Exciton generation, dissociation, free carrier transport, and charge extraction play an important role in the short-circuit current (J sc) and power conversion efficiency of an organic bulk heterojunction (BHJ) solar cell (SC). Here we study the impact of band offset at the interfacial layer and the morphology of active layer on the extraction of free carriers. The effects are evaluated on an inverted BHJ SC using zinc oxide (ZnO) as a buffer layer, prepared via two different methods: ZnO nanoparticle dispersed in mixed solvents (ZnO A) and sol–gel method (ZnO B). The device with ZnO A buffer layer improves the charge extraction and J sc. The improvement is due to the better band offset and morphology of the blend near the ZnO A/active layer interface. Further, the numerical analysis of current–voltage characteristics illustrates that the morphology at the ZnO A/active layer interface has a more dominant role in improving the performance of the organic photovoltaic than the band offset.

This work presents a photochemical and thermal treatment strategy to prepare in situ gold–platinum bimetallic nanoparticle-loaded titania photocatalysts with self-doped Ti3+ states (Au–Pt/Ti3+ nc-TiO2). In situ loading of Au–Pt bimetallic nanoparticles and Ti3+ self-doping in the TiO2 crystal lattice result in excellent solar light photocatalytic activity. The Au–Pt/Ti3+ nc-TiO2 displays an improved hydrogen evolution rate (98.53 mmol h–1 g–1) when compared to in situ gold-loaded and in situ platinum-loaded titania (Au/Ti3+ nc-TiO2 and Pt/Ti3+ nc-TiO2, respectively) photocatalysts. The Au–Pt/Ti3+ nc-TiO2 photocatalyst is further restructured into titania inverse opal (Au–Pt/Ti3+ io-TiO2) photocatalyst by a facile colloidal photonic crystal (CPC) infiltration method. The Au–Pt/Ti3+ io-TiO2 photocatalyst displays a superior solar hydrogen evolution profile (181.77 mmol h–1 g–1) compared to all the other photocatalysts investigated for hydrogen production experiments, which makes them potential candidates for solar water splitting.

The light soaking phenomenon, in chlorine-based mixed halide perovskite solar cells (PSC) with p-i-n configuration, is studied. Due to light soaking, the solar cells have shown improved open circuit voltage, fill factor (FF), and power conversion efficiency without much change in short circuit current. The devices have returned to their original state upon extended exposure to dark conditions. Capacitance spectroscopy is used to understand the effect of light soaking on various photovoltaic parameters. The observed increase of capacitance value with light soaking in the low frequency region of the capacitance-frequency (C-F) plot is elucidated, as the coupled effect of electronic and ionic processes involving defects. The decrement in the mid-frequency capacitance is attributed to an increase in the width of the depletion region which eventually facilitated the improvement in open circuit voltage and FF. Defect densities, and its distribution in the energy space, are deduced before and after light soaking. The defects density of states of PSC studied are found to reduce from 10 16 to 10 15 eV −1 cm −3 , with a Gaussian distribution, and having a peak energy shift from 0.27 to 0.26 eV.

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