Realizing High-Efficiency Omnidirectional n-Type Si Solar Cells via the Hierarchical Architecture Concept with Radial Junctions

Abstract

Hierarchical structures combining micropyramids and nanowires with appropriate control of surface carrier recombination represent a class of architectures for radial p-n junction solar cells that synergizes the advantageous features including excellent broad-band, omnidirectional light-harvesting and efficient separation/collection of photoexcited carriers. The heterojunction solar cells fabricated with hierarchical structures exhibit the efficiency of 15.14% using cost-effective as-cut Czochralski n-type Si substrates, which is the highest reported efficiency among all n-type Si nanostructured solar cells. We also demonstrate the omnidirectional solar cell that exhibits the daily generated power enhancement of 44.2% by using hierarchical structures, as compared to conventional micropyramid control cells. The concurrent improvement in optical and electrical properties for realizing high-efficiency omnidirectional solar cells using as-cut Czochralski n-type Si substrates demonstrated here makes a hierarchical architecture concept promising for large-area and cost-effective mass production.

Stable solar-driven oxidation of water by semiconducting photoanodes protected by transparent catalytic nickel oxide films

“…4C shows the wavelength (λ)-dependent external quantum yield (Φ ext ) for HTJ-SijNiO x , n-CdTejNiO x , and a-Si:HjNiO x photoelectrodes maintained potentiostatically at 1.93 V vs. RHE, at which the light-limited current density was produced. The quantum yields of the HTJ-SijNiO x structure were higher than the values reported for analogous HTJ-Si-based solid-state devices (39). The higher value of Φ ext can be ascribed primarily to the antireflective behavior and broadband suppression of reflection by the NiO x film on the textured HTJ-Si surface maintained under working conditions.…”

“…The higher value of Φ ext can be ascribed primarily to the antireflective behavior and broadband suppression of reflection by the NiO x film on the textured HTJ-Si surface maintained under working conditions. The decrease in Φ ext at low and high wavelengths, respectively, was primarily attributable to recombination at the textured front and back interfaces between the crystalline Si and the a-Si surface passivation layer (39). The low blue response was also associated with absorption by the a-Si heterogeneous coating.…”

“…A load-line analysis using an equivalent-circuit model consisting of a photodiode connected in series with a dark electrolysis cell indicated that obtaining shifts in the J-E properties equivalent to those observed for the champion HTJ-SijNiO x photoanode in 1.0 M KOH(aq) relative to that of the p + -SijNiO x would require the use of a 9.0% efficient Si PV cell with a V oc = 600 mV, a shortcircuit current density (J sc ) of 34.0 mA·cm −2 , and a fill factor of 0.42 (1,38). The performance of the PV-biased electrosynthetic photoelectrode was lower than that of the solid-state PV device (39,40), likely due to nonideality of the back contact in conjunction with additional front-contact resistance in the amorphous Si layer and surface passivation that was partially degraded during the deposition of the NiO x , both of which led to increased recombination (reduced carrier lifetime) at the front and back interfaces as revealed by a time-resolved microwave conductivity measurement (TRMC) (SI Appendix, Fig. S7).…”

Efficiency Enhancement of Silicon Heterojunction Solar Cells via Photon Management Using Graphene Quantum Dot as Downconverters

“…14 carrier lifetimes (up to the millisecond range), no light-induced degradation caused by boron-oxygen pair, and high impurity tolerance. [16][17][18][19][20][21] Despite the great success in developing high performance SHJ devices, a large number of photons are still wasted, leading to the significant power loss. It is reported that the total power loss is more than 20% of the current output power.…”

Black-Silicon on Micropillars with Minimal Surface Area Enlargement to Enhance the Performance of Silicon Solar Cells

“…Furthermore, a hierarchical structure combining micropyramids and nanowires has been reported for enhanced light-trapping [23, 24]. Nevertheless, little is known about decreasing the reflection of micropillars or that of low-reflective b-Si having a low surface area.…”