Room‐Temperature Atomic‐Layer‐Deposited Al₂O₃ Improves the Efficiency of Perovskite Solar Cells over Time

Abstract

Electrical characterisation of perovskite solar cells consisting of room-temperature atomic-layer-deposited aluminium oxide (RT-ALD-Al O ) film on top of a methyl ammonium lead triiodide (CH NH PbI ) absorber showed excellent stability of the power conversion efficiency (PCE) over a long 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-Al O on top of CH NH PbI 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-Al O film. This work may provide a new direction for further improving the long-term stability and performance of perovskite solar cells.

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

“…Continuing the ALD growth with more than 25 cycles, the Al 2 O 3 film is conformal, sealing that roughened interface again. A detailed analysis of secondary electron microscopy images is given in a previous study, confirming atomic force microscopy (AFM) images as discussed in another previous study.…”

“…These are promising properties for an ideal passivation layer and a good basis for increased long‐term stabilities of perovskite‐based solar cells. The influence of the Al 2 O 3 layer on the optical and electrical properties is already reported, but still details need further experimental studies to correlate it with the influence of charge separation or recombination processes.…”

“…From the derived data, we deduce a model in which we suggest that in the RT‐prepared Al 2 O 3 films on MAPI, the growth mechanism differs from the other substrates. The reactive interaction of Al 2 O 3 with the MAPI substrate causes an initial surface etching process . We find that the spatial distribution of vacancies at the interface causes a microscopic roughening by the formation of grain boundaries (GBs).…”

“…To prepare the abovementioned passivation layers for the hybrid perovskite MAPI films, we established an ALD method to deposit Al 2 O 3 films at room temperature (RT). Such films are grown directly on the MAPI surfaces without pretreatment; in particular, there is no need for an OH‐covered surface preparation . As a consequence, MAPI‐based PV devices showed recently an increase in long‐term stability and a protection against ambient conditions upon growth of ALD films of Al 2 O 3 at RT .…”

Stability and Dark Hysteresis Correlate in NiO‐Based Perovskite Solar Cells

“…[60] We modified a low-temperature process for MgO reported previously in literature [61] (Figure S7, Supporting Information), and we achieved complete suppression of the noncapacitive hysteresis without reducing device efficiency, as shown in Figure 3c,d. [60] We modified a low-temperature process for MgO reported previously in literature [61] (Figure S7, Supporting Information), and we achieved complete suppression of the noncapacitive hysteresis without reducing device efficiency, as shown in Figure 3c,d.…”