Core-shell Solar Cells Research Articles

Impact of Interface Recombination on Quantum Efficiency of a‐Si:H/c‐Si Solar Cells Based on Si Wires

Core–Shell Solar Cells In article number 2100339 by Alexander Gudovskikh and co-workers, the influence of interface states on the performance of a-Si:H/c-Si solar cells based on Si wires fabricated using a combination of latex sphere lithography and cryogenic dry etching is studied using simulation and experimental measurements. The key role of the Si wire geometry and doping density for sensitivity of quantum efficiency to interface states on the sidewall is demonstrated.

Design Principles for Fabrication of InP-Based Radial Junction Nanowire Solar Cells Using an Electron Selective Contact

Nanowire solar cells hold several advantages over planar solar cells, such as reduced reflection, facile strain relaxation, extreme light trapping, increased defect tolerance, etc. However, because of their large surface-to-volume ratio, nanowires tend to have very low effective minority carrier lifetime. To overcome this issue, a radial junction solar cell was proposed. However, in experimental realization, the efficiency of a radial junction solar cell remains significantly lower than its axial counterpart. This is mainly because of the inability to simultaneously control the doping in both the core and the shell while maintaining low defect density at the interface. To overcome the above-mentioned issues, we propose and simulate a core–shell heterojunction solar cell using p-InP as a core material and ITO/ZnO as a shell material. Using finite-difference time-domain simulations, we show that use of an oxide coating over InP core can significantly increase the absorption in InP nanowire arrays, and for an optimized thickness of oxide layer, InP consumption can be reduced by as much as four folds without sacrificing the ideal short circuit current. In addition, our device simulation results show that even for a core minority carrier lifetime of 50 ps, an efficiency of 23% can be obtained if both core and shell can be heavily doped while maintaining an interface recombination velocity of less than 104 cm/s. Finally, we discuss how the proposed device structure can reduce the fabrication complexities related to epitaxial homojunction/heterojunction core–shell solar cell structure while achieving a high efficiency under optimized conditions.

Core–shell solar cell fabrication using heterostructure of ZnO-nanowires arrays decorated with sputtered CdTe-nanoparticles

Core–shell heterostructures of ZnO-NWs/CdTe-NPs were fabricated through covering ZnO-NWs arrays using CdTe-NPs and the room temperature RF magnetron sputtering method. The influence of different CdTe-NPs deposition time (5, 20, 40 and 60 min) on the physical properties of core–shell heterostructures were investigated. In order to achieve the highest coverage level and a wide range of optical absorption at a visible range for a ZnO-NWs/CdTe-NPs (60 min) array, FTO/ZnO-NWs/CdTe-NPs (60 min)/Ni/Au core–shell solar cells were used. Solar cell fabrication was performed by soaking the samples in a saturated CdCl2 solution in methanol and a post-annealing treatment at 400 °C for 1 h in air which led to grain growth, the passivation of deep level defects, and the decrease of stacking faults. Short-circuit current and power conversion efficiency of the fabricated cell under illumination with visible light AM1.5 (100 mW cm−2) were 13.3 mA cm−2 and 3.41%, respectively. It was found that introducing a thin interfacial layer of CdSe to the configuration (FTO/ZnO-NWs/CdSe (10 nm)/CdTe-NPs (60 min)/Ni/Au) led to a 5.58% enhancement of photovoltaic performance of the solar cell (20.9 mA cm−2), which is 63.6% more than that of the same configuration without CdSe.

Solid state p-type dye sensitized NiO–dye–TiO2 core–shell solar cells

Solid state p-type dye sensitized NiO-dye-TiO2 core-shell solar cells with an organic dye PB6 were successfully fabricated for the first time. With Al2O3 as an inner barrier layer, the recombination process between injected holes in NiO and injected electrons in TiO2 was significantly suppressed and the charge transport time was also improved.

Two-Dimensional Modeling of Silicon Nanowires Radial Core-Shell Solar Cells

Silicon nanowires radial core-shell solar cells have recently attracted significant attention as promising candidates for low cost photovoltaic application, benefit from its strong light trapping, and short radial carrier collection distances. In order to establish optics and electricity improvement, a two-dimensional model based on Shockley-Read-Hall recombination modes has been carried out for radial core-shell junction nanowires solar cell combined with guided resonance modes of light absorption. The impact of SiNWs diameter and absorption layer thickness on device electrical performance based on a fixed nanowires height and diameter-over-periodicity were investigated under illumination. The variation in quantum efficiency indicated that the performance is limited by the mismatch between light absorption and carriers’ collection length.

The influence of passivation and photovoltaic properties of α-Si:H coverage on silicon nanowire array solar cells

Silicon nanowire (SiNW) arrays for radial p-n junction solar cells offer potential advantages of light trapping effects and quick charge collection. Nevertheless, lower open circuit voltages (Voc) lead to lower energy conversion efficiencies. In such cases, the performance of the solar cells depends critically on the quality of the SiNW interfaces. In this study, SiNW core-shell solar cells have been fabricated by growing crystalline silicon (c-Si) nanowires via the metal-assisted chemical etching method and by depositing hydrogenated amorphous silicon (α-Si:H) via the plasma-enhanced chemical vapor deposition (PECVD) method. The influence of deposition parameters on the coverage and, consequently, the passivation and photovoltaic properties of α-Si:H layers on SiNW solar cells have been analyzed.

A baseball-bat-like CdTe/TiO2 nanorods-based heterojunction core–shell solar cell

Rutile TiO 2 nanorods on fluorine-doped thin oxide glass substrates via the hydrothermal technique were synthesized and decorated with a sputtered CdTe layer to fabricate a core–shell type n-TiO 2 /p-CdTe solar cell. Absorbance spectrum verified the absorption contribution of both TiO 2 and CdTe to the absorption process. The solar cell parameters, such as open circuit voltage, short circuit current density, fill factor and power conversion efficiency were found to be 0.34 V, 1.27 mA cm −2 , 28% and 0.12%, respectively.

High-efficiency core–shell solar cell array from Si wafer

High-efficiency micro core–shell solar cell (μ-CSSC) arrays are fabricated from Si wafer by using traditional lithography and phosphorus diffusion. The p–n junction depth is around 450 nm, indicating that it forms core–shell structure in micropillars by using phosphorus diffusion. The μ-CSSC arrays have high minority carrier lifetime of 23 μs and long diffusion length of ∼150 μm. The best power efficiency of the μ-CSSC reaches to 9.2%. It is a convenient method for fabricating Si μ-CSSC arrays in wafer scale for future applications.

Hybrid density functional study of band alignment in ZnO–GaN and ZnO–(Ga1−xZnx)(N1−xOx)–GaN heterostructures

The band alignment in ZnO/GaN and related heterostructures are crucial for the uses in solar harvesting technology. Here, we report our density functional calculations of the band alignment and optical properties of ZnO/GaN and ZnO/(Ga1-xZnx)(N1-xOx)/GaN heterostructures using a Heyd-Scuseria-Ernzerhof (HSE) hybrid functional. We found that the conventional GGA functionals underestimate not only the band gap but also the band offset of these heterostructures. Using the hybrid functional calculations, we show that the (Ga1-xZnx)(N1-xOx) solid solution has a direct band gap of about 2.608 eV, in good agreement with the experimental data. More importantly, this solid solution forms type-II band alignment with the host materials. A GaN/(Ga1-xZnx)(N1-xOx)/ZnO core-shell solar cell model is presented to improve the visible light adsorption ability and carrier collection efficiency.