Control of zinc oxide nanowire array properties with electron-beam lithography templating for photovoltaic applications

Abstract

Hydrothermally synthesized zinc oxide nanowire arrays have been used as nanostructured acceptors in emerging photovoltaic (PV) devices. The nanoscale dimensions of such arrays allow for enhanced charge extraction from PV active layers, but the device performance critically depends on the nanowire array pitch and alignment. In this study, we templated hydrothermally-grown ZnO nanowire arrays via high-resolution electron-beam-lithography defined masks, achieving the dual requirements of high-resolution patterning at a pitch of several hundred nanometers, while maintaining hole sizes small enough to control nanowire array morphology. We investigated several process conditions, including the effect of annealing sputtered and spincoated ZnO seed layers on nanowire growth, to optimize array property metrics -branching from individual template holes and off-normal alignment. We found that decreasing template hole size decreased branching prevalence but also reduced alignment. Annealing seed layers typically improved alignment, and sputtered seed layers yielded nanowire arrays superior to spincoated seed layers. We show that these effects arose from variation in the size of the template holes relative to the ZnO grain size in the seed layer.The quantitative control of branching and alignment of the nanowire array that is achieved in this study will open new paths toward engineering more efficient electrodes to increase photocurrent in nanostructured PVs. This control is also applicable to inorganic nanowire growth in general, nanomechanical generators, nanowire transistors, and surface-energy engineering.2

Enhanced Photocurrent in PbS Quantum Dot Photovoltaics via ZnO Nanowires and Band Alignment Engineering

“…[17] However, the fact that nanowire devices have a lower V OC than planar devices, despite their higher J SC , indicates that recombination at the junction may contribute to additional V OC loss due to the larger interface area in nanowire devices compared to planar devices. [42,43] In conclusion, we have demonstrated a device architecture that combines a ZnO nanowire array OBHJ architecture with band alignment engineering of the PbS QD film to promote charge extraction. [41] Furthermore, while these ZnO nanowire arrays show good alignment and uniformity, further work can be done to optimize the alignment, length and pitch of solution-grown ZnO nanowire arrays on transparent conducting oxides to optimize their current collection and light trapping properties for application in QD PVs.…”

Review—Growth of Al-, Ga-, and In-Doped ZnO Nanostructures via a Low-Temperature Process and Their Application to Field Emission Devices and Ultraviolet Photosensors

“…9,10 Among these approaches, the hydrothermal method and aqueous solution methods are the least expensive and the simplest for synthesizing ZnO nanostructures. The various morphologies of ZnO 1D nanostructures include nanopins, 11 nanorods (NRs), 12 nanotubes, 13 and nanowires (NWs).…”

High selectivity to ethanol gas sensor based on ZnO nanosheets decorated with Ag nanoparticles by aqueous solution and photochemical deposition

“…Among of them, the various morphologies of ZnO include nanodiscs, nanowires (NWs), nanotubes, nanorods (NRs), nanoplates, nanopins, and nanosheets (NSs) have also been fabricated [5][6][7][8][9][10][11] . ZnO nanostructure have many synthetic methods, such as hydrothermal method (HTM), chemical vapor deposition (CVD), aqueous solution methods (ASM), pulsed laser deposition (PLD), electrochemical deposition (ECD), and electron-beam lithography (EBL) 8,[12][13][14][15][16][17][18][19] . Currently, ZnO nanostructures have been applied to optical and electronic devices, such as field-effect transistors (FETs), UV photodetectors (UV PD), light emitting diodes (LEDs), glucose sensors, varistors devices, gas sensors [20][21][22][23][24][25][26][27][28] .…”