Enhanced Cu₂S/CdS Coaxial Nanowire Solar Cells by Piezo-Phototronic Effect

Abstract

Nanowire solar cells are promising candidates for powering nanosystems and flexible electronics. The strain in the nanowires, introduced during growth, device fabrication and/or application, is an important issue for piezoelectric semiconductor (like CdS, ZnO, and CdTe) based photovoltaic. In this work, we demonstrate the first largely enhanced performance of n-CdS/p-Cu 2 S coaxial nanowire photovoltaic (PV) devices using the piezo-phototronics effect when the PV device is subjected to an external strain. Piezo-phototronics effect could control the electron−hole pair generation, transport, separation, and/or recombination, thus enhanced the performance of the PV devices by as high as 70%. This effect offers a new concept for improving solar energy conversation efficiency by designing the orientation of the nanowires and the strain to be purposely introduced in the packaging of the solar cells. This study shed light on the enhanced flexible solar cells for applications in self-powered technology, environmental monitoring, and even defensive technology. KEYWORDS: Cu 2 S/CdS coaxial nanowire, nanowire PV devices, piezo-phototronics effect, enhanced energy conversion efficiency S earching for renewable and green energy is one of the most urgent challenges to the sustainable development of human civilization owing to the threat of global warming and energy crises. Solar is probably the most abundant clean and renewable energy. Semiconductor nanowires (NWs) have a lot of advantages as candidates for photovoltaic (PV) applications 1−3 due to their large surface-to-volume ratio, better charge collection, 4 and the possibility of enhanced absorption through light trapping; 5,6 at the other side, nanowires will cause large surface and interface recombination, which could be overcome by surface passivation 7 and epitaxial growth of p−n junctions. 8 NWs-based PV has great application in flexible power source compared to bulk materials. In such case, the strain in the NWs, introduced during growth, device fabrication, and/or application, is an important issue for piezoelectric semiconductor (like CdS, ZnO, and CdTe) based PVs. Although theoretical study has predicted piezoelectric effect on NW PV, 9 experimental verification is still unavailable. Here, we report the enhanced performance of the piezoelectric n-CdS/p-Cu 2 S core−shell NW PV devices by a factor of 70% using the piezo-phototronic effect, which could control the electron−hole pair generation, transport, separation, and/or recombination at p−n junction via applied strain, thus tuning the performance of the PV devices. This effect offers a new concept for increasing solar energy conversion efficiency and has a bright future in the applications of flexible solar cell and self-powered technology.NW photovoltaics (PV) have been the subject of research for enhancing the energy conversion efficiency and possibly reducing the material and fabrication costs. The core−shell geometry of NWs is proposed to be able to enhance the efficiency of charge collection by...

All-in-one energy harvesting and storage devices

“…159 Thus, the coupling effect between mechanical, thermal, and light energy in an enhanced synergetic energy harvesting system has attracted great attention, as it is not just simple multi-type energy harvesting, and because such devices will offer a promising approach for effectively harvesting multi-type energy for realizing multi-functional energy devices. 134,138,[155][156][157][158][159][160][161][162][163][164] …”

Theoretical Study of Piezo‐phototronic Nano‐LEDs

“…As both the density and total amount of piezo-charges are dependent only on piezoelectric coeffi cient of the material and the existing strain, and independent of the doping profi le of the material, this assumption is valid when the doping profi le is low so that the total amount of depletion charges of the unstrained structure is far greater than the total amount of piezo-charges. Referring to experiments, this assumption is applicable to hydrothermally grown NWs with abundant defects as well as photodetectors and solar cells with photoexcited free charge carriers, [ 5,12 ] as the depletion-charge amount in these materials is far larger than that of piezo-charges under experimental straining conditions. However, in our simulation, the doping profi le is low, such that the total amount of intrinsic depletion charge is much smaller than the amount of piezo-charges at the junction interface.…”

“…[ 2 ] The performance of such devices can be tuned by applying external mechanical stress/strain, which gives rise to new scientifi c phenomena and technological applications. Many reports have detailed observations of the piezo-phototronic effect and its impact on optoelectronic processes, including signifi cant responsivity enhancement in photodetection, [ 3 ] output optimization of photocells, [ 4 ] improvement of solar-cell efficiency, [ 5 ] and most importantly, enhancement of the light-emission effi ciency of inorganic light-emitting diodes (LEDs) and inorganic/organic hybrid LEDs. [ 1,[6][7][8] An analytical model has also been proposed for the piezo-phototronic effect in metalsemiconductor structures.…”

Cu2S nanoparticles modified 3D flowerlike Bi2WO6: Enhanced photoelectric performance and photocatalytic degradation

“…Besides, the nano-sized particles can be spatially separated on the 3D Bi 2 WO 6 and give rise to a low NPs lose rate in the pollutant degradation process [4] . Cu 2 S NPs as a p-type semiconductor with a high optical absorption coefficient has been considered to be a much ideal sunlight-absorbing material for light conversion [5] and high efficiency photocatalysis.…”