@inproceedings{KotKegelmannKusetal., author = {Kot, Małgorzata and Kegelmann, Lukas and Kus, Peter and Tsud, Nataliya and Matol{\´i}nov{\´a}, Iva and Albrecht, Steve and Matolin, Vladimir and Schmeißer, Dieter}, title = {Room temperature atomic layer deposition for perovskite solar cells}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 174}, abstract = {After few years of efficiency driven research on perovskite solar cells, the focus now is shifting to understand the underlying processes governing the high efficiency and also to obtain long-term stable devices. Among various deposition methods, atomic layer deposition (ALD) may represent one of the best options, being possible to coat substrates in a very efficient way and at very low temperatures. In our previous work [1] we reported that the efficiency of the solar cell containing aged perovskite film can be enhanced twice while covering the perovskite with a thin ALD alumina film at room temperature. In this work, the chemical, electronic and morphological properties of the fresh perovskite film treated by ALD pulses of the trimethylaluminium and water at room temperature investigated using X-ray Photoelectron Spectroscopy and Field Emission Scanning Electron Microscopy will be discused and correlated with the solar cells performance and stability. [1] M. Kot et al., ChemSusChem 2016, 9, 3401.}, language = {en} } @misc{KotKegelmannDasetal., author = {Kot, Małgorzata and Kegelmann, Lukas and Das, Chittaranjan and Kus, Peter and Tsud, Nataliya and Matol{\´i}nov{\´a}, Iva and Albrecht, Steve and Matolin, Vladimir and Schmeißer, Dieter}, title = {Room temperature atomic layer deposited Al₂O₃ improves perovskite solar cells efficiency over time}, series = {ChemSusChem}, volume = {11}, journal = {ChemSusChem}, number = {20}, issn = {1864-5631}, doi = {10.1002/cssc.201801434}, pages = {3640 -- 3648}, abstract = {Electrical characterisation of perovskite solar cells consisting of room-temperature atomic-layer-deposited aluminium oxide (RT-ALD-Al₂O₃) film on top of a methyl ammonium lead triiodide (CH₃NH₃PbI₃) absorber showed excellent stability of the power conversion efficiency (PCE) over along time. Under the same environmental conditions (for 355 d), the average PCE of solar cells without the ALD layer decreased from 13.6 to 9.6 \%, whereas that of solar cells containing 9 ALD cycles of depositing RT-ALD-Al₂O₃on top of CH₃NH₃PbI₃ increased from 9.4 to 10.8 \%. Spectromicroscopic investigations of the ALD/perovskite interface revealed that the maximum PCE with the ALD layer is obtained when the so-called perovskite cleaning process induced by ALD precursors is complete. The PCE enhancement over time is probably related to a self-healing process induced by the RT-ALD-Al₂O₃ film. This work may provide a new direction for further improving the long-term stability and performance of perovskite solar cells.}, language = {en} } @misc{SchmeisserHenkelPożarowskaetal., author = {Schmeißer, Dieter and Henkel, Karsten and Pożarowska, Emilia and Kegelmann, Lukas and Tsud, Nataliya and Kot, Małgorzata}, title = {Point Defect-Mediated Interface Formation and Appearance of a Cooper Minimum for AlOₓ Atomic-Layer-Deposited Films on CH₃NH₃PbI₃}, series = {The Journal of Physical Chemistry. C}, volume = {123}, journal = {The Journal of Physical Chemistry. C}, number = {38}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.9b05282}, pages = {23352 -- 23360}, abstract = {We report on the interaction of CH₃NH₃PbI₃ substrates with AlOx films prepared by atomic layer deposition at room temperature. We use synchrotron radiation-based photoemission spectroscopy and study the Pb 4f, I 3d, and Al 2p core levels as well as the corresponding valence band states (Pb 5d and O 2p). A Cooper minimum is observed for both the Pb 5d and O 2p states, and it indicates that the bonding at the interface must be covalent. We focus on the electronic properties of the substrate and its interface and identify a delicate charge balance between polaronic and excitonic states in MAPI and AlOₓ. The perovskite vacancy sites, identified by changes in the core-level intensities, mediate the charge balance and covalent interaction.}, language = {en} } @misc{KotHenkelMuelleretal., author = {Kot, Małgorzata and Henkel, Karsten and M{\"u}ller, Klaus and Kegelmann, Lukas and Albrecht, Steve and Tsud, Nataliya and K{\´u}s, Peter and Matolinov{\´a}, Iva and Schmeißer, Dieter}, title = {Al2O3-Atomic Layer Deposited Films on CH3NH3PbI3 : Intrinsic Defects and Passivation Mechanisms}, series = {Energy Technology , The Journal of Physical Chemistry C}, volume = {7}, journal = {Energy Technology , The Journal of Physical Chemistry C}, number = {11}, issn = {2194-4288}, doi = {10.1002/ente.201900975}, pages = {10}, abstract = {The initial interaction of atomic layer deposited films of Al2O3 at room temperature on CH3NH3PbI3 (MAPI) films is studied. Synchrotron radiation-based photoelectron spectroscopy is applied to analyze the initial changes in the Al-derived features by comparing samples with different Al2O3 film thicknesses. It is found that polarons and excitons, both intrinsic defects of Al2O3, play a key role in the interface formation. The polaronic states uptake a charge from the MAPI substrate. This charge is transferred to and stabilized in the excitonic state of Al2O3 which is assigned to predominately tetrahedral coordinated Al sites. This charge transfer is initiated by vacancies present in the MAPI substrate and stabilizes a covalent bonding at the Al2O3-MAPI interface but also causes a roughening of the interface which may lead to the formation of grain boundaries. On top of the rough interface, 2D Al2O3 clusters with an increasing number of octahedrally coordinated Al—O bonds grow, and with increasing Al2O3 coverage, they introduce self-healing of the structural defects.}, language = {en} }