroscopy methods. The materials used were p-type polymers analyzed in the previous stage of the project: PEDOT: PSS, PVK, TFB to which another p-type material was later added: N, N′-Bis (3-methylphenyl) -N, N ′ -diphenylbenzidine (TPD) due to its properties close to those of PVK and TFB and favorable energy levels. The best results were obtained when PVK and TPD were used as interlayers between PEDOT:PSS and perovskite;

- preparation of samples for which perovskite films were spun over different layers of p-type polymers and study of their quality by X-ray diffraction and electron microscopy. It was observed that on all substrates containing p-type polymeric films, perovskite arranges well, forming crystalline, compact and homogeneous films;
- the study of the quality and stability of the perovskite photoactive layer was carried out, focusing on the migration of ions at the interface with the p-type material using XPS analysis. The samples with PVK and TPD show the lowest amount of type I ions 3d, Pb 4f, and Au 4f, thus indicating the highest stability of the perovskite structure for these two polymers;
- preparation of samples with 3 different types of n-type polymers on top of perovskite and study of their morphology using SEM microscopy. Materials used for n-type films were: [60] PCBM (6,6) -Phenyl-C61 Butyric Acid Methyl Ester (PCBM), tris (8-hydroxyquinoline) aluminum (Alq3), bathocuproine (BCP).

1.  V. Stancu, L.N. Leonat, A.G. Tomulescu, S. Derbali, L. Pintilie, C. Besleaga, A.C. Galca , F. Neatu, S. Neatu, M. Florea, I. Pintilie, “Influence of doping the inorganic cation with Eu or Sb on the properties of perovskite films”, Physica Scripta, 2020, 95, 075707 (9pp), https://doi.org/10.1088/1402-4896/ab90be;
2. G. Tomulescu, V. Stancu, C. Beşleagă, M. Enculescu, G. A. Nemneş, M. Florea, V. Dumitru, L. Pintilie, I. Pintilie, L. Leonat, „Reticulated Mesoporous TiO2 Scaffold, Fabricated by Spray Coating, for Large‐Area Perovskite Solar Cells”, Energy Technology 2019, Vol 7, p 1900922-190033, https://doi.org/10.1002/ente.201900922;\
3. Derbali, K. Nouneh, M. Florea, F. Neatu, S. Neatu, L. Leonat, M. Secu, A.G. Tomulescu, V. Stancu, L. Pintilie, M.E. Touhami, M. Ebn, A.C. Galca, “Exploring the effect of aliovalent substitution of Pb²⁺ by Eu³⁺ on structural, morphological and optical properties of CH₃NH₃PbI₃ perovskite films”, Physica Scripta, 95, 4, 2020, https://doi.org/10.1088/1402-4896/AB5BAA.

Other papers in the field:

1. Philipp Stadler, Lucia N. Leonat, Reghu Menon, Halime Coskun, Sandrine van Frank, Christian Rankl, Markus C. Scharber „Stable Hall voltages in presence of dynamic quasi-continuum bands in poly(3,4-ethylene-dioxythiophene)”, Organic Electronics (2019), DOI: https://doi.org/10.1016/j.orgel.2018.12.001;

Conferences:

1.    “18th International Balkan Workshop on Applied Physics and Materials Science- IBWAP 2018” Constanţa, 10 – 13 July 2018, posters:

ü   Organic cation engineering for improved perovskite based solar cells,  Lucia N. Leonat, Andrei Tomulescu, Viorica Stancu, Mihaela Florea, Florentina Neaţu, Ştefan Neaţu, Sarah Derbali, Vasilica Toma, Ionel Mercioniu, Lucian Pintilie, Ioana Pintilie;

ü   Studies on the enhancement of electrical conductivity in PEDOT:PSS films, Lucia N. Leonat, Florentina Neaţu, Mihaela Florea, Viorica Stancu, Andrei Tomulescu, Ionel Mercioniu, Ioana Pintilie, Ştefan Antohe.

2.    Talk: Perovskite Solar Cells – Latest developments at NIMP, Lucia N. Leonat, Andrei Tomulescu, Viorica Stancu, Sarah Derbali, Mihaela Florea, Florentina Neatu, Monica Enculescu, Ionel Mercioniu, Ioana Pintilie, la Sesiunea de comunicari interne a INCDFM desfasurata la IFIN-HH, in perioada 6 – 8 iunie 2018;

3.    Poster: Synthesis and properties of C₃N₂H₅PbI₃ powders as precursors for hybrid perovskite based solar cells, Mihaela Florea, Florentina Neaţu, Stefan Neațu, Cristina Mozăceanu, Sarah Derbali, Cristina Bartha, Lucia N. Leonat, Andrei G. Tomulescu, Viorica Stancu, Vasilica Toma, Ioana Pintilie, la The 7th EuCheMS Chemistry Congress, Molecular frontiers & global challenges, 26–30 August 2018, ACC Liverpool, Marea Britanie;

4.    Talk: Defects in perovskite solar cells, Lucia N. Leonat,  Andrei Tomulescu, Viorica Stancu, Mihaela Florea, Florentina Neatu, Stefan Neatu, Cristina Besleaga Stan,  Ioana Pintilie, Stefan Antohe, la International Workshop on Advances in Nanomaterials, 17-21 Septembrie 2018, organizat de Institutul National pentru Fizica Materialelor și International Center for Training and Advanced Research (Centre International de Formation et Recherche Avancee - CIFRA);

5.    Poster: Surface studies on the PEDOT:PSS films modified with Triton-X 100 surfactant, autori Lucia N. Leonat, Florentina Neatu, Andrei Tomulescu, Mihaela Florea, Viorica Stancu, Ştefan Neaţu, Ioana Pintilie, Ştefan Antohe, International Conference “IUPAC Chemistry Congress” - IUPAC 2019” , 5 – 13 July 2019, Paris, France.

6.  Poster: Hole-Transport Interlayers for Planar Perovskite Solar Cells, autori Lucia N. Leonat, Florentina Neatu, Bekele Teklemariam Hailegnaw, Andrei Tomulescu, Mihaela Florea, Viorica Stancu, Ioana Pintilie, Markus Clark Scharber, Ştefan Antohe, Lucian Pintilie, "NanoGe International Conference on Perovskite Solar Cells, Photonics and Optoelectronics", 23-25 February 2020, Seville, Spain.