@misc{DasRoyKediaetal., author = {Das, Chittaranjan and Roy, Rajarshi and Kedia, Mayank and Kot, Małgorzata and Zuo, Weiwei and F{\´e}lix, Roberto and Sobol, Tomasz and Flege, Jan Ingo and Saliba, Michael}, title = {Unraveling the Role of Perovskite in Buried Interface Passivation}, series = {ACS Applied Materials \& Interfaces}, volume = {15}, journal = {ACS Applied Materials \& Interfaces}, number = {48}, issn = {1944-8244}, doi = {10.1021/acsami.3c13085}, pages = {56500 -- 56510}, abstract = {Interfaces in perovskite solar cells play a crucial role in their overall performance, and therefore, detailed fundamental studies are needed for a better understanding. In the case of the classical n-i-p architecture, TiO2 is one of the most used electron-selective layers and can induce chemical reactions that influence the performance of the overall device stack. The interfacial properties at the TiO2/perovskite interface are often neglected, owing to the difficulty in accessing this interface. Here, we use X-rays of variable energies to study the interface of (compact and mesoporous) TiO2/perovskite in such a n-i-p architecture. The X-ray photoelectron spectroscopy and X-ray absorption spectroscopy methods show that the defect states present in the TiO2 layer are passivated by a chemical interaction of the perovskite precursor solution during the formation of the perovskite layer and form an organic layer at the interface. Such passivation of intrinsic defects in TiO2 removes charge recombination centers and shifts the bands upward. Therefore, interface defect passivation by oxidation of Ti3+ states, the organic cation layer, and an upward band bending at the TiO2/perovskite interface explain the origin of an improved electron extraction and hole-blocking nature of TiO2 in the n-i-p perovskite solar cells.}, language = {en} } @misc{TallaridaAdelmannDelabieetal., author = {Tallarida, Massimo and Adelmann, Christoph and Delabie, Annelies and van Elshocht, Sven and Caymax, Matty and Schmeißer, Dieter}, title = {GaAs clean up studied with synchrotron radiation photoemission}, series = {IOP Conference Series : Materials Science and Engineering}, journal = {IOP Conference Series : Materials Science and Engineering}, number = {41}, issn = {1757-899X}, doi = {10.1088/1757-899X/41/1/012003}, pages = {012003}, abstract = {In this contribution we describe the chemical changes at the surface of GaAs upon adsorption of tri-methyl-aluminum (TMA). TMA is used to grow Al2O3 with atomic layer deposition (ALD) usually using H2O as oxygen source. Recently, it was pointed out that the adsorption of TMA on various III-V surfaces reduces the native oxide, allowing the growth of an abrupt III-V/High-K interface with reduced density of defects. Synchrotron radiation photoemission spectroscopy (SR-PES) is a powerful method to characterize surfaces and interfaces of many materials, as it is capable todetermine their chemical composition as well as the electronic properties. We performed in-situ SR-PES measurements after exposing a GaAs surface to TMA pulses at about 250°C. Upon using the possibility of tuning the incident photon energy we compared the Ga3d spectra at 41 eV, 71 eV, 91 eV and 121 eV, as well as the As3d at 71 eV and 91 eV. Finally, we show that using SR-PES allows a further understanding of the surface composition, which is usually not accessible with other techniques.}, language = {en} }