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In this work, the design and fabrication of a Cu/p-Si/Pt Schottky photodetector with a simple structure is investigated. The mechanism of electron flow is explained using internal photoemission theory, which is further applied to make the fabricated devices reach a high responsivity of 0.542 mA/W at 0–V bias. The investigation revealed that the rapid thermal annealing process could significantly influence the device characteristics. Variations in Schottky barrier height and series resistance of the photodetectors were also analyzed and correlated with the device responsivity. With proper conditions to improve the Pt/Si ohmic contact, the device performance can be enhanced.

Here, inverted-pyramid array structures (IPAS) are applied on NiSi/n-Si Schottky photodetectors to generate surface plasmon resonance and improve the photoresponse in mid-infrared region. Consequently, compared with the planar devices, the current response of 8-$\mu$m-period IPAS devices increases 4.08 times in 3.2-$\mu$m light illumination.

Nowadays, infrared (IR) photodetectors are mainly made from compound semiconductors due to the bandgap flexibility. However, compound semiconductors are mostly synthesized by expensive and energy-intensive epitaxy processes. Moreover, compound semiconductors are difficult to integrate with Si-based IC industry. Therefore, we used n-type Si (n-Si) wafers and thin NiSi to combine with localized surface plasmon resonance (LSPR) to form a Schottky IR detector. The incident IR light can induce thermionic effect to generate photocurrent, and the LSPR can enhance the light absorption and improve the photoresponse. The LSPR was created by NiSi covered inverted-pyramid array structures (IPAS) formed on n-Si substrates through photolithography and etching processes. After IPAS were prepared, 10-nm-thick Ni was thermally deposited on the IPAS and then the entire samples were annealed under 500 °C in 5 s to form NiSi/n-Si Schottky junctions. Finally, Ti and Au were thermally deposited successively on the NiSi and the back of n-Si wafers to be electrodes. A planar device was also prepared to be a control part. The photodetection ability of the device was examined by a 4.8-μm IR source with 1.8-mW optical power, which is in the absorption range of carbon monoxide. The IR source was turned on/off for each 15 s. Consequently, the planar NiSi/n-Si Schottky photodetector shows average 9.37-μA current change under 4.8-μm IR source illumination in 15 s. However, if 8-μm-period IPAS was used, the average current change improved to 30.9 μA. The response enhancement is 3.30 times of the planar device.

Nowadays, compound semiconductors are the main approach to detect mid-infrared (IR) light, such as HgCdTe and InAsSb, due to the bandgap tunability compared with Si. However, the epitaxy processes are expensive and energy-intensive. Also, compound devices are not compatible with Si-based IC manufacturing. To solve those problems, here, we apply inverted pyramid array structures (IPAS) to induce localized surface plasmon resonance (LSPR) for Si-based Schottky devices. While IR illuminates metal covered IPAS (metal-IPAS), the photo-electrons can accumulate photon energy repeatedly through IPAS induced LSPR. While the electron energy is large enough to overcome the Schottky barrier, so the photo-current is generated. Regarding device preparation and measurement, briefly, the IPAS were formed on n-type Si (n-Si) substrates through photolithography, dry etching, and wet etching. Afterward, 10-nm-thick Ag films and 100-nm-thick Ag grid anode were thermally deposited on the IPAS successively to form Schottky junctions. Finally, Al was thermally deposited on the back of n-Si wafers to be the cathode. After device fabrication, the devices were illuminated by a 4010 nm mid-IR pulse laser, generated from a 1064 nm pulse laser through an optical parametric generator. The photo-voltage of the device induced by the mid-IR was measured by an oscilloscope. Consequently, the oscilloscope showed a short pulse while the device was illuminated by the 4010 nm pulse laser. The rising time is 8 ns, and the amplitude is 10.2 mV. The result reveals that the metal-IPAS induced LSPR successfully detects mid-IR light with photon energy less than Schottky barrier height.

