On the effect of atomic layer deposited Al₂O₃ on the environmental degradation of hybrid perovskite probed by positron annihilation spectroscopy

Abstract

Doppler broadening-positron annihilation spectroscopy (DB-PAS) provides insights into the structural degradation of pristine and ALD Al2O3 capped CH3NH3PbI3−xClx under ambient air exposure.

Photochromic YOxHy Thin Films Examined by <i>in situ</i> Positron Annihilation Spectroscopy

“…Recently, we investigated various types of functional layers for thin film solar cells, including CdSe quantum dot (QD) layers for QD-based solar cells [1], demonstrating that the high sensitivity of positrons to detect surface properties of the QDs stems from the presence of a positron surface state. The degradation of ZnO/Cu(In,Ga)Se 2 [2] and of methyl ammonium lead iodide (MAPbI 3 ) perovskite solar cells [3] was linked to the in-diffusion of water molecules and to the interplay of the subsequently occurring chemical reactions and vacancies in the ZnO and MAPbI 3 layers. Finally, PAS is very useful for the investigation of hydrogen energy materials, such as Mg 1−y Ti y H 2 thin films [4].…”

Barrier Designs in Perovskite Solar Cells for Long‐Term Stability

“…Insulting ALD-Al 2 O 3 has been demonstrated to be efficient barriers. [179][180][181][182][183] For example, Koushik et al deposited an ultra-thin (≈2 nm) Al 2 O 3 layer on top of the MAPbI 3−x Cl x perovskite using the ALD method to enhance the resistance of PSC to moisture (Figure 7f). It should be noted that this moisture barrier is required to be thin enough to allow the tunneling of carriers.…”

Al2O3‐Atomic Layer Deposited Films on CH3NH3PbI3: Intrinsic Defects and Passivation Mechanisms

“…The interface between chlorine‐doped MAPI and an Al 2 O 3 ALD layer (prepared at 80 °C) was studied recently by Koushik et al When the perovskite was exposed to air, degradation involving changes in its open volumes and crystal lattice probably caused by the ingress of H 2 O molecules into cation vacancies accompanied by chemical changes and thickness reduction was observed, which could be suppressed or at least delayed by an ultrathin (<1 nm) Al 2 O 3 ALD layer . Furthermore, the authors found that no diffusion of the ALD precursor and coreactant (trimethylaluminium (TMA) and water) into the perovskite and no oxidation of the inorganic framework took place . Rather, a growth mechanism, where TMA interacts with the CH 3 NH 3 + cation releasing CH 3 NH 2 and CH 4 and leaving behind a PbI 3 −Al(CH 3 ) 2 complex which further reacts with water in the subsequent ALD semi‐cycle, is proposed .…”

“…Furthermore, the authors found that no diffusion of the ALD precursor and coreactant (trimethylaluminium (TMA) and water) into the perovskite and no oxidation of the inorganic framework took place . Rather, a growth mechanism, where TMA interacts with the CH 3 NH 3 + cation releasing CH 3 NH 2 and CH 4 and leaving behind a PbI 3 −Al(CH 3 ) 2 complex which further reacts with water in the subsequent ALD semi‐cycle, is proposed . Accordingly, an OH‐generated surface for further Al 2 O 3 growth is generated.…”

“…Accordingly, an OH‐generated surface for further Al 2 O 3 growth is generated. However, this growth is attenuated up to a thickness of about 5 nm; just beyond it, the typical linear growth mode starts …”