1. 2 New Materials and Concepts for Cells and Modules
Summary / Abstract:
Photovoltaics (PV), based on organic, inorganic or perovskite absorbers, can be fabricated as lightweight and flexible modules, making them attractive for integration in building façades and consumer products. These PV technologies rely on substrates coated with a transparent electrode of high transparency and low sheet resistance. ITO (indium-tin-oxide) is by far the most common electrode, despite its high cost, poor mechanical stability and low figure-of-merit when applied on flexible substrates like polyethylene terephthalate (PET). In this investigation, we have developed an alternative to ITO-coated PET, based on dielectric/metal/dielectric (DMD) multilayers, sputtered at rates compatible to high-throughput, industrial production. As dielectrics, compounds based on MoOx and TiOx, were used, with electronic properties that allow their use either as anodes or as cathodes in different solar cell architectures. Optimized DMD electrodes offer: (i) better performance/cost figure than ITO-on-PET, (ii) sheet resistance <10 Ω/sq, without substrate heating during deposition, (iii) unsurpassed stability of the resistance against bending and (iv) adaptability to specific device energetics. The industrial applicability of the DMD electrodes was demonstrated by their deposition in a fast, roll-to-roll process and by their implementation for the fabrication of perovskite solar cells, with performance larger than the one achieved for ITO-coated substrates. The proof-of-concept of continuous manufacturing and the functional validation of the DMD coated polymer substrates opens the doors for industrial applications of flexible PV devices, as well as other optoelectronic applications.