Infrared (IR) photodetector is widespread applied to spectroscopy, biosensing, and image detection. Nowadays, most of IR photodetectors are prepared from compound semiconductors, for example, SiGe, HgCdTe, and InSb. However, most of them are formed through high energy consumption and high expense processes, such as chemical vapor deposition. Also, compound devices are not compatible with Si-based IC manufacturing and very expensive. Therefore, here, we used n-type Si (n-Si) wafers and Ag thin films to form a Schottky IR detector. The detection principle is using IR source to induce thermionic effect on Schottky diode and then the scattering of photoelectrons excited by IR and visible light, respectively, induces current difference. Regarding device preparation, at first, the native oxide on n-Si wafers was removed by buffer HF; then the 10-nm-thick Ag films and 100-nm-thick Ag grid anode were thermally deposited on the n-Si successively. Afterward, Al was thermally deposited on the opposite side of n-Si wafers to be a cathode. The electric property of devices was determined through current-to-time (I-T) measurement with an 80-mW green laser illuminating on the Ag side constantly. A 3.22-μm IR source was illuminated through Ag side but turned on/off for each 5 s. The electric bias is 0 V. Consequently, if no green laser exposing, current increased after IR turned on due to the pure thermionic effect and the responsivity is 1.8 mA/W. While the green laser illuminating constantly, current decreased after IR turned on, and the responsivity increased to -15.7 mA/W.

This paper experimentally demonstrates the benefits of combining an up-conversion (UC) layer containing Yb/Er-doped yttrium oxide-based phosphors with a plasmonic scattering layer containing indium nanoparticles (In-NPs) in enhancing the photovoltaic performance of textured silicon solar cells. The optical emissions of the Yb/Er-doped phosphors were characterized using photoluminescence measurements obtained at room temperature. Optical microscope images and photo current-voltage curves were used to characterize the UC emissions of Yb/Er-doped phosphors under illumination from a laser diode with a wavelength of 1550 nm. The plasmonic effects of In NPs were assessed in terms of absorbance and Raman scattering. The performance of the textured solar cells was evaluated in terms of optical reflectance, external quantum efficiency, and photovoltaic performance. The analysis was performed on cells with and without a UC layer containing Yb/Er-doped yttrium oxide-based phosphors of various concentrations. The analysis was also performed on cells with a UC layer in conjunction with a plasmonic scattering layer. The absolute conversion efficiency of the textured silicon solar cell with a combination of up-conversion and plasmonic-scattering layers (15.43%) exceeded that of the cell with an up-conversion layer only (14.94%) and that of the reference cell (14.45%).

In this paper, the interface between Si nanoholes (SiNHs) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is investigated and improved to achieve high-efficiency SiNH/PEDOT:PSS hybrid solar cells. The high-density SiNHs are fabricated using short-time Ag deposition before metal-assisted chemical etching (MacEtch) method. Also, a polymer coverage method is explored to overcome the difficulty of PEDOT:PSS infiltration into SiNHs. PEDOT:PSS is mixed with co-solvent dimethylsulfoxide (DMSO) to have better polymer infiltrate into SiNHs via two-step coating process. This technique significantly improves the interface between SiNHs and PEDOT:PSS; the greatly reduced contact angle from 90° to 16° at the interface of Si and PEDOT:PSS has established this fact. In addition, the minority carrier lifetime is dramatically increased from 31.52 to 317.20 μs. The property improvement enables the SiNH/PEDOT:PSS hybrid solar cell with high Jsc of 36.80 mA cm−2, Voc of 0.524 V, FF of 66.50%, and thus PCE of 12.82%. Also, the SiNH structures have an excellent light-trapping effect, which contributes to very low average total reflectance of 3%, due to internal multiple reflections caused by subwavelength features. At an angle of incidence up to 60°, the specular reflectance maintains at as low as 1%; even at a large angle of 70°, the reflectance is still below 10%. This work provides a feasible solution process to fabricate SiNH structure and to improve organic/Si hybrid solar cells in energy and cost-effective manner.

In this study, we fabricate uniform silicon nanowire (SiNW) arrays on 6-inch mono- and multi-crystalline wafers by employing the improved solution-processed metal-assisted chemical etching (MacEtch) method. Furthermore, the improved MacEtch can be applied to various crystalline orientation wafers. The SiNW arrays are 470 nm in length with high density; they demonstrate a good optical trapping effect and reflectance well below 6% over a broad wavelength range from 300 to 1100 nm. The improved MacEtch shows no difference in reflectance for a pyramid/SiNW mono-crystalline wafer with appropriate uniformity; the average delta from the center to other positions is within 22%. The effective lifetime is lower for SiNW arrays because the higher surface state causes higher surface recombination. Finally, we make the multi-crystalline wafer into an Al-BSF solar cell device with MacEtch SiNW texture, resulting in an averaged power conversion efficiency of 17.83%, which is higher than that of standard acid-textured solar cell devices. Consequently, the improved MacEtch concept is suitable for commercial mass production in the photovoltaic industry.

