Recent developments of perovskites oxides and spinel materials as platinum-free counter electrodes for dye-sensitized solar cells: A comprehensive review

Dye-sensitized solar cells (DSSC) are known as a hot subject in the photovoltaic (PV) field. Several materials are used to fabricate a DSSC, including titanium dioxide/metal oxide-based photoanodes, counter electrodes (CEs), dyes, and electrolytes. An efficient CE should be able to dramatically improve the photovoltaic performance, i.e., power conversion efficiency (PCE) and longstanding stability, in addition to decreasing total DSSC fabrication cost. Platinum (Pt) is commonly applied as CE of DSSCs but Pt is expensive and hence numerous studies have developed cheaper CE alternatives. Herein, a comprehensive review is presented on application of perovskites oxides and spinels utilized as CEs in DSSC devices. Examples of perovskite oxide materials used as CEs of DSSCs are (La0.8Sr0.2)0.98FeO3-delta/MWCNTs, 4% graphene-La2CdSnTiO4-WSe2, SrCo0.95P0.05O3-delta/MWCNTs, LaFeO2.965-delta Cl0.035-2-BM, 15%graphene-La2CuNiO6-ZnSe, (La0.8Sr0.2)0.95Ag0.05MnO3-delta/MWCNTs, La0.5Sr0.5-CoO3, La0.67Sr0.33MnO3, La0.65Sr0.35MnO3@8%reduced graphene oxide, La0.5Sr0.5CoO2.91@reduced graphene oxide, La0.7Sr0.3MnO3 nanoparticles/nitrogen-doped graphene, La0.7Ca0.3MnO3, 2-La0.9Ce0.1NiO3@f-MWCNT-ZnSe-CoSe2@CAB, 1:1 La2MoO6@MWCNT, LaNiO3/MWCNTs, SrRuO3-graphene quantum dots, Bi5FeTi3O15/ graphene-2, Bi4Ti3O12/graphene-3 so that the highest PCEs of 12.4, 12.23, 12.2, 11.4, and 11.00% are measured using the first five CEs. Examples of DSSC devices assembled with spinel cathode materials are FeNi3/ NiFe2O4@mGr, FeNi2S4/rGO, MnCo2O4@NiCo2O4/carbon paper (CP), CoNi2S4/RGO, ZnFe2O4/CNFs-Ti, CoFe2O4/graphene, NiCo2S4/CNFs, NiCo2S4 nanoflowers, NiCo2O4 nanoflower/nanosphere, NiCo2O4/carbon black, RGO-NiCo2S4, CuCo2S4, NiCo2S4, NiIn2S4, FeIn2S4, CoIn2S4, NiIn2S4, Co3S4, CoCr2S4/CNTs, MoIn2S4@CNT, and MgAl2O4 so that the highest PCEs of 12.14, 9.98, 9.58 +/- 0.06, 9.22, 9.05 +/- 0.05, 9.04, and 9 +/- 0.06% are measured using the first seven CEs. These results verify that fabrication of CEs using priceless perovskite oxides and spinels affords higher efficiencies and device stability for DSSCs compared to Pt-based devices.