Interface carrier recombination currently hinders the performance of hybrid organic-silicon heterojunction solar cells for high-efficiency low-cost photovoltaics. Here, we introduce an intermediate 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) layer into hybrid heterojunction solar cells based on silicon nanowires (SiNWs) and conjugate polymer poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS). The highest power conversion efficiency reaches a record 13.01%, which is largely ascribed to the modified organic surface morphology and suppressed saturation current that boost the open-circuit voltage and fill factor. We show that the insertion of TAPC increases the minority carrier lifetime because of an energy offset at the heterojunction interface. Furthermore, X-ray photoemission spectroscopy reveals that TAPC can effectively block the strong oxidation reaction occurring between PEDOT:PSS and silicon, which improves the device characteristics and assurances for reliability. These learnings point toward future directions for versatile interface engineering techniques for the attainment of highly efficient hybrid photovoltaics.

Colloidal quantum dots which can emit red, green, and blue colors are incorporated with a micro-LED array to demonstrate a feasible choice for future display technology. The pitch of the micro-LED array is 40 μm, which is sufficient for high-resolution screen applications. The method that was used to spray the quantum dots in such tight space is called Aerosol Jet technology which uses atomizer and gas flow control to obtain uniform and controlled narrow spots. The ultra-violet LEDs are used in the array to excite the red, green and blue quantum dots on the top surface. To increase the utilization of the UV photons, a layer of distributed Bragg reflector was laid down on the device to reflect most of the leaked UV photons back to the quantum dot layers. With this mechanism, the enhanced luminous flux is 194% (blue), 173% (green) and 183% (red) more than that of the samples without the reflector. The luminous efficacy of radiation (LER) was measured under various currents and a value of 165 lm/Watt was recorded.

In this work, hybrid heterojunction solar cells are demonstrated based on a conjugate polymer poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) directly spun-cast on micro-textured n-type crystalline silicon wafers. The fabrication conditions suggest that the organic coverage on the micro-textured surface is excellent and key to achieve high efficiency, leading to an average power conversion efficiency of 9.84%. A one-dimensional drift-diffusion model is then developed based on fitting the device characteristics with experimentally determined PEDOT:PSS parameters and projects an ultimate efficiency above 20% for organic/inorganic hybrid photovoltaics. The simulation results reveal the impacts of defect densities, back surface recombination, doping concentration, and band alignment.

Global-warming issues coupled with high oil prices have become a major driving force for the use of advanced solar power technology, where a key component lies in the development of high-efficiency and low-cost photovoltaic cells. Next generation photovoltaics, hence, demand an efficiency-boosting mechanism in order to render solar energy cost competitive with conventional sources of electricity.[1] Fundamentally, the conversion efficiency of a solar cell depends on the photon absorption, carrier separation, and carrier collection. [2,3] Therefore, an effective antireflection (AR) coating, minimized recombination loss, and good Ohmic contacts are particularly important. Metal grids that inevitably block the transmission of solar energy also require optimization in order to reduce the series resistance. The trade-off between the electrode and the AR coating areas is one of the efficiency-limiting factors in a conventional solar cell.The conventional AR coating is usually composed of a quarter wavelength stack of dielectrics with different refractive indices. Broad angular and spectral AR is achievable at the price of multiple layers.[ [4][5][6][7] Over the past few years, versatile subwavelength structures (SWS) have emerged as promising candidates for AR coatings, due to the characteristics of zero-order gratings, or the so-called moth-eye effects. [8][9][10][11][12][13][14] However, the fabrication costs, which involve either electron-beam (e-beam) lithography or various etching processes, can be significant. In addition, the resulting surface-recombination loss due to dry or wet etching could further hinder the applications of SWS in commercial solar cells. Recently, multiple studies have been carried out on indium tin oxide (ITO), titanium dioxide (TiO 2 ), and silicon dioxide (SiO 2 ) nanostructures employing oblique-angle deposition methods, [15][16][17] where the refractive indices of the nanoporous materials can be engineered by adjusting the air volume ratio. Still, the materials require multiple layers to effectively suppress the Fresnel reflection.In this paper, we demonstrate a practical photovoltaic application of ITO nanocolumns serving as a conductive AR layer for GaAs solar cells. As in standard GaAs cells, the use of a nanostructured AR layer could be otherwise limited due to severe front-surface recombination. The characteristic ITO nanocolumns, prepared by glancing-angle deposition with an incident nitrogen flux, offer omnidirectional and broad-band AR properties for both s-and p-polarizations, up to an incidence angle of 708 for the 350-900 nm wavelength range. Calculations based on a rigorous coupled-wave analysis (RCWA) method indicate that the superior AR characteristics arise from the tapered column profiles, which collectively function as a graded-refractive-index layer. The conversion efficiency of the GaAs solar cell with the nanocolumn AR layer increases by 28% compared to a cell without any AR treatment. Moreover, nearly 42% enhancement is achieved for photocurrents generated at wavele...