In this paper, we employ a series of metal-assisted chemical etching processes to fabricate low-cost silicon nanohole (SiNH) and silicon nanowire (SiNW) arrays for hybrid solar cells. The SiNH arrays and SiNW arrays are obtained by a two-step etching and one-step etching technique, respectively. Length and depth of SiNWs and SiNHs can be controlled by etching time. The SiNH arrays demonstrate higher optical trapping effect than SiNW arrays, resulting in leading performance power conversion efficiency of 11.25% in the hybrid organic–inorganic solar cells. SiNH arrays have a high surface area, compared to SiNW arrays, so they can give rise to more junction area in the organic–inorganic heterojunction structures. In addition, these SiNH arrays possess additional advantages of robust structures and higher density with low air-filling fraction as compared to SiNW arrays. Furthermore, the SiNH arrays show superior efficiency to SiNW arrays experimentally. In particular, the fabricated SiNH arrays with high density can suppress the optical reflection well below 5% over a broad wavelength range from 300 to 1100 nm in a short nanohole depth. The very low reflectance and excellent light trapping property are attributed to the sub-wavelength dimension of the SiNH structure. These SiNH arrays not only facilitate the optical trapping, but also provide efficient broadband and omnidirectional photon harvests for cost-effective future nanostructured photovoltaics.

We propose methods of enhancing the efficiency of organic hybrid silicon solar cells. First, we use two-step metal-assisted method to fabricate silicon nanostructures to reduce the reflectivity. However, the organic material (PEDOT:PSS) has large absorption of light, so the silicon absorption is reduced. To solve this problem, PEDOT:PSS is diluted using IPA before it is deposited. Nonetheless, the adhesion of the thin PEDOT is bad, so it cannot be used together with ITO glass. Then, we use silver nanowires (AgNWs) to improve the contact between PEDOT:PSS and front electrode. Finally, the hybrid silicon solar cells have improved efficiency of 13.37%.

In this study, light trapping of textured silicon solar cell based on light scattering and angle of incident light of plasmonics indium nanoparticles (In NPs) of various dimensions is demonstrated. The light trapping modes of textured surface with and without In NPs for incident angles of 0°, 35.3°, and 54.7° are proposed and characterized. The optical reflectance, external quantum efficiency and photovoltaic performance depended on the dimensions of plasmonics In NPs and angles of incident light are measured and compared.

Structures capable of exciting localized surface plasmon resonance (LSPR) have been widely utilized to increase photoresponse in many photoactive devices. However, most LSPR can be induced in only a small spectral range and with particular polarization. Here, LSPR with ultra-broadband response is revealed. Light detection using such LSPR is also explored to exhibit a spectral range covering the visible to mid-infrared. The strong LSPR induced by the inverted pyramid array structure enables a Si-based Schottky photodetector to detect photons even with energy lower than the Schottky barrier height, leading to the experimental measurement covering from 300 to 2700 nm. Theoretical evaluation even predicts a response beyond 4000 nm.

Compare with different thickness silicon thin film, 30μm, 50μm and 100μm, we demonstrate a promising way to form 30μm silicon thin film hybrid solar cells with good bending property, by using the silicon nanostructure (SiNS) to achieve low reflection and increase heterojunction areas, the device performance is enhanced to 10.15%.

In this work, we investigate in great detail the silicon nanowire (SiNW)/poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid solar cells (SCs). Because of the light-trapping effect, SiNW/PEDOT:PSS SCs absorb more light than planar Si/PEDOT:PSS SCs. Also, the light absorption increases with the length of the SiNWs. However, the SiNW's length is not the only factor that influences the SCs. Thus the SiNW/PEDOT:PSS SCs with the shortest wire length of 0.37 μm have the best performance in terms of the highest power conversion efficiency of 8.40%, the largest short circuit current density of 24.24 mA cm−2, and open circuit voltage of 0.532 V, compared with the SCs of other wire lengths. The reasons are two-fold. First, long SiNWs tend to aggregate at the top portion, making the infiltration of PEDOT:PSS difficult, so the coverage of PEDOT:PSS on the SiNWs is not complete. Second, the increase of SiNW length greatly reduces the minority-carrier lifetime. Our investigation will help develop SiNW SCs with improved performance.

