Molecular Reaction Imaging of Single-Entity Photoelectrodes

Abstract

Photoelectrochemical cells have the potential to convert solar energy to liquid fuels. Nanostructured electrode materials are attractive light-harvesting materials for this purpose because their nanoscale dimensions minimize charge carrier transport distances to the solid/liquid interface. However, nanoscale materials are heterogeneous, and the influence of impurities, defects, and particle size/shape on the rates and efficiencies of the fundamental processes in photoelectrochemical cells is not entirely understood. This Perspective highlights molecular reaction imaging methods that spatially resolve principal processes in photoelectrochemical cells: (1) reaction intermediate imaging, (2) surface recombination imaging, and (3) charge transport imaging. We discuss opportunities to couple optical microscopy techniques with electron or X-ray microscopy characterization tools to reveal atomic-level structure–property relationships of single-nanoentity photoelectrodes. The atomistic detail of the semiconductor/electrolyte interface may guide the design and synthesis of nanostructured electrodes for direct solar fuels production.

Symmetry-Breaking Charge Separation in Molecular Constructs for Efficient Light Energy Conversion

“…Organic photovoltaics (OPVs) is a rapidly emerging renewable energy source, with a reported power conversion efficiency of ∼18% . The working principle of OPVs is similar to that of nature’s energy-conversion systems, wherein sunlight absorption, exciton formation, charge separation, and charge-carrier transport are the fundamental processes. , The availability of different color absorbing materials and their ability to make efficient, transparent photovoltaic devices have attracted the commercial solar device market . The efficiency of photovoltaics based on organic materials (OPV) is often limited by energetic and structural disorders. , Measured open-circuit voltage ( V oc ) of the organic solar cells is usually lower than those of inorganic solar cells.…”

“…26 The working principle of OPVs is similar to that of nature's energy-conversion systems, wherein sunlight absorption, exciton formation, charge separation, and charge-carrier transport are the fundamental processes. 27,28 The availability of different color absorbing materials and their ability to make efficient, transparent photovoltaic devices have attracted the commercial solar device market. 28 The efficiency of photovoltaics based on organic materials (OPV) is often limited by energetic and structural disorders.…”

Directly visualizing carrier transport and recombination at individual defects within 2D semiconductors

“…Clearly distinguishing the behavior of defects from that of the bulk material will require high-resolution imaging techniques capable of probing carrier transport and recombination, and a variety of experimental strategies along these lines have been demonstrated. Techniques such as scanning photocurrent microscopy, [22][23][24][25][26][27][28][29][30] scanning near-field optical microscopy, 31,32 electron beam induced current measurements, [33][34][35] or transient absorption microscopy [36][37][38][39][40] have been employed to generate valuable insights into the transport and recombination of carriers within 2DSCs. However, these experiments are often limited in terms of the complexity of the generated response or by the need for carriers to exhibit a strong spectroscopic signature.…”

Integrated Photovoltaic Charging and Energy Storage Systems: Mechanism, Optimization, and Future

“…For solar redox batteries, nanostructured materials can provide a large interface area between the photoelectrodes and the electrolyte, which is conducive to the transport and separation of charge carriers. [104][105][106] Based on the strategy of optimizing the TiO 2 nanostructure, Li et al facilitated light absorption through the prepared nanostructured TiO 2 , thereby enhancing the charge collection efficiency (Figure 7a). [24] At the same time, the photoelectrode with iodide ion redox shuttle was introduced into the LIB, and the charging voltage of the LiFePO 4 cathode was reduced to 2.78 V, and the charging voltage drop was equivalent to about 20% energy saving (Figure 7b).…”