High efficiency GaN-based light-emitting diodes ͑LEDs͒ are demonstrated by a nanoscale epitaxial lateral overgrowth ͑NELO͒ method on a SiO 2 nanorod-array patterned sapphire substrate ͑NAPSS͒. The transmission electron microscopy images suggest that the voids between SiO 2 nanorods and the stacking faults introduced during the NELO of GaN can effectively suppress the threading dislocation density. The output power and external quantum efficiency of the fabricated LED were enhanced by 52% and 56%, respectively, compared to those of a conventional LED. The improvements originated from both the enhanced light extraction assisted by the NAPSS and the reduced dislocation densities using the NELO method.

Hybrid organic-silicon heterojunction solar cells promise a significant reduction on fabrication costs by avoiding energy-intensive processes. However, their scalability remains challenging without a low-cost transparent electrode. In this work, we present solution-processed silver-nanowire meshes that uniformly cover the microtextured surface of hybrid heterojunction solar cells to enable efficient carrier collection for large device area. We systematically compare the characteristics and device performance with long and short nanowires with an average length/diameter of 30 μm/115 nm and 15 μm/45 nm, respectively, to those with silver metal grids. A remarkable power conversion efficiency of 10.1% is achieved with a device area of 1 × 1 cm 2 under 100 mW/cm 2 of AM1.5G illumination for the hybrid solar cells employing long wires, which represents an enhancement factor of up to 36.5% compared to the metal grid counterpart. The high-quality nanowire network displays an excellent spatial uniformity of photocurrent generation via distributed nanowire meshes and low dependence on efficient charge transport under a high lightinjection condition with increased device area. The capability of silver nanowires as flexible transparent electrodes presents a great opportunity to accelerate the mass deployment of high-efficiency hybrid silicon photovoltaics via simple and rapid soluble processes. KEYWORDS: silver nanowire, solution process, conductive polymer, photovoltaics P hotovoltaic technology is playing an increasingly important role in electricity generation because of rising concerns with petroleum scarcity and green-house gas emissions. Nowadays, crystalline-silicon photovoltaics have a dominant market share for their high efficiency, environmental friendliness, and abundant material supply. 1 However, their energy payback time is still much longer than other thin-film-based technologies, 2 which is largely ascribed to the wafer cost and energy-intensive fabrication processes, such as furnace diffusion (900°C), electrode cofiring (900°C), and high-vacuum chemical deposition (400°C). Consequently, hybrid organic/ silicon solar cells have become an attractive approach in which the device combines the advantages of rapid wet-chemical processes with organic materials and wide absorption range with silicon for the heterojunction formation. 3−7 Among the multiple emerging organic materials, hybrid solar cells based on conductive polymer poly(3,4-ethylenedioxy-thiophene):poly-(styrenesulfonate) (PEDOT:PSS) directly spun-cast on planar or nanostructured silicon surfaces exhibit the most promising performance with a power conversion efficiency (PCE) of approximately 10%. 8−12 A validated device model has further projected that an ultimate efficiency of over 20% is possible with the band alignment of PEDOT:PSS and silicon by controlling interface states, surface reflection, and other factors. 13 Nevertheless, efficient carrier collection presents one of the bottlenecks for the scalability of hybrid devices because of...

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Characteristic formation of highly oriented indium-tin-oxide (ITO) nanocolumns is demonstrated using electron-beam evaporation with an obliquely incident nitrogen flux. The nanocolumn material exhibits broadband and omnidirectional antireflective characteristics up to an incidence angle of 70° for the 350–900 nm wavelength range for both s- and p-polarizations. Calculations based on a rigorous coupled-wave analysis indicate that the superior antireflection arises from the tapered column profiles which collectively function as a gradient-index layer. Since the nanocolumns have a preferential growth direction which follows the incident vapor flux, the azimuthal and polarization dependence of reflectivities are also investigated. The single ITO nanocolumn layer can function as antireflection contacts for light emitting diodes and solar cells.