In the current work, we studied the effect of the passivation of atomic layer deposited (ALD) ultrathin TiO2 on hydrothermally grown one-dimensional (1D) TiO2 nanorod (NR) arrays for solid-state perovskite-sensitized solar cells. Different thicknesses of ALD-passivated TiO2 were deposited on the hydrothermally grown 1D TiO2 NR samples. The ALD TiO2 thickness was varied from 1 to 5 nm by variation of the growth cycle. Our controlled results revealed that the 4 nm thin-layer-passivated TiO2 NR sample shows a power conversion efficiency (PCE) as high as η = 12.53% (without masking) for the CH3NH3PbI3 perovskite absorbing layer. Our results revealed that the solar cell performance with different ALD passivation thicknesses strongly affects the open-circuit voltage (V OC) as well as the short-circuit current density (J SC). However, compared with high-temperature-processed standard device configurations based on TiCl4-treated mesoporous TiO2 (mp-TiO2) (∼10%) and TiCl4-treated TiO2 NR (∼9%) perovskite solar cells, our low-temperature-processed, pinhole-free ALD-passivated devices exhibit higher PCEs. The 4 nm passivated sample exhibits η = 12.53 ± 0.35% with J SC = 19.23 ± 0.53 mA cm–2, fill factor (FF) = 0.70 ± 0.4, and V OC = 0.931 ± 0.01 V. By control of the ultrathin passivation layer thickness, our champion cell with 4.8 nm ALD passivated TiO2 NRs demonstrated a PCE of 13.45% with J SC = 19.78 mA cm–2, V OC = 0.945 V, and FF = 0.72. These results further emphasize hydrothermally grown 1D TiO2 and ALD-passivated electron transporting layers (ETLs) for efficient perovskite solar cell applications.

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The possibility of employing molecular oxygen (O2) for reducing the carrier concentration of zinc oxide (ZnO) thin films grown by atomic layer deposition was investigated. The exposure of O2 after the oxygen‐source pulse (deionised water) was eventually highly effective for decreasing the carrier concentration over 3–4 orders of magnitude. In contrast, the O2 pulse, when following the zinc source pulse (diethylzinc), had a minimal effect on the electrical property. Detailed structural, chemical and electrical analyses of the oxygen‐modulated ZnO thin films were conducted. Successful electrical modulation of the ZnO thin films was further demonstrated by fabricating back‐gated thin film transistors. The improvement in the on‐to‐off current ratio of the transistors was achieved by the proper exposure of O2.

This study examined the effect of sputtering power on the performance of zinc-tin-oxide field-effect transistors and the stability under photobias stress. Large improvements in the saturation mobility and subthreshold swing were found in devices fabricated at higher sputtering powers; 13.80 cm 2 /VÁs, 0.33 V/decade at a power of 400 W compared with 2.70 cm 2 /VÁs, 1.19 V/decade at a power of 50 W. The threshold voltage shift under negative bias illumination stress (NBIS) for the device fabricated at a power of 400 W shows superior properties (À2.41 V) compared with that (À5.56 V) of the device fabricated at 50 W. The improvements in electrical performance and NBIS stability were attributed to the formation of a denser film and the reduced dielectric/channel interfacial trap densities due to the more energetic bombardment used under high power sputtering conditions.