Development and characterization of photovoltaic tandem-junction nanowires using electron-beam-induced current measurements

Vertically Processed GaInP/InP Tandem-Junction Nanowire Solar Cells

“…As seen from Figure b,c, a positive EBIC current is observed when the electron beam illuminates either of the subcells, while a negative current is measured at the position of the Esaki tunnel junction under the applied forward bias conditions due to the opposite direction of the junction. These observations are in agreement with previously reported results and confirm that the doping profile of the tandem-junction photovoltaic NWs is as intended.…”

“…To investigate whether the functional structure on the NWsincluding two n–i–p subcells connected by an Esaki tunnel diodeworks as intended, we performed EBIC measurements. EBIC has previously been shown to be a valuable tool for the development and characterization of photovoltaic NWs. ,, It is used to verify the doping profile and junction locations and, in combination with I – V measurements, study the electrical properties of the NW, including V OC addition and the current output under illumination with the electron beam. ,, Figure shows the results of EBIC measurements of an NW on a representative sample; further measurements are shown in Figure S4. As seen from Figure b,c, a positive EBIC current is observed when the electron beam illuminates either of the subcells, while a negative current is measured at the position of the Esaki tunnel junction under the applied forward bias conditions due to the opposite direction of the junction.…”

“…The NWs consist of 3 functional parts: an InP bottom cell, an Esaki tunnel junction, and a Ga x In 1−x P top cell. The Esaki tunnel diode was realized using a GaInP p + and an InP n + segment, 23 cally in Figure 1. Please note that the InP bottom cell and Esaki tunnel junction are identical across all presented samples, including the composition of the GaInP p + segment, forming a part of the Esaki tunnel diode.…”

“…In particular, the reduced susceptibility to radiation damage observed for NW structures in theoretical as well as experimental studies is only relevant as long as all the active components are located within the NW. , Given that photovoltaic devices for space are an important scenario of application for III–V NW array devices, this motivates the development of NW multijunction photovoltaics with multiple p–n junctions located within a NW. Previous work in our group has established parameters for the growth of axially defined GaInP/InP double-junction as well as GaInP/InP/InAsP triple-junction photovoltaic NWs, which were grown in arrays but evaluated as single NWs. , Please note that these combinations of materials would not be possible using planar layers but are enabled by radial strain relaxation via the free surface of the NWs. , In this paper, we report on the processing of GaInP/InP tandem-junction NW arrays into fully functional photovoltaic devices, contacting approximately 3 million NWs in parallel on each 800 × 800 μm 2 -sized device. By changing the Ga x In 1– x P composition x between samples, we aim to understand the influence of the top cell composition on device performance.…”

A cathodoluminescence study of InP/InGaP axially heterostructured NWs for tandem solar cells

“…The results are interpreted in terms of the Ga composition in the InGaP top cell, the existence of an InGaP thin shell laterally grown around the InP bottom cell, and the associated strain, and the role of doping in the luminescence emission of the InP bottom cell. It should be noted that while the photoelectric characteristics of these NWs are not directly addressed in this work, relevant data for similar NWs can be found in the literature for interested readers [15,16].…”