Nanostructured silicon hybrid solar cells are promising candidates for a new generation photovoltaics because of their light-trapping abilities and solution processes. However, the performance of hybrid organic/Si nanostructure solar cells is hindered because of carrier recombination at surface and poor coverage of organic material poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PSS) on nanostructures. Here we demonstrate low-pressure-assisted coating method ofPSS on surface-modified silicon nanotips with broadband light-trapping characteristics to improve interface property and to achieve high-efficiency hybrid solar cells through a solution process. The approach enhances the effective minority-carrier lifetime and the coverage ofPSS on the surface of nanostructures. Hybrid solar cells fabricated with surface-modified nanotips exhibit a high fill factor of 70.94%, short-circuit current density of 35.36 mA/cm(2), open-circuit voltage of 0.528 V, and power conversion efficiency of 13.36%. The high efficiency and the high fill factor are achieved because of conformal coating ofPSS via a low-pressure-assisted coating process, excellent light harvesting without sacrificing the minority-carrier lifetime, and efficient charge separation/collection of photogenerated carriers.

This study experimental demonstrated the plasmonic effects of Al-, In-, and Ag-nanoparticles (NPs) depositing on the silicon solar cells, respectively, according to external quantum efficiency and photovoltaic current-voltage. Efficiency enhancement of 22.68%, 20.88% and 17.10% for the cell with In-, Al- and Ag-NPs was obtained, compared to the reference cell.

In this work, a simple solution process (metal-assisted wet chemical etching [MacEtch] method) is used to fabricate high-density silicon nanohole (SiNH) arrays on n-type wafer. SiNH arrays generally produce a large surface-area-to-volume ratio, so that aid for strong light trapping effect between the nanostructures causes high absorption and charge collection via the formation of a core-sheath p-n junction. However, the photogenerated excited carriers are easily trapped by high-density surface defects due to higher surface area prolonging to depth of nanohole (NH). To reduce the surface defects and metal contamination of SiNHs formed by metal-catalyst etching, it is important to further proceed to feasible simple solution treatment. Applying the chemical polishing etching (CPE) treatment to SiNH surface leads to smooth and contamination-free surface. In addition, all the processes mentioned here are energy and cost-efficient.

In this work, water, isopropyl alcohol (IPA), and Zonyl fluorosurfactant are applied on PEDOT:PSS to try to improve PEDOT:PSS attachment on Si nanowires (SiNWs) thoroughly. After treatment, only Zonyl fluorosurfactant assisted PEDOT:PSS has thorough coating profiles on SiNWs. However, water and IPA diluted PEDOT:PSS only touch the top portion of SiNWs. Therefore, Zonyl-PEDOT:PSS/SiNW solar cells generate highest PCE of 10.87%, Jsc of 28.86 mA/cm2, and FF of 71.75%. In comparison, the water-PEDOT:PSS/SiNW and IPA-PEDOT:PSS/SiNW devices have lower PCE of 9.22% and 8.66%, respectively.

In this study, we sought to improve the light trapping of textured silicon solar cells using the plasmonic light scattering of indium nanoparticles (In NPs) of various dimensions. The light trapping modes of textured-silicon surfaces with and without In NPs were investigated at an angle of incidence (AOI) ranging from 0° to 75°. The optical reflectance, external quantum efficiency (EQE), and photovoltaic performance were first characterized under an AOI of 0°. We then compared the EQE and photovoltaic current density-voltage (J-V) as a function of AOI in textured silicon solar cells with and without In NPs. We observed a reduction in optical reflectance and an increase in EQE when the cells textured with pyramidal structures were coated with In NPs. We also observed an impressive increase in the average weighted external quantum efficiency (∆EQEw) and short-circuit current-density (∆Jsc) in cells with In NPs when illuminated under a higher AOI. The ∆EQEw values of cells with In NPs were 0.37% higher than those without In NPs under an AOI of 0°, and 3.48% higher under an AOI of 75°. The ∆Jsc values of cells with In NPs were 0.50% higher than those without In NPs under an AOI of 0°, and 4.57% higher under an AOI of 75°. The application of In NPs clearly improved the light trapping effects. This can be attributed to the effects of plasmonic light-scattering over the entire wavelength range as well as an expanded angle of incident light.

