Search

High-energy electron-beam irradiation of indium gallium zinc oxide (IGZO) films improved the short-range arrangement. The increase in band gap was used as an indication of such improvement. X-ray diffraction confirmed that the films treated with a DC voltage of 2–4.5 kV for duration of up to 35 min are in the amorphous state or nanocrystalline phase. Higher energy electron-beam irradiation led to increased conductivity, which mainly comes from the drastic increase in electron concentration. Electron-beam treatment could be a viable route to improve the contact resistance between the source/drain and channel layer in thin-film transistor devices.

In this study, a cost effective and low temperature approach to fabricate a shallow-emitter crystalline silicon (c-Si) solar cell using a low sheet resistance, and highly transparent indium tin oxide (ITO) as an antireflection layer is presented. Deposited films with either (400) or (222) predominant planes were obtained by varying the substrate temperature. Better crystallization, good electrical properties, higher optical gap, and higher work function were observed for the films with (400) predominant planes; however, the transmittance in the near-infrared region suffered from free-carrier absorption effect. These ITO films were applied to replace the conventional SiNx film, as an antireflection coating for a c-Si solar cell with shallow-emitter having a sheet resistance of 100 Ω/⎕. Using the optimal condition, the photovoltaic parameter of the device yielded an open-circuit voltage and fill factor of up to 604 mV and 81.59%, respectively, resulting in an efficiency of 17.27%. This photovoltaic conversion efficiency, based on the c-Si solar cell with shallow-emitter, is relatively higher than that of the current reports.

Transparent conductive zinc oxide (ZnO) thin films were synthesized by a sol–gel spin coating method with the addition of Ga(NO 3 ) 3 in a Zn(CH 3 COO) 2 solution and exposed to electron beam treatment. The UV–Vis spectra demonstrated that all of the films had transmittances of over 85% in the visible region. When Ga(NO 3 ) 3 was added to the ZnO precursor solution, the resistivity of the ZnO thin film decreased and the carrier concentration increased significantly. After electron beam treatment was performed on the 0.4 at.% Ga-doped ZnO film, the optical band gap increased and the resistivity significantly decreased resulting from the increases of the carrier concentration and mobility. By combining Ga doping and electron beam treatment, the resistivity of the ZnO thin film was reduced by a factor of nine hundred.

An electron-beam annealing method has been adapted for rapid crystallization of p-type amorphous-silicon thin films deposited by using an evaporation method. The amorphous phase of silicon thin-film was crystallized by using an accelerating DC voltage higher than the 4.0 kV for 120 s. From the crystalline properties, the nanocrystalline silicon thin film after electron-beam annealing showed mainly (111), (220), and (311) orientations and a crystalline volume fraction (Xc) of 93.6%. The crystalline properties improved with increasing DC voltage for rapid annealing times. The electron-beam annealing method can be a powerful method for achieving rapid crystallization of amorphous materials.

CuInSe2 (CIS) films on Mo/soda-lime glass were prepared by selenization of sputtered precursors from Cu2Se and In2Se3 binary targets. Cu–In–Se precursors were sequentially sputtered with double-layered structure of both Cu2Se/In2Se3 and In2Se3/Cu2Se. The structural, compositional and electrical properties of annealed Cu–In–Se precursors were investigated for solar cell applications. Better adhesion between CIS and Mo back contact was observed in the double-layered structure of Cu2Se/In2Se3 at all working pressures. Less MoSe2 phase on both structures was generated at a lower working pressure of 0.67 Pa. A CIS solar cell with Al/Al-doped ZnO/i-ZnO/CdS/CIS (900 nm, Cu2Se/In2Se3 at 0.67 Pa)/Mo/soda-lime glass was continuously fabricated, and its conversion efficiency was 4.6%, with 346 mV of open circuit voltage, 30.5 mA/cm2 of short circuit current density and 43.5% fill factor.

Undoped and Al-doped ZnO thin films were prepared by a sol–gel spin coating method. The films were exposed to the electron beam at different energies to improve their electrical properties by modifying their film crystallinity. For both the undoped and Al-doped ZnO thin films, the carrier concentration significantly increased and the resistivity decreased after the introduction of the energetic electron beam. Since band gap widening of the undoped and Al-doped ZnO thin films was also observed with exposure to the electron beam, the behaviors and tendencies can be explained by the Burstein–Moss effect. The effects of the electron beam on ZnO thin film properties, including band gap widening, increasing carrier concentration, and significantly decreased resistivity, were similar to the effects of Al doping in ZnO. Finally, by combining electron beam treatment and Al doping of ZnO thin films prepared by a sol–gel method, the resistivity of the sol–gel synthesized ZnO thin film decreased from 5.8 × 10 2 Ω cm to 8.2 × 10 − 2 Ω cm. According to the Monte Carlo simulation of electron penetration in the ZnO thin film, the penetration depth increased with electron beam energy, which induced lattice heating and atomic rearrangement by electronic excitation in a collision cascade.

