Nano-patterning of inorganic materials for photovoltaic applications

In this work, the pattern replication in non-wetting templates (PRINT) technique has been utilized for the patterning of inorganic materials including metal oxides and quantum dots for hybrid inorganic-organic solar cells. The PRINT technique is an attractive method for solar cell production because of its compatibility with a wide range of organic and inorganic reagents relevant to BHJ fabrication, amenability for scale-up, and application to large area device fabrication. The PRINT process was used to pattern inorganic oxides, including titania, on a sub-500 nm length scale. The inherent flexibility of this methodology was demonstrated by generating patterns on a variety of substrates, with aspect ratios greater than 1, with a second layer of features on top of an initial layer without pattern destruction, and with sub-100 nm sized features for photovoltaics applications. This technique was applied to hybrid solar cell technology by fabricating solar cells with these sub-100 nm titania features. The patterned titania/polymer devices showed a two-fold improvement in power conversion efficiency (PCE) when compared to flat titania/polymer devices. Furthermore, CdSe quantum dots (QDs) were synthesized and then used for patterning. The inert nature of the PFPE molds was demonstrated through the patterning of QDs with different surface ligands in a variety of solvents. Nanometer-scale diffraction gratings have been successfully replicated with CdSe QDs and subsequently coated with a conjugated polymer film for PV device fabrication. Finally, the PRINT technique has also been extended to fabrication schemes for different optical applications. An ordered template for surface-enhanced Raman spectroscopy (SERS) was fabricated with 120 nm wide holes that allowed for the formation of Ag nanoparticle dimers using a meniscus force deposition method. These dimers provided hotspots where an enhanced Raman signal was observed. Additionally, in effort to fabricate a superlens capable of directly imaging subwavelength structures, a simple metamaterial diffraction grating device was generated by replicating a blazed diffraction grating in PMMA on top of alternating metal dielectric layers. In this device, the amplification and conversion of evanescent waves into propagating ones was demonstrated