Carbon@Tellurium Nanostructures Anchored to a Si Nanowire Scaffold with an Unprecedented Liquid-Junction Solar Cell Performance

Abstract

Silicon nanowire (SiNW) arrays offer a range of exciting opportunities, from maximizing solar spectrum utilization for high-performance liquid-junction solar cells (LJSCs) to functioning as potential micro-supercapacitors in the near future. This work, contrasting strongly with the previously reported studies on SiNW-based LJSCs where electron-conducting nanoparticles of Pt or Au were employed to achieve high efficiencies, aims at tethering relatively inexpensive, hole-conducting, and photoresponsive carbon-coated tellurium nanorods (C@TeNRs) to SiNWs in the quest to achieve an outstanding solar cell performance. A SiNW LJSC (control cell) with a SiNWs/Br–, Br2/carbon-fabric architecture delivers a power conversion efficiency (PCE) of 4.8%. Further, by anchoring C@TeNRs, along the lengths of SiNWs via electrophoresis, a PCE of ∼11.6% is attained for a C@TeNRs@SiNWs/Br–, Br2/carbon-fabric-based LJSC. The multifunctionality of C@Te comes to the fore in this cell where (1) the p-type (hole) conducting nature of C@Te ensures efficient charge separation by rapidly collecting holes from SiNWs (and suppresses recombination), (2) the C@TeNRs are also photoresponsive and increase light-harvesting, and (3) the C coating restricts the chemical corrosion and photo-oxidation of SiNWs and the Te core by the acidic electrolyte, thereby improving the cell’s operational lifetime. This LJSC also serves as an effective stand-alone energy-storage device giving an improved areal specific capacitance of 1605 μF cm–2 (at 1 mA cm–2). This study unravels the pivotal role played by C@TeNRs in controlling the performance of SiNW-based LJSCs.

CoS Nanoflakes on Textured Silicon Coupled with Antimony-Decorated Tungsten Oxide for Efficient Liquid Junction Solar Cells

“…A detailed comparison of LJSCs/PECs and solid-state devices based on Si nanostructures is presented in Table S7 (Supporting Information). While PCEs in the range of 0.3–16% are reported for different configurations, − the associated stability information is provided only in very few reports. ,,− ,,,,, Among solid-state devices, while a PCE as high as ∼13% is reported for an Ag/SiNW/V 2 O 5 /Al solar cell, stabilities are not reported very well . Only two reports carry some data.…”

“…Liquid junction solar cells (LJSCs) based on modified n-Si are an economically viable option for efficient photo-conversion devices. Black Si electrodes, even when characterized by a high defect proportion, can still easily deliver high power conversion efficiencies (PCEs, in excess of 10%) when used as the photoanode in LJSCs, − thus highlighting their defect tolerant nature. Planar Si-based p/n junction cells do not offer this advantage.…”

“…The LJSC architecture comprises an n-Si-based photoanode, an HTL (liquid or semisolid), and an electrocatalytic counter electrode (CE). − Here, to reduce the recombination at the T-Si/electrolyte interface, the T-Si photoanode was further modified by coating p-type CoS nanoflakes, which besides serving as photosensitizers, play a pivotal role in transmitting photo-generated holes from T-Si to the reduced electrolyte species. In the past, to achieve a good photo-electrochemical (PEC) response, black Si nanostructure-based electrodes have been modified with Pt nanoparticles (NPs), ,, Au NPs, electrically conducting Ag film, double-walled nanotubes, graphene, , Se NPs, C@Te nanorods, and so on. These examples provided the impetus to use CoS nanoflake-modified T-Si as the photoanode, which has never been used in a Si-LJSC before.…”

Efficient Charge Separation Enabled by N-Doped Graphene Quantum Dots and PCDTBT for a High-Performance Silicon Nanowire Solar Cell

“…SeNPs were photoactive and also permitted hole transfer from the SiNW to the electrolyte, and the resulting cell showed a power conversion efficiency (PCE) of 7.03% . The LJSC configuration was further improved by replacing SeNPs with carbon-coated tellurium nanorods (C@TeNRs), and due to their high photoconductivity and superior hole collection efficiency, a PCE of 11.5 ± 0.1% was achieved …”

“…16 The LJSC configuration was further improved by replacing SeNPs with carboncoated tellurium nanorods (C@TeNRs), and due to their high photoconductivity and superior hole collection efficiency, a PCE of 11.5 ± 0.1% was achieved. 17 The present study deals with modifying not just the photoanode but also the CE using relatively nontoxic and easily available components without compromising the performance, for both Se and Te are toxic and rare elements. 18 A novel, yet unreported photoanode architecture comprising of hole-conducting p-type nitrogen-doped graphene quantum dots (N-GQDs) and poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) as the co-sensitizer anchored to the SiNW is presented in this study.…”