@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{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} } @misc{KotKegelmannKoebleretal., author = {Kot, Małgorzata and Kegelmann, Lukas and K{\"o}bler, Hans and Vorokhta, Mykhailo and Escudero, Carlos and K{\´u}š, Peter and Šm{\´i}d, Břetislav and Tallarida, Massimo and Albrecht, Steve and Abate, Antonio and Matol{\´i}nov{\´a}, Iva and Schmeißer, Dieter and Flege, Jan Ingo}, title = {In situ Near-Ambient Pressure X-ray Photoelectron Spectroscopy Reveals the Influence of Photon Flux and Water on the Stability of Halide Perovskite}, series = {ChemSusChem}, volume = {13}, journal = {ChemSusChem}, number = {21}, issn = {1864-5631}, doi = {10.1002/cssc.202001527}, pages = {5722 -- 5730}, abstract = {For several years, scientists have been trying to understand the mechanisms that reduce the long-term stability of perovskite solar cells. In this work, we examined the effect of water and photon flux on the stability of CH3NH3PbI3 perovskite films and solar cells using in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), field emission scanning electron microscopy (FESEM), and current density-voltage (J-V) characterization. The used amount of water vapor (up to 1 mbar) had a negligible impact on the perovskite film. The higher the photon flux, the more prominent were the changes in the NAP-XPS and FESEM data; also, a faster decline in power conversion efficiency (PCE) and a more substantial hysteresis in the J-V characteristics were observed. Based on our results, it can be concluded that the PCE decrease originates from the creation of Frenkel pair defects in the perovskite film under illumination. The stronger the illumination, the higher the number of Frenkel defects, leading to a faster PCE decline and more substantial hysteresis in the J-V sweeps.}, language = {en} } @misc{KotDasKegelmannetal., author = {Kot, Małgorzata and Das, Chittaranjan and Kegelmann, Lukas and K{\"o}bler, Hans and Vorokhta, Mykhailo and Escudero, Carlos and Albrecht, Steve and Abate, Antonio and Flege, Jan Ingo}, title = {Application of atomic layer deposition and x-ray photoelectron spectroscopy in perovskite solar cells}, series = {Verhandlungen der DPG}, journal = {Verhandlungen der DPG}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, abstract = {In this work we have utilized near-ambient pressure and ultra-high vacuum X-ray photoelectron spectroscopy as well as atomic layer deposition to investigate perovskite solar cells (PSCs). We have demonstrated that ultrathin room temperature atomic layer-deposited aluminium oxide on the perovskite surface very effectively suppresses iodine migration[1] and improves the long term stability and efficiency of PSCs [2,3]. Furthermore, exposure to light proves more detrimental to the perovskite film than exposure to water vapor.[2] Absorbed photons create Frenkel defects in the perovskite crystal and their number strongly depends on the used illumination. The higher the photon flux, the higher the concentration of Frenkel defects, and thus the stronger the degradation of power conversion efficiency and the stronger the hysteresis in the J-V characteristics. [1] C. Das, M. Kot et al., Cell Reports Physical Science 2020, 1, 100112. [2] M. Kot et al., ChemSusChem 2020, 13, 5722. [3] M. Kot et al., ChemSusChem 2018, 11, 3640.}, language = {en} }