Opportunities from Doping of Non‐Critical Metal Oxides in Last Generation Light‐Conversion Devices

Abstract

The need to develop sustainable energy solutions is an urgent requirement for society, with the additional requirement to limit dependence on critical raw materials, within a virtuous circular economy model. In this framework, it is essential to identify new avenues for light‐conversion into clean energy and fuels exploiting largely available materials and green production methods. Metal oxide semiconductors (MOSs) emerge among other species for their remarkable environmental stability, chemical tunability, and optoelectronic properties. MOSs are often key constituents in next generation energy devices, mainly in the role of charge selective layers. Their use as light harvesters is hitherto rather limited, but progressively emerging. One of the key strategies to boost their properties involves doping, that can improve charge mobility, light absorption and tune band structures to maximize charge separation at heterojunctions. In this review, effective methods to dope MOSs and to exploit the derived benefits in relation to performance enhancement in different types of devices are identified and critically compared. The work is focused specifically on the best opportunities coming from the use of non‐critical raw materials, so as to contribute in defining an economically feasible roadmap for light conversion technologies based on these highly stable and widely available compounds.

Control of electronic band profiles through depletion layer engineering in core–shell nanocrystals

“…Doped metal oxide (MO) nanocrystals (NCs) are gaining the attention of the scientific community thanks to their unique properties, such as high electron mobility 1 , the tuneability of their carrier density over several orders of magnitude 2 , chemical stability 3 , and low toxicity 3 , as well as suitable operating temperature 1 , which makes them appropriate for a large plethora of applications, ranging from nanoelectronics and plasmonics to the next-generation energy storage 3 – 11 . In doped MO NCs, surface states, such as surface trap states, defects, vacancies, as well as surface ligands and other bound molecules induce Fermi level pinning causing an upward bending of the energetic bands 2 , 4 , 12 – 18 .…”

Multi-charge transfer from photodoped ITO nanocrystals

“…Metal oxide (MO) semiconductors are inorganic materials of great interest in the field of optoelectronic applications for energy-related technology. 1 They offer an ideal combination of several properties ranging from environmental stability, chemical tunability 2 to optical transparency and good charge mobility. 3 The ability to modulate their charge carrier density through aliovalent substitutional doping and post-synthesis methods boosts the implementation of doped MO nanocrystals (NCs), such as Sn-doped In 2 O 3 (Indium Tin Oxide [ITO]) NCs.…”

Transparent Photovoltaics for Self-Powered Bioelectronics and Neuromorphic Applications

“…However, considering biocompatibility and the nontoxic nature, future research will be mainly restricted to materials with biocompatibility with the human body. 35 Metal-oxide-based memory devices are also capable of exhibiting sensory behavior such as photoreception 8 and nociception 51 as is explicitly elaborated by Kim et al, 51 who fabricated transparent artificial photonic nociceptors (see Figure 4b). The indispensable feature of both neuromorphic devices is the self-powered nature of TPV devices.…”

“…On a practical level, solid-state materials such as oxides and two-dimensional (2D) materials can be preferred for their neuromorphic functionality. These materials offer inborn doping capabilities, heterostructure configurations, ionic conductivity, bandgap engineering, wafer-scale fabrication, stability, and integration with existing platforms. − …”

“…This suggests that oxide-based TPVs may be highly suitable for achieving non-von Neumann systems that could emulate biological synaptic and neural features. However, considering biocompatibility and the nontoxic nature, future research will be mainly restricted to materials with biocompatibility with the human body …”