Efficient Polymer Solar Cells Enabled by Low Temperature Processed Ternary Metal Oxide as Electron Transport Interlayer with Large Stoichiometry Window

Highly efficient organic photovoltaic cells are demonstrated by incorporating low temperature solution processed indium zinc oxide (IZO) as cathode interlayers. The IZOs are synthesized using a combustion synthesis method, which enables low temperature processes (150–250 °C). We investigated the IZO films with different electron mobilities (1.4 × 10^–3 to 0.23 cm²/(V·s)), hydroxide–oxide content (38% to 47%), and surface roughness (0.19–5.16 nm) by modulating the ternary metal oxide stoichiometry. The photovoltaic performance was found to be relatively insensitive to the composition ratio of In:Zn over the range of 0.8:0.2 to 0.5:0.5 despite the differences in their electrical and surface properties, achieving high power conversion efficiencies of 6.61%–7.04%. Changes in composition ratio of IZO do not lead to obvious differences in energy levels, diode parameters and morphology of the photoactive layer, as revealed by ultraviolet photoelectron spectroscopy (UPS), dark current analysis and time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements, correlating well with the large IZO stoichiometry window that enables efficient photovoltaic devices. Our results demonstrate the robustness of this ETL system and provide a convenient approach to realize a wide range of multicomponent oxides and compatible with processing on flexible plastic substrates

Improving the Efficiency of Hematite Nanorods for Photoelectrochemical Water Splitting by Doping with Manganese

Here, we report a significant improvement of the photoelectrochemical (PEC) properties of hematite (α-Fe₂O₃) to oxidize water by doping with manganese. Hematite nanorods were grown on a fluorine-treated tin oxide (FTO) substrate by a hydrothermal method in the presence on Mn. Systematic physical analyses were performed to investigate the presence of Mn in the samples. Fe₂O₃ nanorods with 5 mol % Mn treatment showed a photocurrent density of 1.6 mA cm^–2 (75% higher than that of pristine Fe₂O₃) at 1.23 V versus RHE and a plateau photocurrent density of 3.2 mA cm^–2 at 1.8 V versus RHE in a 1 M NaOH electrolyte solution (pH 13.6). We attribute the increase in the photocurrent density, and thus in the oxygen evolving capacity, to the increased donor density resulting from Mn doping of the Fe₂O₃ nanorods, as confirmed by Mott–Schottky measurement, as well as the suppression of electron–hole recombination and enhancement in hole transport, as detected by chronoamperometry measurements