Despite the high power conversion efficiency (PCE) of perovskite solar cells (PSCs), poor long-term stability is one of the main obstacles preventing their commercialization. Several approaches to enhance the stability of PSCs have been proposed. However, an accelerating stability test of PSCs at high temperature under the operating conditions in ambient air remains still to be demonstrated. Herein, interface-engineered stable PSCs with inorganic charge-transport layers are shown. The highly conductive Al-doped ZnO films act as efficient electron-transporting layers as well as dense passivation layers. This layer prevents underneath perovskite from moisture contact, evaporation of components, and reaction with a metal electrode. Finally, inverted-type PSCs with inorganic charge-transport layers exhibit a PCE of 18.45% and retain 86.7% of the initial efficiency for 500 h under continuous 1 Sun illumination at 85 °C in ambient air with electrical biases (at maximum power point tracking).

Although post-treatment has been regarded as one of the effective ways to passivate the underlying defects in perovskite solar cells (PSCs), little attention has been paid to how to select suitable passivation agents. Here, we report on the dependence of photovoltaic performance on acid dissociation constant (K a) of passivation agents to guide a criterion for selecting passivation agents in PSCs. Power conversion efficiency (PCE) is increased after post-treatment with high-pK a (10.6) cyclohexylammonium chloride (CYCl), whereas low-pK a (4.6) anilinium chloride (ANCl) decreases PCE because of more traps generated adversely by ANCl. Degree of deprotonation (pK a value) is responsible for generation of defect-mediated traps, where relatively more deprotonation from lower-pK a ANCl generates free iodide, resulting in iodide defects. The CYCl-treated FAPbI3 film deposited on a highly transparent FTO substrate shows a reverse-scanned PCE of 24.98%, and 91% of the initial PCE is maintained after storage in the dark for over 1300 h.

Extended understandings of perovskite solar cells by recent ALD application studies as well as challenges toward enhancing the efficiency and stability will be addressed.

High-efficiency planar type perovskite solar cells were fabricated by atomic layer deposition (ALD) of SnO2 and subsequent annealing at 180 °C.

In article number https://doi.org/10.1002/adma.201801010, Nam‐Gyu Park, Hyunjung Shin, and co‐workers present a perovskite solar cell (PSC) composed of fluorine‐doped tin oxide (FTO)/NiO/perovskite/[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM)/bathocuproine (BCP)/Al:ZnO/Ag. They find that the Al:ZnO layer grown via atomic layer deposition plays a significant role in improving the stability of the PSC. The unique role of the Al:ZnO, distinguished from other types of passivation, is its impermeability, which prevents moisture penetration, as well as interdiffusion at the perovskite/Ag interface when illuminated at higher temperature (≈85 °C).