Solution-processed core–shell nanowires for efficient photovoltaic cells

Abstract

Semiconductor nanowires are promising for photovoltaic applications, but, so far, nanowire-based solar cells have had lower efficiencies than planar cells made from the same materials, even allowing for the generally lower light absorption of nanowires. It is not clear, therefore, if the benefits of the nanowire structure, including better charge collection and transport and the possibility of enhanced absorption through light trapping, can outweigh the reductions in performance caused by recombination at the surface of the nanowires and at p-n junctions. Here, we fabricate core-shell nanowire solar cells with open-circuit voltage and fill factor values superior to those reported for equivalent planar cells, and an energy conversion efficiency of ∼5.4%, which is comparable to that of equivalent planar cells despite low light absorption levels. The device is made using a low-temperature solution-based cation exchange reaction that creates a heteroepitaxial junction between a single-crystalline CdS core and single-crystalline Cu2S shell. We integrate multiple cells on single nanowires in both series and parallel configurations for high output voltages and currents, respectively. The ability to produce efficient nanowire-based solar cells with a solution-based process and Earth-abundant elements could significantly reduce fabrication costs relative to existing high-temperature bulk material approaches.

Piezo‐Phototronic Effect Enhanced Flexible Solar Cells Based on n‐ZnO/p‐SnS Core–Shell Nanowire Array

“…Photovoltaic that converts sunlight to electricity is one of the promising technologies to solve the energy problem that our society faces in the near future. Because semiconductor nanowires (NWs) have a lot of advantages such as large surface‐to‐volume ratio, better charge collection,1 and the possibility of enhanced absorption through light trapping,2 so that NWs‐based photovoltaics (PV) have been the subject of research for enhancing the energy conversion efficiency 3. On the other hand, nanowires will cause large surface and interface recombination, which could be overcome by surface passivation and epitaxial growth of p‐n junctions 4, 5.…”

Large-Scale Synthesis of Transition-Metal-Doped TiO2 Nanowires with Controllable Overpotential

“…[1][2][3][4][5][6][7][8][9] Many synthetic methods have been developed for growing one-dimensional (1D) semiconductors, including vaporliquid-solid (VLS), 10,11 vapor-solid (VS), 12 solution-liquid-solid (SLS), 13 and hydrothermal/solvothermal techniques. [14][15][16] However, these methods typically trade either yield for quality or vice versa.…”

Design of Nanowire Optical Cavities as Efficient Photon Absorbers

“…[10][11] In addition, semiconductor NW photovoltaics (PV) are emerging as a promising platform for the next generation solar cells that require a high efficiency at costs approaching grid parity. [12][13][14][15][16][17][18][19] In particular, p/i/n core-shell NWs demonstrate electrical and optical properties distinct from conventional planar materials: radial minority carrier separation with short diffusion lengths, and enhanced light absorption resulting from the cavities' subwavelength size. [12][13][14] Recently, crystalline Si NW PVs have been successfully demonstrated, exhibiting good electrical characteristics as represented by an open-circuit voltage of ~0.5V and very low leakage current of 1 fA.…”

“…[12][13][14]17,[20][21][22][23][24][25][26][27] For example, absorption or scattering cross sections have been estimated qualitatively, 17,[20][21][22][23] while in other works wavelength-dependent photocurrent measurements performed on single NW PV devices were used to assign quantitatively the resonances of NW optical cavities. [13][14][15] Concurrent with experiments, numerical and analytical calculations of the resonant modes and key optical figures of merit (e.g. absorption efficiency and scattering cross section) for NW optical cavities have been reported.…”