Conductive-probe atomic force microscopy as a characterization tool for nanowire-based solar cells

Abstract

A B S T R A C TThe photonic properties of nanowires advocate for their utilization in next generation solar cells. Compared to traditional devices, the electric scheme is transformed from a single into an ensemble of pn junctions connected in parallel. This new configuration requires new schemes for the characterization. We show how conductiveprobe atomic force microscopy, C-AFM, is an essential tool for the characterization and optimization of this parallel-connected nanowire devices. With C-AFM it is possible to obtain both surface topography and local electrical characterization with nanoscale resolution. We demonstrate topography and current mapping of nanowire forests, combined with current-voltage measurements of the individual nanowire junctions from the ensemble. Our results provide discussion elements on some factors limiting the performance of a nanowire-based solar cell and thereby to provide a path for their improvement.

Unleashing the potential of molecular beam epitaxy grown AlGaN-based ultraviolet-spectrum nanowires devices

“…The conductive tip, being smaller than the NWs diameter, enables high-resolution measurement of individual NWs and large area statistical mapping. The technique has previously been explored in NWs solar cells, 161,162 in nanogenerators, [163][164][165][166] and only recently on group-III nitride AlGaN-based UV NWs-LEDs.…”

Observation of photovoltaic effect within locally doped silicon nanojunctions using conductive probe AFM

“…In particular, in the field of PV, local scale C-AFM investigations (in dark and illuminated conditions) have demonstrated added value in understanding charge transport and in improving the performance of the final device. Numerous C-AFM studies have been carried out on different solar cell configurations (planar, nanowires, cross-section, …) and in particular, on the layers or structures of which they are composed [26][27][28][29][30][31][32]. In this work, the C-AFM method will be used to directly probe the photovoltaic properties of nanojunctions formed in a c-Si wafer.…”

n‐Doped InGaP Nanowire Shells in GaAs/InGaP Core–Shell p–n Junctions

“…And, in core–shell NWs, depending on the excitation energy, the shell and core materials are penetrated simultaneously, which further complicates the analysis. Electrical analysis by scanning probe microscopy allows for contact‐independent doping profiling of semiconductors via scanning capacitance measurements and has been used for electrical NW characterization . Another technique is the ultrahigh vacuum (UHV) multi‐tip scanning tunneling microscopy (MT‐STM), which offers the possibility to enable contact area‐independent resistance profiling along tapered NWs when used as a four‐point prober .…”