Global energy and environmental crises are among the most pressing challenges facing humankind. To overcome these challenges, recent years have seen an upsurge of interest in the development and production of renewable chemical fuels as alternatives to the nonrenewable and high-polluting fossil fuels. Photocatalysis, photoelectrocatalysis, and electrocatalysis provide promising avenues for sustainable energy conversion. Single-and dual-component catalytic systems based on nanomaterials have been intensively studied for decades, but their intrinsic weaknesses hamper their practical applications. Multicomponent nanomaterial-based systems, consisting of three or more components with at least one component in the nanoscale, have recently emerged. The multiple components are integrated together to create synergistic effects and hence overcome the limitation for outperformance. Such higher-efficiency systems based on nanomaterials will potentially bring an additional benefit in balance-of-system costs if they exclude the use of noble metals, considering the expense and sustainability. It is therefore timely to review the research in this field, providing guidance in the development of noble-metal-free multicomponent nanointegration for sustainable energy conversion. In this work, we first recall the fundamentals of catalysis by nanomaterials, multicomponent nanointegration, and reactor configuration for water splitting, CO 2 reduction, and N 2 reduction. We then systematically review and discuss recent advances in multicomponent-based photocatalytic, photoelectrochemical, and electrochemical systems based on nanomaterials. On the basis of these systems, we further laterally evaluate different multicomponent integration strategies and highlight their impacts on catalytic activity, performance stability, and product selectivity. Finally, we provide conclusions and future prospects for multicomponent nanointegration. This work offers comprehensive insights into the development of cost-competitive multicomponent nanomaterial-based systems for sustainable energy-conversion technologies and assists researchers working toward addressing the global challenges in energy and the environment.

Following recent developments in photoelectrochemical and photovoltaic–electrosynthetic systems, we present the benefits of III–V semiconductors for solar water splitting. In addition to their interesting light absorption and carrier transport properties, III–V alloys and multijunction structures enable the highest solar-to-hydrogen conversion efficiencies. However, many obstacles still stand in the way of practical realization of III–V solar water-splitting systems. Various surface protection strategies are being developed to address the instability of III–V semiconductors in an electrolyte. Meanwhile, multiple cost-reduction approaches are being implemented, including the use of solar concentration, epitaxial lift-off or spalling for substrate reuse, and monolithic or heterogeneous integration on silicon substrates. All these advances make III–V photoabsorbers a promising route toward decarbonated hydrogen production and pave the way to long-term deployment in real-world applications.

Technological platforms offering efficient integration of III-V semiconductor lasers with silicon electronics are eagerly awaited by industry. The availability of optoelectronic circuits combining III-V light sources with Si-based photonic and electronic components in a single chip will enable, in particular, the development of ultra-compact spectroscopic systems for mass scale applications. The first circuits of such type were fabricated using heterogeneous integration of semiconductor lasers by bonding the III-V chips onto silicon substrates. Direct epitaxial growth of interband III-V laser diodes on silicon substrates has also been reported, whereas intersubband emitters grown on Si have not yet been demonstrated. We report the first quantum cascade lasers (QCLs) directly grown on a silicon substrate. These InAs/AlSb QCLs grown on Si exhibit high performances, comparable with those of the devices fabricated on their native InAs substrate. The lasers emit near 11 µm, the longest emission wavelength of any laser integrated on Si. Given the wavelength range reachable with InAs/AlSb QCLs, these results open the way to the development of a wide variety of integrated sensors.

In recent years, carrier-selective contacts have emerged as an efficient alternative to the conventional doped p–n or p–i–n homojunction for charge carrier separation in high-performance solar cells. However, so far, there has been no development in carrier-selective contacts for GaAs solar cells. This paper proposes an alternative device structure and reports an 18.5% efficient single-junction GaAs solar cell using zinc oxide (ZnO) as an electron-selective contact. A detailed X-ray and ultraviolet photoelectron spectroscopy depth profile analysis is performed to reveal the mechanism of carrier selectivity and improved efficiency compared to homojunction cells grown under similar conditions. Moreover, a detailed loss analysis shows that the fabricated solar cell has the potential to reach more than 25% efficiency with further optimization. The device structure proposed in this paper will provide a route to reduce the complexity and cost of epitaxially grown cells while also allowing for the possibility to fabricate high-efficiency III–V solar cells using low-cost growth techniques (such as closed-space vapor transport and thin-film vapor–liquid–solid) where doping can be extremely challenging.