Broad Band Light Absorption and High Photocurrent of (In,Ga)N Nanowire Photoanodes Resulting from a Radial Stark Effect

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• 作者：Jumpei KamimuraPeter Bogdanoff ; Pierre Corfdir ; Oliver Brandt ; Henning Riechert ; Lutz Geelhaar
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：December 21, 2016
• 年：2016
• 卷：8
• 期：50
• 页码：34490-34496
• 全文大小：413K
• ISSN：1944-8252

文摘

The photoelectrochemical properties of (In,Ga)N nanowire photoanodes are investigated using H₂O₂ as a hole scavenger to prevent photocorrosion. Under simulated solar illumination, In_0.16Ga_0.84N nanowires grown by plasma-assisted molecular beam epitaxy show a high photocurrent of 2.7 mA/cm² at 1.2 V vs reversible hydrogen electrode. This value is almost the theoretical maximum expected from the corresponding band gap (2.8 eV) for homogeneous bulk material without taking into account surface effects. These nanowires exhibit a higher incident photon-to-current conversion efficiency over a broader wavelength range and a higher photocurrent than a compact layer with higher In content of 28%. These results are explained by the combination of built-in electric fields at the nanowire sidewall surfaces and compositional fluctuations in (In,Ga)N, which gives rise to a radial Stark effect. This effect enables spatially indirect transitions at energies much lower than the band gap. The resulting broad band light absorption leads to high photocurrents. This benefit of the radial Stark effect in (In,Ga)N nanowires for solar harvesting applications opens up the perspective to break the theoretical limit for photocurrents.