In this work, a simple method of solution process to fabricate high density Silicon nanohole (SiNH) arrays on n-type wafer is experimented. SiNHs exhibit very low reflectance from range of wavelength 300 to 1100 nm irrespective of the angle of incidence, better than Si nanowires. The SiNH arrays have a strong light trapping effect between the nanostructures causes high absorption. We experimentally demonstrate high-efficiency organic-inorganic hybrid solar cells, Si/PEDOT:PSS with silicon nanoholes. Such Si/PEDOT:PSS hybrid solar cells exhibit high Jsc of 36.80 mA/cm2, Voc of 0.52V, FF of 66.50%, and thus power conversion efficiency (PCE) of 12.72%. SiNH arrays produce a large surface-area-to-volume ratio, hence allowing efficient light harvesting and charge collection via the formation of a core-sheath p-n junction.

In this work, we added Zonyl fluorosurfactant into poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to improve the affinity of PEDOT:PSS and silicon nanowire (SiNW) arrays. The concentration of Zonyl fluorosurfactant is 0%, 0.1%, 0.5%, 1%, and 10%. The 0.5%-Zonyl treated PEDOT:PSS/SiNW solar cell has the highest open-circuit voltage of 0.541 V, but the best efficiency is the device with 0.1%-Zonyl treated PEDOT:PSS. The efficiency is 9.18%.

This paper reports an organic–inorganic hybrid solar cell with a hierarchical surface composed of high density silicon nanoholes and micro-desert textures. High-efficiency organic–inorganic hybrid solar cell Si/PEDOT–PSS with a hierarchical surface, showing a power conversion efficiency of 12%. The structure provides excellent light absorption over 97% for the spectral range of 300 to 1100 nm with a thickness of 60 μm due to internal multiple reflections caused by subwavelength features of high density silicon nanoholes and micro-desert textures. In addition, from the angle of incidence (AOI) observed, even at the large angle of 75°, the reflectance value still exhibits less than 1%. With the advantage of very thin silicon material and inexpensive processing, hybrid silicon/polymer solar cells are promising for various applications and thus could be an economically feasible alternative energy solution in the future.

Si nanohole and nanowire/organic polymer solar cell is fabricated by low temperature and simple spin-coating method. The results show that the nanohole device performance is better than that of nanowire device. The Si nanohole device has higher external quantum efficiency in all wavelengths. The reason for the enhancement is analyzed from optical reflectance and the observation between Si nanohole and PEDOT:PSS interface. With nanohole structure, the short-circuit current density is increased from 22.1 to 26.9 mA/cm2 (22% increase), and the power conversion efficiency is enhanced from 7.4% to 8.0%. Nanohole structure is promising for high-efficiency Si/organic polymer solar cell.

Optical engineering of vertically-aligned silicon nanowires (SiNWs) by modifying their surface morphology and composition can reduce the surface reflectivity and sub-bandgap absorption, leading to improved performance in SiNW-based solar cells.

In this paper, the electrical properties of the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)/silicon nanowire hybrid solar cell have been analyzed and an optimized structure is proposed. In addition, the planar PEDOT:PSS/c-Si hybrid solar cell is also modeled for comparison. We first developed a simulation software which is capable of modeling organic/inorganic hybrid solar cells by including Gaussian shape density of states into Poisson and drift-diffusion solver to present the tail states and trap states in the organic material. Therefore, the model can handle carrier transport, generation, and recombination in both organic and inorganic materials. Our results show that at the applied voltage near open-circuit voltage (Voc), the recombination rate becomes much higher at the PEDOT:PSS/Si interface region, which limits the fill factor and Voc. Hence, a modified structure with a p-type amorphous silicon (a-Si) layer attached on the interface of Si layer and an n+-type Si layer inser...

