| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
N2, GaAs Nanopillar Photovoltaics Based on Catalyst-Free Patterned Growth |
| Author(s) |
Giacomo Mariani, Ping-Show Wong, Joshua Shapiro, Diana L. Huffaker |
| On-Site Speaker (Planned) |
Giacomo Mariani |
| Abstract Scope |
In this work, we present nanostructured core-shell solar cells based on patterned GaAs nanopillars grown by MOCVD.1 The patterns are photolithographically defined and center-to-center pitch, hole size and mask arrangement can be precisely pre-determined at nanometric resolution. Our inherently catalyst-free growth mode eliminates any metal (i.e. Au) diffusion into the nanopillars that could hinder the electron-hole pair extraction, paramount in photovoltaics. The lattice-matched growth capability also avoids threading dislocations that normally act as recombination centers, worsening the leakage current in pn-junction based devices. The study aims at evaluating different contact workfunctions for the transparent top electrode applied to GaAs nanopillar photovoltaic devices. Electronic transport along the photo-junction and carrier extraction can be hugely hindered by a non-purely ohmic contact, resulting in low power conversion efficiencies. Aluminum-doped Zinc Oxide (AZO)2 and Indium-doped Tin Oxide (ITO) are chosen as front electrodes. Comparisons are made in terms of photocurrent density-voltage (J-V) characteristics (under dark and standard AM 1.5 conditions) and external quantum efficiency (EQE), both standard figures of merit in the photovoltaic field. Devices with ITO as top contact are measured along with devices with AZO as front electrode. The best device with AZO as top contact exhibits an open circuit voltage (VOC) of 0.2V, short circuit current density (JSC) of 6.6 mA/cm2 and a fill factor (FF) of 37% whereas the best device with ITO as top electrode showed a VOC=0.39V, JSC=17.8 mA/cm2 and a fill factor FF above 34% with a power conversion efficiency of 2.54% , the highest achieved to date in GaAs nanowire photovoltaics. The main figures of merit (J-V characteristics, external quantum efficiencies) are presented in a final comparative study. |
| Proceedings Inclusion? |
Undecided |