Towards single nanowire solar cell based on novel radial p-n junction

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.advisor Dhaka, Veer Khayrudinov, Vladislav 2017-05-11T10:30:55Z 2017-05-11T10:30:55Z 2017-05-08
dc.description.abstract One of the most promising applications, the 1D semiconductor nanowires (NWs) offer, is the development of next generation solar cells at low-cost and higher efficiency. Group III–V semiconductor NWs, especially GaAs and InP, are the ideal semiconductor materials to build such devices on low-cost platforms. The aim of this work was to fabricate and study the fundamental working mechanisms of single nanowire solar cell and photodetector based on novel radial p-n junction in a core-shell geometry. The Au-assisted GaAs NWs were grown and doped in situ using metalorganic vapour phase epitaxy (MOVPE). In this study, a unique lithography-free technique was employed on an ensemble of NWs to isolate the core (p-type) from the shell (n-type) on the growth substrate. Electron beam lithography (EBL) was used to make metal contacts to the single core-shell NWs. In that respect, specific contact schemes were developed to realize ohmic contacts between the metal electrodes and the NWs. Electrical measurements of single nanowire device revealed perfect I-V behaviour confirming the formation of radial p-n junction diode. For characterization of NWs, scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and photocurrent spectroscopies were employed. Furthermore, surface passivation of NWs was identified as one of the key issues in functioning of the photovoltaic device as no photo response was detected without the same. The surface passivation of GaAs NWs with higher band gap AlGaAs layers resulted in dramatic enhancement of the PL intensity, and the photocurrent measurements of the device revealed a broad photo response in the visible spectrum range of the light, indicating a successful working of a single nanowire as a photodetector. However, although a functioning radial p-n junction was demonstrated, no solar response was detected from the single nanowire structure because of yet many unaddressed challenges such as high contact resistance, doping optimisation, absence of intrinsic region and unoptimised geometry. In summary, a single nanowire based photodetector was successfully demonstrated, and a full fabrication process was studied and developed for making progress towards realising the functional single nanowire based radial p-n junction solar cells in the future. en
dc.format.extent 94+7
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.title Towards single nanowire solar cell based on novel radial p-n junction en
dc.type G2 Pro gradu, diplomityö fi Sähkötekniikan korkeakoulu fi
dc.subject.keyword nanowire en
dc.subject.keyword metalorganic vapour phase epitaxy en
dc.subject.keyword photodetector en
dc.subject.keyword solar cell en
dc.subject.keyword core-shell en
dc.subject.keyword p-n junction en
dc.identifier.urn URN:NBN:fi:aalto-201705114615
dc.programme.major Micro- and Nanosciences en
dc.programme.mcode ELEC3037 en
dc.type.ontasot Master's thesis en
dc.type.ontasot Diplomityö fi
dc.contributor.supervisor Lipsanen, Harri
dc.programme NanoRad - Master’s Programme in Nano and Radio Sciences (TS2013) en
dc.ethesisid Aalto 9319
dc.location P1 fi

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