Intrinsic ZnO (i-ZnO) thin films were prepared using radio frequency (RF) sputtering method with working pressure range of 1-20 mTorr and treated by electron beam (e-beam) irradiation unit with 300 W of RF power and 2.5 kV of DC power for 5 min. As working pressure increased to 20 mTorr, deposition rate of samples gradually decreased from 0.3 angstroms/sec to 0.18 angstroms/sec and grain size from 23.6 nm to 16.0 nm. After e-beam treatment on RF sputtered i-ZnO thin films with increasing of working pressure, thickness were totally declined by 10% and grain sizes were grown bigger. The electrical properties of e-beam treated samples were remarkably improved to be - 10(18) cm(-3) of carrier concentration, 2-7 cm2/Vs of Hall mobility and - 10(-1) omega x cm of resistivity. Transmittance of e-beam treated samples were up to -90% and optical bandgap increased to 3.27-3.31 eV, resulted from decline of thickness. The better properties of ZnO thin films as a buffer layer in thin film solar cells could be obtained by e-beam treatment method.

Molybdenum (Mo) has been used as back contact layer in chalcopyrite solar cells family (CulnSe2 and its alloys) because it showed the excellence of electrical properties such as low resistivity at the Mo interference. Generally, there are strong corrleations between working pressure and properites such as adhesion and conductivity during deposition of Mo layer. Electrical properites might be inversely proportional to adehsion between Mo layer and glass substrate. Several methods have been executed for improvement of electrical properties and ahesion. In this study, DC sputtered Mo back contact layers on sodalime glass were prepared with working pressure range of 1-10 mTorr, and then all samples were treated by rounded exposure of electron beam at DC power of 3 kV for 5 minutes. After electron-beam treatement, all samples showed the lower resisitivity and sheet resisitance than as-deposited Mo layers. As working pressure decreased, grain size of e-beam treated samples gradually increased up to 30.7 nm. E-beam treated Mo layer might be a good candidate as back contact layer of tandem structured CIS families thin film solar cells.

Cu–In–Se double-layered precursors were prepared using DC- and RF-sputtering methods and then irradiated with an in-situ electron beam irradiation unit. The irradiation time, electron dose and intensity were kept constant at 300 s, 200 W of RF power and 2.5 kV of DC power, respectively. The thicknesses of all e-beam irradiated CuInSe2 films were decreased from 850 nm to 700 nm and better adhesion between interfaces was observed in the Cu2Se/In2Se3 structure. The crystalline properties of e-beam irradiated CuInSe2 films were clearly shown in the In2Se3/Cu2Se structure formed at 5 mTorr with the Se/(Cu+In) composition ratios of 1.24 and 1.22, applicable to the solar cell. A CuInSe2 solar cell was fabricated, and its conversion efficiency was 6.82%, with 390 mV of open circuit voltage, 32.3 mA/cm2 of short circuit current density and 54% fill factor. E-beam irradiation onto Cu–In–Se precursors could be a good candidate for preparation of CuInSe2 films.

Chalcopyrite Cu(In,Ga)(Se,S)

We used a DC-sputtering method to deposit the precursor (Cu3Ga/In) onto Mo with 1 um thick/soda-lime glass (SLG). We moved it onto a graphite crucible for the pre-annealing process, and the pressure of the process tube was about 10 torr without Ar gas flow. The crucible in quartz tube was heated by halogen lamp to 250 degrees C for 30 min, and then raised to 550 degrees C for 10 min under a selenium atmosphere. To complete the solar cells, a buffer layer of 50 nm CdS was then deposited by chemical bath deposition (CBD), followed by a double layer (high resistivity/low resistivity) of RF sputtered i-ZnO/Al-ZnO thin films. The Al front contacts were deposited by thermal evaporator.

