Photoelectrochemical and spectrophotometric studies on dye-sensitized solar cells (DSCs) and stable modules (DSCMs) based on natural apocarotenoids pigments

We present a study on dye-sensitized solar cells (DSCs) and we fabricate dye-sensitized solar modules (DSCMs) based on natural apocarotenoids extracted from the achiote's seeds (annatto). Use of less polar solvent such as diethyl ether improves the bixin concentration in the annatto extract which, was employed as sensitizer in the devices. We measure IPCE max (∼33%) and estimate ϕinj ≥ 0.438 for annatto. By accurate and progressive optimization of both TiO2 multilayer photoanode and of electrolyte composition an efficiency (η) around 1.6%, is achieved, with an improvement of about ∼742% compare to the best performance for annatto extract, so far reported. DSCM shows stability which overcomes 1000 h (shelf-life test), under 1 sun, and produces a battery capacity of ∼46.8 Ah, the equivalent to ∼15 type AAA standard battery, in a similar time period. Although annatto based DSCMs are still below the efficiency requirements for practical applications for large scale industry, our encouraging results, testify the potentiality of this pigment in the production of non-toxic, cheap, long term stable and environmentally friendly vegetable based solar devices, as alternatives to batteries for small electronic goods market.