Dye-sensitized solar cells (DSSCs) emerged in the market as one of the most promising indoor photovoltaic technologies to address the need for wireless powering of low-consuming electronics and sensor nodes of the internet of things (IoT). The monolithic design structure of the cell (M-DSSCs) makes the devices simpler and cheaper, and it is straightforward for constructing in-series modules. The most efficient DSSCs reported so far are Co­(III/II)-mediated liquid junction cells with acetonitrile electrolytes; however, they are mostly unstable. This study reports on highly stable cobalt-mediated M-DSSCs, passing thermal cycling tests up to 85 °C according to ISOS standard protocols. Under 1000 h of aging in the dark and under simulated solar and artificial light soaking, all tested cells improved or retained their initial power conversion efficiency. Advanced long-term stability was achieved by eliminating the extrinsic factors of degradation, such as the interaction of the cell components with the environment and electrolyte leakage. This was obtained by encapsulation of the devices using a glass-frit sealant, including the holes for filling up the liquid components of the cells. The hermeticity of the encapsulation complies with the MIL-STD-883 standard fine helium gas leakage test, and its hermeticity remained unchanged after humidity–freeze cycles according to IEC 61646. The elimination of extrinsic degradation factors allowed reliable assessment of inner factors accountable for aging. The impact of the ISOS-protocol test conditions on the intrinsic device stability and long-term photovoltaic history of the M-DSSCs is discussed.

New route for fabrication of transparent conducting glasses for efficient photocurrent collection in large area DSSCs is demonstrated: current collectors were formed beneath the glass surface to achieve high cross-sectional area and good conductivity. The advantages of chromium metal for current collectors in DSSCs are presented. Polarization measurements revealed passivity of Cr in back electron recombination with electrolyte. Chromium was electrodeposited ca. 20 μm beneath glass surface into grooves in FTO-glass, which had been formed by photolithography assisted wet etching. Robust adhesion of Cr to glass up to 500 • C was achieved using interlayer of titanium, controllable formation of sponge-like microstructure of the metal and by designing wave-shape conducting lines. DSSCs photoanodes of 2.5 × 2.5 and 6.5 × 6.5 cm 2 were assembled on Cr-embedded FTO-glasses. The resulting DSSCs show power conversion efficiencies of 5.3% and 3.6% respectively for the 6.3 and 42.3 cm 2 devices; it outperforms the cells with blank FTO substrates, respectively 2.6 and 0.4% of efficiency, mainly due to the improvement of the filling factors. Significant decrease of series and electron transfer resistances in the photoanodes assembled on Cr-embedded FTO glasses was revealed. The cells with Cr current collectors maintained their efficiency during 3000 h under natural ageing.

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