Cu-In-Ga-Se precursors were prepared by RF- and DC-sputtering methods and then irradiated with an in-situ electron beam irradiation unit. Ternary (In,Ga)Se2 and binary CuSe targets were simultaneously used for preparation of precursors. The electron dose and irradiation time were kept constant at 300 seconds and 200 W of RF power, respectively, while intensities of accelerated electrons were varied from 2.5 to 4.5 keV. The thickness of all e-beam irradiated CuInGaSe2 (CIGS) films decreased from 1,250 nm to 470 nm. The crystalline properties of e-beam irradiated CIGS films were clearly shown on all samples and the highest intensity of (112) peak at 3.5 keV. The compositional ratio of Cu/(In + Ga) in the e-beam sample irradiated at 3.5 keV was coincident with that of the precursors. The degree of Ga content on the depth of the e-beam sample irradiated at 3.5 keV was uniformly distributed between the TCO/CdS layer and Mo back contact. Electron beam irradiation onto Cu-In-Ga-Se precursors as a rapid annealing method could be an excellent candidate for crystallization to the Cu(In,Ga)Se2 films.

ZnO diffusion barrier layer was deposited by RF magnetron sputtering by using the same method as intrinsic ZnO layer. The CIGS solar cells were fabricated on stainless steel substrate. The 50-200 nm thin ZnO diffusion barriers effectively reduced the diffusion of Fe and Cr, from stainless steel substrates into the CIGS absorbers. The CIGS solar cells with ZnO diffusion barriers increased the J(sc) and FF, which resulted in an increase of cell efficiency from 5.9% up to 9.06%.

The silicon (Si) microwires were fabricated by microsphere lithography using polystyrene (PS) beads monolayer. The Si wafer tailored into 40 x 40 mm2 was used as a substrate. The monolayer of 2.0 μm-sized PS beads was formed on substrates through convective assembly method. PS beads on substrates were tailored into smaller sizes by O2 plasma treatment using reactive ion etching (RIE). This controllable re-sizing process gave an opportunity to prepare the wire-array with various radii of Si microwires fabricated by using inductively coupled plasma (ICP)-etching. The convective assembly process was monitored in real-time through an optical microscope with a CCD camera. PS beads and structures of Si microwires were characterized using a scanning electron microscope (SEM) and the optical property was measured by the UV-Vis spectroscopy.

Cu-In-Se thin precursors were prepared by using the DC co-sputtering method and were then irradiated using an in-situ electron beam (e-beam) irradiation unit, which was equipped with a co-sputtering chamber. The irradiation time of the samples was varied from 0 sec to 300 sec, and the electron dose and intensity were kept constant with 200 W of RF power and 2.5 kV of DC power. As the irradiation time was increased to 300 sec, the grain size gradually increased with a few voids, and the XRD patterns showed several polycrystalline peaks of CuInSe2 (CIS). Also, the Raman crystalline peak at 173 cm−1 indicated excellent crystallinity of the CIS single phase, with a greater improvement and sharpness shown at higher irradiation times. The compositional ratio of Cu:In:Se after e-beam irradiation remained almost the same as that of the DC co-sputtered precursors. As the irradiation time was increased to 300 sec, the Hall mobility, resistivity, and carrier concentration were 0.14 cm2/Vs, 2.16 × 10−4 Ωcm, and 7 × 1022 cm−3, respectively. E-beam irradiation without the addition of selenium might be a good candidate as a rapid crystallization and annealing method for making Cu-In-Se precursors for the preparation of CIS absorber materials.

High-quality CuInSe 2 films with various Cu/In ratios were fabricated using hybrid sputtering and evaporation techniques. The Cu/In ratio was found to affect the structural and electrical properties of CuInSe 2 films, resulting in a change in the conversion efficiency of CuInSe 2 solar cells. CuInSe 2 films with various Cu/In ratios were characterized by scanning electron microscopy (SEM), Hall effect measurements and X-ray diffraction (XRD). The lowest pit density was observed on the surface of CuInSe 2 films with Cu/In ratio of 0.87. The CuInSe 2 films are composed of two layers with large and small grains at the top and bottom, respectively. XRD revealed the surface of the CuInSe 2 films to have a preferred orientation of (1 1 2) planes. The XRD intensity and full width at half maximum of the (1 1 2) plane of CuInSe 2 varied according to the Cu/In ratio. The mobility estimated form the Hall effects revealed large changes in CuInSe 2 films according to the Cu/In ratio.

