Knowledge Bank

This research addresses the need to develop flexible organic tunneling junction candidates for multi-junction solar cells by evaluating staggered bandgap junction candidates using new hybrid organic tunnel junctions that juxtapose thin, bendable metal oxide layers. Multi-junction Solar Cells use multiple PN junction diodes in order to absorb light more efficiently than traditional solar cells. However, when each of the multiple PN junctions in the solar cells absorbs different portions of the sun’s spectrum, parasitic resistances are formed between these junctions due to polarity mismatches. This work was prompted by prior research by Prof. Berger’s group at OSU that demonstrated the feasibility of fabricating organic, polymer-based tunneling diodes using thin TiO2 with MEH-PPV polymer. Berger’s diodes have the potential to form flexible tunneling junctions for low-power negative differential resistance(NDR) based circuits. This project extends that technology to multi-junction organic solar cells and offers a flexible form factor with lower costs than their inorganic alternatives, such as silicon. The focus is to further improve performance and streamline the fabrication process of the tunneling diodes convolved with solar cell fabrication above and below it. After fabrication of tunneling diodes, using reactive sputtering to deposit metal oxides and evaporation or spin coating to deposit organic materials, IV testing is used to evaluate completed diodes. Preliminary results show that diodes fabricated using MoO3 films with organic phthalocyanine(CuPc) indicate Zener reverse tunneling behavior, meaning that these materials are potential candidates for stacked, organic tandem solar cells. The potential benefits of this research are more efficient tunneling junctions for flexible, organic, multi-junction solar cells, which offer lower costs while improving portability and ruggedness as compared to their inorganic alternatives. The broader implications are to introduce flexible, organic solar cells that can be incorporated easily into electric automobiles, backpacks, coats, etc. as an alternative point-of-use energy source.