In the past decades, Si has been the most important material for electronics. By exploiting this mature semiconductor fabrication technique, it is also highly desired to use Si for applications in other areas. Here we report the use of Si micro-structures for optical-communications and Si nano-structures for energy applications. Sub-micron Si waveguides is fabricated on Si substrates rather than SOI (silicon on insulator) substrate using laser reformation technique. This method helps solve the incompatible problem for the integration of optics and electronics on a single Si chip. The typical thickness of the oxide layer on the CMOS transistor layer is below 100nm which, however, creates excessive optical loss due to the light coupling into Si substrate. Besides, fabricating Si photonics on Si wafer is much cheaper than that on SOI wafer. The method is using high-power pulse laser to melt high-aspect ratio Si ridges. This creates a structure with wider upper portion and narrower lower portion, which can be further oxidized and forming waveguides. For energy applications, Si nanostructures are fabricated using the metal-assisted chemical etching (MacEtch) technique. Si nanostructures could greatly reduce the surface reflection to enhance light harvest. In addition, Si nanowires are further combined with organic materials to form hetero-junction solar cells using low-cost solution process. Furthermore, the Si nanostructures and MacEtch process are refined to form completely single-crystal Si thin film. Thus the material cost of Si solar cells can be potentially reduced to only 1/10 of current ones.

Silicon nanowire (SiNW) arrays are widespread applied on hybrid photovoltaic devices because SiNW arrays can substitute the pyramid texture and anti-reflection coating due to its strong light trapping. Also, SiNWs can be prepared through a cost-efficient process of metal-assisted chemical etching. However, though longer SiNW arrays have lower reflectance, the top of long SiNWs aggregate together to make junction synthesis difficult for SiNW/organic hybrid solar cell. To control and analyze the effect of SiNW array morphology on hybrid solar cells, here we change the metal deposition condition for metal-assisted chemical etching to obtain different SiNW array morphologies. The experiment was separated to two groups, by depositing metal, say, Ag, before etching (BE) or during etching (DE). For group BE, Ag was deposited on n-type Si (n-Si) wafers by thermal evaporation; then etched by H 2 O 2 and HF. For group DE, n-Si was etched by Ag + and HF directly. Ag was deposited on n-Si during etching process. Afterwards, residual Ag and SiO 2 were removed by HNO 3 and buffered HF, successively; then Ti and Ag were evaporated on the bottom of Si to be a cathode. Finally, SiNWs were stuck on the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) that was spincoated on the ITO coated glass to form SiNW/organic heterojunction. The results show that group BE has reflectance lower than that in group DE in solar spectrum. However, group BE has smaller power conversion efficiency (PCE) of 8.65% and short-circuit current density (J sc ) of 24.94 mA/cm 2 than group DE of PCE of 9.47% and J sc of 26.81 mA/cm 2 .

Thin-film crystalline photovoltaic (PV) cell is a trend for future PV with its potential to achieve low cost and high efficiency. Concerning material utilization efficiency, we propose a method with a fast manufacturing method of thin crystalline Si by chemical solution. To obtain the highest efficiency of material utilization, experiments with different H 2 O 2 /HF ratio are conducted, where related mechanisms are discussed. Moreover, large-area (87.7 mm2) thin film transferred to glass is demonstrated, and with embedded nanohole structure, lowest optical reflectance of 0.26% is measured. These characteristics show that the fabricated thin film has potential for large-area crystalline thin film PV.

In this work, we develop a technique to form vertically aligned silicon nanowire (SiNW) arrays without aggregation at the top by cost and energy efficient metal-assisted chemical wet etching. The SiNW/PEDOT:PSS heterojunction solar cells are also fabricated with nanowire length varying from 0.758 °m to 5.27 °m. The 0.758-°m-SiNW/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cell has the best power conversion efficiency of 8.65% and short circuit current density of 24.94 mA/cm2.

Crystalline Si photovoltaic modules still have high production cost due to significant consumption of the Si wafer. Reducing the large amount of Si material consumption is thus a critical issue. Here we deve lop a two-step metal-assisted etching technique for forming vertically-aligned Si nanohole thin films from bulk Si wafers. The formation of Si nanohole thin films includes a series of solution processes: deposition of Ag nanoparticles in an AgNO 3 / HF aqueous solution, formation of Si nanohole arrays at the first-step metal-assisted etching, and side etching of the roots of the nanohole structure at the second-step meta l-assisted etching. All th e processes can proceed at around room temperature. A Si nanohole thin film with an averag e hole-size of 100 nm and a thickness of 5 m-20 m was hence formed at the top of the wafer. Afterwards, the Si nanohole thin film was tran sferred onto alien substrates. The Si nanohole thin film has the crystal quality similar to the bulk Si wafer. The above bul k Si substrate can be reused. With similar processes, other Si nanohole thin films can be formed fr om the above recycled Si wafer. The hole size and thickness are similar. The Si wafers recycled will significan tly reduce the material consumption of Si. Thus, such technique is promising for lowering the cost of Si solar cells. Keywords: Si nanohole, metal-assisted etching, transfer, lithium battery anode, Si nanohole powder, photovoltaic, Si wafer recycling.