The polycrystalline silicon (poly-Si) thin films were prepared by aluminum induced crystallization. Aluminum (Al) and amorphous silicon (a-Si) layers were deposited using DC sputtering and plasma enhanced chemical vapor deposition method, respectively. For the whole process Al properties of bi-layers can be one of the important factors. In this paper we investigated the structural and electrical properties of poly-crystalline Si thin films with a variation of Al thickness through simple annealing process. All samples showed the polycrystalline phase corresponding to (111), (311) and (400) orientation. Process time, defined as the time required to reach 95% of crystalline fraction, was within 60 min and Al(200 nm)/a-Si(400 nm) structure of bi-layer showed the fast response for the poly-Si films. The conditions with a variation of Al thickness were executed in preparing the continuous poly-Si films for solar cell application.

In this study, tunneling mechanisms controlling the a-Si:H thin film/c-Si tandem solar cell were investigated employing numerical simulation. First, the effect of doped nc-Si:H tunnel recombination junction (TRJ) was studied with different structures. The band diagram, electric field, and recombination rate characteristics were investigated under a dark condition with doped nc-Si:H TRJ. The trap-assisted model and field-dependent tunneling were used to model the recombination and transport influence of the valence band offset (ΔEV) between the p-type layer of the top cell and TRJ in the high field region. Simulation results showed that the highest efficiency of 23.98% (Short circuit current density, Jsc = 18.74 mA cm−2, open circuit voltage, Voc = 1.565 V, fill factor, FF = 81.76%) could be obtained in the case of n/p nc-Si:H TRJ.

Hydrogenated amorphous silicon carbide (a-SiC:H) film has been widely used as an emitter p layer in solar cells. For the better p layer, wide optical bandgap, and high electrical conductivity should be obtained from the effective method. We prepared the boron-doped a-SiC:H thin films using inductively coupled plasma chemical vapor deposition (ICP-CVD) method and characteristics on the small-area (2 cm x 2 cm) as well as the large-area films (diameter of 100 mm) were shown on it. As a substrate, the n-type (100) oriented CZ c-Si (5.5 approximately 6.5 omega x cm, 650 microm) wafers were used and cleaned by using the reduced RCA method. A silane (SiH4) of 99.999% purity, H2 and 60% hydrogen diluted ethylene (C2H4) was used as source gas for the deposition of intrinsic a-SiC:H films, and then diborane (B2H6), as the doping gas, is added to C2H4 and SiH4/H2 during the deposition of films. The uniformity of thickness and optical bandgap from large-area as-dep. films was at 1.8% and 0.3%, respectively. Heterojunction solar cell with 2 wt%-AZO/p-a-SiC:H/i-a-Si:H/c-Si/Ag structure was fabricated and characterized with diameter of 152.3 mm in this large-area ICP-CVD system. Conversion efficiency of 9.123% was achieved with a practical area of 100 mm x 100 mm, which can show the potentials to the fabrication of the large-area solar cell using ICP-CVD method.

Effective incident light should be controlled for improving the current density of solar cells by employing nano- and micro-structures on silicon surface. The elastomeric stamp process, which is more cost effective and simpler than conventional photolithography, was proposed for the fabrication of nano- and micro-structures. Polydimethylsiloxane (PDMS) was poured on a mother pattern with a diameter of 6 μm and a spacing of 2 μm; then, curing was performed to create a PDMS mold. The regular micropattern was stamped on a low-viscosity resin-coated silicon surface, followed by the simple reactive ion etching process. Nano-structures were formed using the Ag-based electroless etching process. As etching time was increased to 6 min, reflectance decreased to 4.53% and current density improved from 22.35 to 34.72 mA/cm2.

The CO2 gas sensor, based on the principle of electro-chemistry, was fabricated using the solid-electrolyte Li3PO4 film formed by a thermal evaporator and its sensing performances were studied. Thermal evaporated film was prepared with power of 10A, a working pressure of 10−6 mTorr and thickness of 1.2 µm. Then, it was annealed at 800 °C for 2h in air. Li2TiO3+TiO2 and Li2CO3 film were prepared using a screen printing method as the reference and the sensing electrode, respectively. Li3PO4 film showed a much denser structure than bulk-type Li3PO4 in SEM images. The response and recovery characteristics were very good at the higher CO2 concentration and its value was 280 mV and changed to 260 mV in the higher CO2 environment. It was also observed that the sensitivity decreased by 98 % when the CO2 concentration increased from 250 ppm to 5000 ppm. Response time and recovery time were measured to be 5 s and 7 s, respectively. These results showed enough potential for developing a CO2 gas sensor using Li3PO4 film instead of the bulk-type.

