Single atom catalysts (SACs) are promising electrocatalysts for CO2 reduction reaction (CO2RR), in which the coordination environment plays a crucial role in intrinsic catalytic activity. Taking the regular Fe porphyrin (Fe‐N4 porphyrin) as a probe, the study reveals that the introduction of opposable S atoms into N coordination (Fe‐N2S2 porphyrin) allows for an appropriate electronic structural optimization on active sites. Owing to the additional orbitals around the Fermi level and the abundant Fe dz2 orbital occupation after S substitution, N, S cocoordination can effectively tune SACs and thus facilitating protonation of intermediates during CO2RR. CO2RR mechanisms lead to possible C1 products via two‐, six‐, and eight‐electron pathways are systematically elucidated on Fe‐N4 porphyrin and Fe‐N2S2 porphyrin. Fe‐N4 porphyrin yields the most favorable product of HCOOH with a limiting potential of −0.70 V. Fe‐N2S2 porphyrin exhibits low limiting potentials of −0.38 and −0.40 V for HCOOH and CH3OH, respectively, surpassing those of most Cu‐based catalysts and SACs. Hence, the N, S cocoordination might provide better catalytic environment than regular N coordination for SACs in CO2RR. This work demonstrates Fe‐N2S2 porphyrin as a high‐performance CO2RR catalyst, and highlights N, S cocoordination regulation as an effective approach to fine tune high atomically dispersed electrocatalysts.

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The influence of junction depth in III-V cell structures was investigated for GaAs and InGaP cells. Typical cells of this type employ a shallow junction design. We have shown that for both materials investigated a deep junction close to the back of the cell performs better than a shallow junction cell. The deep junction cells operate in the radiative recombination regime, whereas in the shallow junction cells non-radiative recombination is dominant. The steeper slope of the IV curve boosts the fill-factor by 3-4%, which is thereby the most improved cell parameter. In order to minimize collection losses in the upper part of the cell, the optimal active layer thickness of the GaAs deep junction cell is only two-thirds of a shallow junction cell. The associated lower cell current is however more than compensated by the higher fill-factor. The best deep junction GaAs cell shows a record efficiency of 26.5% for a GaAs cell on substrate. In the thinner InGaP deep junction cell the current loss does not occur, leading to 1.6% higher efficiency than for the shallow junction cell.

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