NiFeOx decorated Ge-hematite/perovskite for an efficient water splitting system.

To boost the photoelectrochemical water oxidation performance of hematite photoanodes, high temperature annealing has been widely applied to enhance crystallinity, to improve the interface between the hematite-substrate interface, and to introduce tin-dopants from the substrate. However, when using additional dopants, the interaction between the unintentional tin and intentional dopant is poorly understood. Here, using germanium, we investigate how tin diffusion affects overall photoelectrochemical performance in germanium:tin co-doped systems. After revealing that germanium is a better dopant than tin, we develop a facile germanium-doping method which suppresses tin diffusion from the fluorine doped tin oxide substrate, significantly improving hematite performance. The NiFeOx@Ge-PH photoanode shows a photocurrent density of 4.6 mA cm-2 at 1.23 VRHE with a low turn-on voltage. After combining with a perovskite solar cell, our tandem system achieves 4.8% solar-to-hydrogen conversion efficiency (3.9 mA cm-2 in NiFeOx@Ge-PH/perovskite solar water splitting system). Our work provides important insights on a promising diagnostic tool for future co-doping system design.

Perovskite precursor solution chemistry: from fundamentals to photovoltaic applications.

Over the last several years, inorganic-organic hybrid perovskites have shown dramatic achievements in photovoltaic performance and device stability. Despite the significant progress in photovoltaic application, an in-depth understanding of the fundamentals of precursor solution chemistry is still lacking. In this review, the fundamental background knowledge of nucleation and crystal growth processes in solution including the LaMer model and Ostwald ripening process is described. This review article also highlights the recent progress in precursor-coordinating molecule interaction in solution along with the role of anti-solvent in the solvent engineering process to control nucleation and crystal growth. Moreover, chemical pathways from precursor solution to perovskite film formation are given. This represents identification of the intermediate phase induced by precursor-coordinating molecule interaction and responsible intermediate species for uniform and dense perovskite film formation. Further to the description of chemical phenomena in solution, the contemporary progress in chemical precursor composition is also provided to comprehend the current research approaches to further enhance photovoltaic performance and device stability. On the basis of the critical and comprehensive review, we provide some perspectives to further achieve high-performance perovskite solar cells with long-term device stability through precisely controlled nucleation and crystal growth in precursor solution.