Intrinsic and phosphorus-doped hydrogenated microcrystalline silicon (microc-Si:H) films were prepared using inductively coupled plasma chemical vapor deposition (ICP-CVD) method. Structural, electrical and optical properties of these films were studied as a function of silane concentration, ICP source power and PH3/SiH4 gas ratio. Characterization of these films from Raman spectroscopy and X-ray diffraction revealed that the conductive film exists in microcrystalline phase embedded in an amorphous network. The condition of electrical properties (sigma(d): approximately 10(-7) S/cm, sigma(ph): approximately 10(-4) S/cm) and activation energy (0.55 eV), satisfied with properties of intrinsic microc-Si:H, was obtained at 1200 W of ICP power and 2% of silane concentration, respectively. At PH3/SiH4 gas ratio of 0.09%, dark conductivity has a maximum value of approximately 18.5 S/cm and optical bandgap also a maximum value of approximately 2.39 eV. The deposition rate was not satisfactory (4.9 angstroms/s) at same condition.

Intrinsic a-Si:H thin films, which can have passivation functions on the surface of crystalline Si, were deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD). The properties of the films were investigated at deposition temperatures ranging from 50 to 400 °C. The Si—H stretching mode at 2000 cm−1, which indicates good film quality, was found in the range of 150∼400 °C, but the film quality was not good at deposition temperatures below 150 °C. The passviation quality was determined by measuring the effective carrier lifetime using the quasi-steady state photoconductance (QSS-PC) technique. Two, 5, 7.5 and 10 nm thick films were deposited at 150 °C and annealed at 200 °C for 1 hour. The carrier lifetime of these films was approximately 3 times higher than that observed before annealing. A p a-SiC:H/i a-Si:H/n c-Si hetero-structure solar cell with a 7.8% efficiency and approximately 85% quantum efficiency (QE) was obtained by inserting an intrinsic a-Si:H thin film (5 nm) between the interfaces. These results highlight the potential applications of a passivation layer to heterojunction solar cells.

We investigated for comparison of large-area i-a-Si:H and p-a-SiC:H film quality like thickness uniformity, optical bandgap and surface roughness using both ICP-CVD and PECVD on the large-area substrate(diameter of 100 mm). As a whole, films using ICP-CVD could be achieved much uniform thickness and bandgap of that using PECVD. For i-a-Si:H films, its uniformity of thickness and optical bandgap were 2.8 % and 0.38 %, respectively. Also, thickness and optical bandgap of p-a-SiC:H films using ICP-CVD could be obtained at 1.8 % and 0.3 %, respectively. In case of surface roughness, average surface roughness (below 5 nm) of ICP-CVD film could be much better than that (below 30 nm) of PECVD film. HIT solar cell with 2 wt%-AZO/p-a-SiC:H/i-a-Si:H/c-Si/Ag structure was fabricated and characterized with diameter of 152.3 mm in this large-area ICP-CVD system. Conversion efficiency of 9.123 % was achieved with a practical area of , which can show the potential to fabrication of the large-area solar cell using ICP-CVD method.

The hydrogenated amorphous silicon (a-Si:H) films, which can be used as the passivation or absorption layer of solar cells, were prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD) and their characteristics were studied. Deposition process of a-Si:H films was performed by varying the parameters, gas ratio (H2/SiH4), radio frequency (RF) power and substrate temperature, while a working pressure was fixed at 70 m Torr. Their characteristics were studied by measuring thickness, optical bandgap (eV), photosensitivity, bond structure and surface roughness. When the RF power and substrate temperature were 300 watt and 200 °C, respectively, optical bandgap and photosensitivity, similar to the intrinsic a-Si:H film, were obtained. The Si-H stretching mode at 2000 cm−1, which means a good quality of films, was found at all conditions. Although the RF power increased up to 400 watt, average of surface roughness got better, compared to a-Si:H films deposited by the conventional PECVD method. These results show the potential for developing the solar cells using ICP-CVD, which have the relatively less damage of plasma.

Optical fibers containing gold metal nanoparticles were developed by modified chemical vapor deposition, in which Au(OH)3 and tetraethyl-orthosilicate (TEOS) was used via sol–gel process to incorporate gold metals by providing the reduction atmosphere. The absorption peak appeared near 490 nm was found to be due to the surface plasmon resonance of the gold nanoparticles incorporated in the fiber core.