Ultra short silicon nanowires (SiNWs) were applied on Si/Poly(3,4-ethylenedioxy-thiophene): poly(styrenesulfonate) (PEDOT:PSS) solar cells by solution process. The short circuit current density (J sc ) is 23.72 mA/cm2, and power conversion efficiency (PCE) is 7.38%

Si nanostructures are promising materials for future photovoltaic applications. To date the Si nanostructures are mainly formed on particular substrates or at high temperatures, greatly limiting their application flexibility. Here we report a two-step metal-assisted etching technique for forming vertically aligned Si nanohole thin films on bulk Si wafers at room temperature. The Si nanohole thin films with a thickness of 5µm can be easily transferred to alien substrates. Because of the low temperature transfer process, it enables a large variety of alien substrates such as glass and plastics to be used. In addition, we demonstrate that the bulk Si substrate can be reused to fabricate Si nanohole thin films. The consumption of bulk Si materials is significantly reduced.

Silicon nanowire (SiNW)/Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cells were fabricated by solution process. The effect of nanowire length to cell performance was investigated for the nanowire length varying from 0.73 μm to 5.59 μm. The nanowire length was found to have negative effect on the power conversion efficiency (PCE), in the condition of the fixed thickness of PEDOTPSS. The highest PCE of 7.02% was obtained for the wire length of 0.73 μm.

Silicon nanowire (SiNW)/Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cells were fabricated by solution process. The nanowires of 370 nm were coated with PEDOT:PSS. The short circuit current density and power conversion efficiency are 27.46 mA/cm2 and 8.05%, respectively.

Si nanowires (SiNWs) are promising materials for future electronic, photovoltaic, and sensor applications. To date the SiNWs are mainly formed on particular substrates or at high temperatures, greatly limiting their application flexibility. Here we report a low temperature process for forming and massively transferring vertically aligned SiNWs on alien substrates. Metal-assisted etching method was used to fabricate vertically aligned SiNWs on Si substrates. To detach SiNWs from Si substrates, the roots of the Si NWs were etched and became fragile by controlling direction of metal-assisted etching. Thus, every SiNW on the Si substrate can be easily transferred to alien substrates. Because of the low temperature process, it enables a large variety of alien substrates such as glass and plastics to be used.

Silicon nanowire (SiNW)/Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) Schottky junctions have shown great promise as high efficiency, cost effective solar cells. Here, hybrid SiNWs/PEDOT:PSS blended graphene oxide (GO) solar cells are prepared and investigated. The SiNWs/PEDOT:PSS blended GO cells show enhanced light trapping and a large junction area when compared to pure PEDOT:PSS structures. SiNWs combined with GO solar cells show energy conversion efficiencies of up to 9.57% under the AM 1.5G condition, opening the possibility of using semiconductor/graphene oxide in photovoltaic applications.

Various Si nanostructures can be fabricated using a metal-assisted etching technique, which must be applied on bulk Si wafers, limiting its applications and wasting a significant amount of material. Here, we report a technique to form a Si nanostructured thin film created by metal-assisted chemical etching from bulk Si wafers and to transfer it onto alien substrates. To detach the Si nanostructured thin films completely from bulk Si wafers, a second-step metal-assisted chemical etching made the root of the Si nanostructures become fragile. The transferred Si nanostructures are well-aligned along the normal direction of the receiver substrate. The X-ray diffraction spectrum reveals that the transferred Si nanostructured thin films exhibit good crystal orientation and morphology. A strong light trapping effect between the nanostructures causes such films of 16 μm thickness to exhibit nearly 99% absorption from 400 to 800 nm. This exceeds the theoretically calculated limits of planar Si.

Photovoltaic performance of a thin-film silicon solar cell based on light-trapping enhanced and surface-recombination reduced using an optimization of metal-assisted chemical etching (MACE) and TiO2 passivation was demonstrated. The silver nanoparticles were used as etched mask in MACE process to obtain a nanoporous silicon surface layer. The optical reflectance, dark and photovoltaic current-voltage, external quantum efficiency as a function of the MACE times are measured and compared. Significant improving efficiency of 38% was obtained for the cell with 10-second MACE time and 15-nm-thick TiO2 passivation.