c-Si/n-ZnO-based flexible solar cells with silica nanoparticles as a light trapping metamaterial

Abstract

Herein, we report the fabrication of flexible solar cells based on a crystalline p-Si/n-ZnO heterostructure for the first time. An enhancement of ∼52% in the base efficiency was achieved by the application of spherical SiO nanoparticles as light trapping structures on the top. The use of ZnO not only offers a facile route of synthesis, but also provides an additional advantage of large band bending, leading to notable open circuit voltage and formation of an intermediate ultra-thin barrier layer of ZnSiO for minimized carrier recombination. The spherical silica nanoparticles act as nanoresonators, causing absorption hot-spots in the thin silicon absorber, along with the capability of providing wide-angle light-collection. Simulation showed, for the higher angle of incidence, that the silica nanoparticles have the ability to bend light on the same side of the normal to the incident wave-front, thereby acting as a negative index metamaterial (NIM). The flexibility and cost-effectiveness of this device can make it important for the next-generation photovoltaics and roll-to-roll electronics.

Design and Validation of Multidimensional Hybrid Metamaterial Embedded Light Trapping Structure for p-Si/n-ZnO Based Thin c-Si Solar Cell

“…Through the previous studies it was already established the light trapping capability of multilayer silica nanoparticles. But further due decreasing the material cost adopted by simple fabrication method, monolayer of silica nanoparticles on top of the heterojunction solar cell was investigated through this work [8].…”

“…6 and 7) it can quite clear that in higher angle of incidence light, the silica nanoparticles act as metamaterial Mie resonators which have better ability to harvest more photons into the junction compared to previous two cases. The monolayer of silica nanoparticles has the capacity to bend light rays more pro ciently like negative indexed metamaterial which produce better results with more hotspots that is very near to the junction of the device [8,17]. So, it is quite evident that, this type of device structure shows better competent to inject more photons into the device in the higher angle of light compared to zero degree incidence.…”

Flexible and stretchable inorganic solar cells: Progress, challenges, and opportunities

“…The thinning down of Si can be achieved through different techniques, including back etching, 28 XeF 2 etching 29,30 or etching and exfoliation methods. 31 In this case, the thin substrate is used as an active layer of the solar cell where the intrinsic and n-type regions are deposited on top of it. Different materials for the n-type material in the solar cell have been studied, including a-Si where the degradation of minority carrier lifetime due to sputtering is minimized by optimizing the DC plasma power [ Fig.…”

“…20 In addition, ZnO is studied as the n-type material where an efficiency of around 2.73% was achieved. 31 Even though this technique provides access to a crystalline silicon layer with enhanced electronic properties compared with its amorphous counterpart, the main disadvantage of this approach, similar to that of ultra-thin glass, is the limited bendability of the flexible silicon substrate in addition to the challenge of handling without cracking it. Moreover, since in this case a costly silicon wafer is used in addition to having a large portion of it getting etched away and thus wasted, this technique is considered more expensive than the development of a-Si thin film-based solar cells on low cost substrates such as metal foils and some plastics.…”

Nanostructured back reflectors for improved light absorption in silicon thin film solar cells

“…Surface nanostructures like silver/gold NPs [197] [198], SiO2 nanospheres [199], TiO2 nanostructures [200], Si nanowires [102], etc. were intensively researched and the experimental results obtained have proven to be effective in enhancing light trapping performance.…”