An optical oxygen gas sensor, based on the principle of luminescence quenching by oxygen, was fabricated using a planar optical waveguide formed by ion exchanging method and its sensing performances were studied. Ion exchanging process was performed by substituting Ag + for Na + by immersing a patterned, 8 μm in size, phosphate glass into a jig for 20 min at 250 °C. Platinum octaethylporphyrin (PtOEP), selected as an oxygen quenchable material, was partially coated on the planar optical waveguide coupled to a single mode optical fiber, and then it was placed in a sensing cell. The sensing performances of the sensor were studied by measuring the photoluminescence intensity of PtOEP excited by a green laser beam (532 nm). It was observed that the photoluminescence intensity decreases as the oxygen concentration increases. The Stern–Volmer plot of the sensor shows linearity in the oxygen concentration range between 0 and 20%. Response time and recovery time were measured to be 100 and 80 s, respectively. These results show the potential for developing an optical oxygen gas sensor using a planar optical waveguide.

Al-doped ZnO (AZO) films were deposited onto glass substrates by RF magnetron sputtering for solar cell applications. The effects of the Al2O3 doping concentration on the structural, electrical, and optical properties of the AZO films were investigated. As the Al2O3 doping concentration was increased to 4.0 wt %, X-ray diffraction (XRD) showed a deterioration in the (002) peak intensity and a shift towards a higher angle. The best electrical properties (ρ= 9.8×10-4 Ω cm, µH = 22 cm2 V-1 s-1, and ne = 2.89×1020 cm-3) were obtained in the AZO sample containing 2 wt % Al2O3. Optical transmission >83% in the visible range was also observed and the optical bandgap was increased to 3.63 eV at an Al2O3 concentration of 4 wt %. For photoluminescence (PL) spectra, one UV emission peak at approximately 3.2 eV and a broad peak in the visible range from 2.3 to 2.7 eV were observed at Al2O3 doping concentrations ranging from 0–2.0 wt %. Blue emission at 2.67 eV, which indicates a non-stoichiometric structure, was only observed in the 4 wt % doped AZO films.

In this paper, we present a detailed study on the local back contact (LBC) formation of rear-surface-passivated silicon solar cells, where both the LBC opening and metallization are realized by one-step alloying of a dot of fine pattern screen-printed aluminum paste with the silicon substrate. Based on energy dispersive spectrometer (EDS) and scanning electron microscopy (SEM) characterizations, we suggest that the aluminum distribution and the silicon concentration determine the local-back-surface-field (Al-p+) layer thickness, resistivity of the Al-p+ and hence the quality of the Al-p+ formation. The highest penetration of silicon concentration of 78.17% in aluminum resulted in the formation of a 5 microm-deep Al-p+ layer, and the minimum LBC resistivity of 0.92 x 10-6 omega cm2. The degradation of the rear-surface passivation due to high temperature of the LBC formation process can be fully recovered by forming gas annealing (FGA) at temperature and hydrogen content of 450 degrees C and 15%, respectively. The application of the optimized LBC of rear-surface-passivated by a dot of fine pattern screen(-) printed aluminum paste resulted in efficiency of up to 19.98% for the p-type czochralski (CZ) silicon wafers with 10.24 cm2 cell size at 649 mV open circuit voltage. By FGA for rear-surface passivation recovery, efficiencies up to 20.35% with a V(OC) of 662 mV, FF of 82%, and J(SC) of 37.5 mA/cm2 were demonstrated.

We present a large-scale applicable nanolens-embedding solar cell. An electrically conductive and optically transparent indium-tin-oxide (ITO) thin film was coated on a Si substrate. After then, periodically patterned ITO nanodome-arrays were formed on the ITO film by using a nano-imprint method. This structure is effective to reduce the incident light reflection for broad wavelengths and also efficient to drive the incident photons into a light-absorbing Si substrate. There exist two electric fields. One is by a p/n junction and the other is by the light absorption into Si. We designed nanolens structures to overlap two electric fields and demonstrate highly improved solar cell performances of current and voltage values from a planar structure.

For effective light harvesting, a design weighting should be implemented in a front geometry, in which the incident light transmits from a surface into a light-active layer. We designed a three-dimensionally patterned transparent conductor layer for effective light management. A transparent conductive oxide (TCO) film was formed as three-dimensional structures. This efficiently drives the incident light at the front surface into a Si absorber to yield a reduction in reflection and an enhancement of current. This indicates that an optimum architecture for a front TCO surface will provide an effective way for light management in solar cells.