The importance of understanding the growth fundamentals of ZnO/TiO2nanolaminate structures deposited by atomic layer deposition is explored.

This study focuses on class III peroxidases (POD) (EC 1.11.1.7) as regulators of cellular H2O2 levels in leaves under oxidative stress. The effective regulation of reactive oxygen species (ROS) concentrations in plant tissues is crucial for plant survival, and has been extensively reviewed. However, the majority of studies regard POD as a generalist without substrate specificity. This is partly due to the fact that laboratory protocols assessing POD levels use substrates, which are not contained in plants. Here, we show that both base- and stress-inducible POD activity depends on the choice of substrate. Moreover, the application of diverse substrates, particularly those contained in plants, unmasks POD isoenzymes that are distinguished by substrate preferences. This functional heterogeneity of POD responses is worth studying, especially in parallel with stress-induced changes in the phenolic profiles.

Background To stimulate how to move the field of plant-UV research forward, and create a coherent framework to highlight valuable future directions in plant UV research we had a group discussion of the most prescient questions and how to address them. The following sections are broken-down into those from the molecular, biochemical and physiological discussions followed by those from the ecological and plant production discussions. In each case, first basic research questions are considered and then applications and methodological considerations put forward. Finally, some common ground bringing together the two perspectives is proposed, aimed at solving scaling problems and ways in which the UV4Plants network might be put to good use.

Pulsed chemical vapor deposition (CVD), or more correctly atomic layer deposition (ALD) outside of the ALD thermal window, was used to grow vanadium pentoxide films using Tetrakis(dimethylamino)vanadium (IV) (V(NMe2)(4)) as the vanadium source and either oxygen-argon plasma, oxygen or water as the co-reagent. Growths were performed at 150-300 degrees C for 400 cycles, resulting in a range of both stoichiometric and non-stoichiometric vanadium oxides. Post growth annealing in air at 400 degrees C for both thermal and plasma assisted methods resulted in the formation of alpha-V2O5. Electrochemical characterization revealed that the samples grown at 250 degrees C using a plasma process and a post growth anneal demonstrate the best electrochemical properties in terms of current density and charge density with values of 0.35 mAcm(-2)and 55 mCcm(-2) respectively. The influence of growth parameters on material properties is discussed.

Organometallic halide perovskite solar cells have gained considerable interest in recent times, with low cost and high power conversion efficiencies [1]. However, such cells are not without problems such as, stability, scalability and the need for a low thermal budget in the fabrication of tandem structures. In this work, we examine the transparent conducting electrode where the current materials of choice are FTO and ITO which require a higher process temperature (>450oC). Zinc oxide thin films have attracted significant attention as transparent conducting oxides due to their diverse electrical and optical properties. ZnO is an n-type semiconductor with a direct band gap of 3.3 eV. It is optically transparent in the UV/visible and infrared spectra and exhibits promising electrical properties. ALD has distinct characteristics that make it a prospective deposition method of ZnO and doped ZnO, low temperature, conformal and large surface area coating capabilities. The deposition of ZnO and doped ZnO has previously been reported. In this work, an ALD process has been developed to deposit ZnO as a potential TCO in solar cells. ZnO was deposited using low temperature atomic layer deposition (ALD). Subsequently, zinc oxide was doped with Al, Ti and Hf and the electrical, optical and structural properties were analyzed to determine the effect of doping on ZnO. The presented results revealed that Ti-doped ZnO was the suitable TCO candidate with a sheet resistance value of 41 Ω/□ and electron mobility of 12.8 cm2/Vs. In addition to promising electrical properties, Ti-doped ZnO also exhibited high optical transparency of >80% in the UV/ visible and IR ranges. We demonstrate that ALD of Ti-doped ZnO could be a viable alternative to ITO and FTO for TCO materials in photovoltaics. Preliminary data from perovskite solar cells fabricated with a ZnO based transparent conducting electrode are presented and discussed. [1] https://www.nrel.gov/pv/assets/images/efficiency-chart.png

Pulse chemical vapour deposition (CVD), or more correctly atomic layer deposition (ALD) outside of the ALD thermal window, was used to grow vanadium pentoxide films using Tetrakis(dimethylamino)vanadium (IV) (V(NMe2)4) as the vanadium source and either oxygen-argon plasma, oxygen or water as the co-reagent. Growths were performed at 150-300°C for 400 cycles, resulting in a range of both stoichiometric and non-stoichiometric vanadium oxides. Post growth annealing in air at 400°C for both thermal and plasma assisted methods resulted in the formation of orthorhombic α – V2O5. Electrochemical characterization revealed that the samples grown at 250°C using a plasma process and a post growth anneal demonstrate the best electrochemical properties in terms of current density and charge density with values of 0.35 mAcm-2and 55 mCcm-2 respectively. In addition, the samples grown under these conditions also possess the best electrochromic response, exhibiting a change in percentage transmission between the bleached and coloured states of 65%. The influence of growth parameters on material properties is discussed.

Over the past few years single junction perovskite solar cells have been extensively studied with reported power conversion efficiencies approaching 20% [1-3]. Despite such advances, high efficiency combined with low fabrication cost, parasitic absorptions and long term stability have remained issues. One approach to curtail some of these obstacles has been the investigation of planar architectures where the mesoporous TiO2/Al2O3 is removed from the cell and the electron transport layer (ETL) is reduced to a nanometre scale compact charge blocking layer [4]. Typically this layer has been TiO2 but more recently band gap engineering studies have shown that SnO2 has significant potential in removing TiO2 hysteresis effects whilst maintaining efficiencies [5] In this study we examined planar stacks comprising glass/FTO/ETL/perovskite/spiro MeOTAD hole transport layer/contacts with an aim to further optimize the metal oxide ETL. The metal oxides studied in this work were atomic layer deposition grown SnO2, nominally undoped TiO2 and doped TiO2, all grown at temperatures below 180°C to align with the requirements of silicon-perovskite heterojunction cells [6]. The influence of the ALD growth parameters and composition of the ETL on the subsequent perovskite deposition, as well as the resultant cell performance are highlighted and discussed in terms of efficiency and hysteresis. W.S. Yang et al., Science, 348, 1234-1237 (2015). N.J. Jeon et al., Nature, 517, 476- 480, (2015). S.D. Stranks et al., Science 342, 341-344, (2013) M. Liu et al., Nature, 501, 395- 398, (2013). J.P. Correa Baena, Energy and Environment Science, DOI:10.1039/c5ee02608c, (2015). J.P. Mailoa et al., Applied Physics Letters, 106, 121105 (2015).