Recent studies in monocrystalline semiconductor solar cells are focused on mechanically stacking multiple cells from different materials to increase the power conversion efficiency. Although, the results show promising increase in the device performance, the cost remains as the main drawback. In this study, we calculated the theoretical limits of multistacked 1D and 2D microstructered inorganic monocrstalline solar cells. This system is studied for Si and Ge material pair. The results show promising improvements in the surface reflection due to enhanced light trapping caused by photon-microstructures interactions. The theoretical results are also supported with surface reflection and angular dependent power conversion efficiency measurements of 2D axial microwall solar cells. We address the challenge of cost reduction by proposing to use our recently reported mass-manufacturable fracture-transfer- printing method which enables the use of a monocrystalline substrate wafer for repeated fabrication of devices by consuming only few microns of materials in each layer of devices. We calculated thickness dependent power conversion efficiencies of multistacked Si/Ge microstructured solar cells and found the power conversion efficiency to saturate at 26% with a combined device thickness of 30 μm. Besides having benefits of fabricating low-cost, light weight, flexible, semi-transparent, and highly efficient devices, the proposed fabrication method is applicable for other III-V materials and compounds to further increase the power conversion efficiency above 35% range.
Employing DNA molecules provide opportunities for electronics and photonics applications, serving to enhance the
device properties as active part of the device or being a linker agent to aid in the self assembly of nanostructures. In this
work, the effects of two different sets of biological materials, stand alone DNA sequences and Pt-DNA nanowires on the
device properties of bulk heterojunction solar cell devices are being investigated. During the metallization of DNA, a Pt
ion activation process over the DNA backbone is followed by a reduction process, where positively charged Pt
nanoparticles are assembled on the DNA sequences to form the Pt-DNA complexes via sequential ionic reduction. Pt
nanowires 20 nm in diameter are obtained by optimization of the salt reduction parameters of this. Several solar cell
devices consisting of Al/P3HT:PCBM/PEDOT:PSS/ITO layers, are fabricated where DNA sequences or the Pt-DNA
nanostructures are placed in between the P3HT:PCBM and the PEDOT:PSS layers. Both DNA sequences and Pt-DNA
nanostructures are spray coated onto the PEDOT:PSS layer before spin-coating the PEDOT:PSS polymer mixture. The
effects of the DNA and Pt-DNA nanostructures are observed from the I-V characteristics under the standard AM1.5G 1
Sun Test Condition. We observe that both DNA sequences and Pt-DNA nanostructures improve the power conversion
efficiency (PCE) by %12 and %25 respectively. We believe that this increase in PCE is provided by the enhancement of
hole collection and a reduction of the recombination loses. In addition, improvement in the short circuit current (Isc) is
observed for the DNA containing network. Similar improvements in both Isc and the open circuit voltage (Voc) are
observed for the Pt-DNA containing network. We hypothesize that while the high resistance of the DNA network limits
charge collection, comparably low resistance Pt-DNA network improves this feature.
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