Effect of Spinel Inversion on (Co_xFe_1−x)₃O₄ All‐Oxide Solar Cell Performance

Abstract

Oxide materials have been widely investigated for use as absorber layers in high‐performance solar cells, and in this study combinatorial methods were used to specifically investigate cobalt–iron (Co–Fe) oxide composites. Structural inversion of Co–Fe oxides from a normal to an inverse spinel structure occurs at the critical composition of approximately 33 % Fe added to Co, causing changes in the crystallinity, symmetry, sub‐lattice vibrational modes, optical bandgap, and electrical resistivity. When used as an absorber layer in all‐oxide solar cells with the multi‐layered geometry of glass|FTO|TiO2|Co–Fe–O|Au, enhanced photovoltaic performance was observed, with a maximum Voc of 534 mV at a composition of approximately 45 % Fe and a 200 % improvement in Pmax compared to cobalt‐rich devices. Using combinatorial data maps of the various material properties, a significant correlation between the solar cell properties and the chemical composition of the Co–Fe–O layer was revealed. This correlation allows for a better understanding of the Co–Fe–O system, which is a necessary step towards the development of Co–Fe–O‐based all‐oxide solar cells.

FIB plan view lift-out sample preparation for TEM characterization of periodic nanostructures obtained by spinodal decomposition in Co1.7Fe1.3O4 thin films

“…The compositions close to Co 1. 3 are also visible from the 300 nm linear analysis shown in Figure 4d, but cannot be exactly defined at lower scale (i.e. within the column diameter).…”

“…The average Co 1.8 Fe 1.2 O 4 composition deduced from the total spectrum (Figure 6a) is close to the nominal Co 1.7 Fe 1. 3…”

“…The iron -cobaltites spinel Co 3x Fe 3-3x O 4 (x ≥ 0.5) have not so far been as widely used in the industry as other spinels such as ferrites in particular. Their properties, however, are of interest for certain technological applications, among which can be mentioned the electrodes for batteries and supercapacitors [1,2], the absorber layers in high-performance solar cells [3], the magnetic logic cells [4] and the microwave components [5]. The formation of periodic organizations at a nanoscale by spinodal decomposition within the miscibility gap of the CoFe 2 O 4 -Co 3 O 4 phase diagram also makes it possible to imagine their use in magnetoresistance components.…”

Functional Oxides for Photoneuromorphic Engineering: Toward a Solar Brain

“…absorber (with TiO 2 as the n-type window layer) resulted in a low PCE of 10 -2 -10 -3 % [282] , [283] . Dopants such as Li, Cu and Fe into the spinel Co 3 O 4 layer has been reported resulting in much enhanced p-type conductivity [284] , [285] , [286] . Patel et al [287] reported that a rapid interfacial layer has a beneficial effect onto the V oc in TiO 2 /Co 3 O 4 /MoO 3 all-oxide solar cells [288] .…”

Rapid Thermal Treatment of Reactive Sputtering Grown Nanocrystalline Co3 O4 for Enhanced All-Oxide Photovoltaics

“…This was enhanced by 0.6 V by inserting a MoO 3 hole selective layer . Enhanced V OC was also obtained when Co 3 O 4 was doped by Li or Fe . Studies on back metal contacts of Ag, Cu, Ni, and Co for Co 3 O 4 photovoltaics have shown a consistent V OC of 0.4 V .…”