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Improving the performances and reducing costs of III-V multijunction solar cells are crucial in aerospatial energy systems and in terrestrial concentrator modules. We attempted to achieve both objectives by implementing non-ohmic metal/semiconductor interface contacts on the front surface of III-V/Ge triple-junction solar cells. We demonstrate the feasibility of this concept for this type of solar cell by a simple evaporation of Al only either on the GaAs contact layer or the AlInP window. The best results were obtained when sulfur passivation by (NH4)2Sx was conducted on the GaAs contact layer. This allowed for a reduction in reverse saturation dark current density by one order of magnitude and a slight increase in V o c of almost 20 mV under 1 sun illumination relative to a reference device with Pd/Ge/Ti/Pd ohmic contacts. However, poor performances were observed at first under concentrated sunlight. Further annealing the solar cells with Al front metallization resulted in the reduction of V o c to the same level as the reference solar cell but allowed for good performances under high illumination. Indeed, an efficiency over 34% was observed at 500 suns light intensity both for Al and Pd/Ge/Ti/Pd contacted solar cells. [ABSTRACT FROM AUTHOR]

Improving the performances and reducing costs of III-V multijunction solar cells are crucial in aerospatial energy systems and in terrestrial concentrator modules. We attempted to achieve both objectives by implementing non-ohmic metal/semiconductor interface contacts on the front surface of III-V/Ge triple-junction solar cells. We demonstrate the feasibility of this concept for this type of solar cell by a simple evaporation of Al only either on the GaAs contact layer or the AlInP window. The best results were obtained when sulfur passivation by (NH4)2Sx was conducted on the GaAs contact layer. This allowed for a reduction in reverse saturation dark current density by one order of magnitude and a slight increase in Voc of almost 20 mV under 1 sun illumination relative to a reference device with Pd/Ge/Ti/Pd ohmic contacts. However, poor performances were observed at first under concentrated sunlight. Further annealing the solar cells with Al front metallization resulted in the reduction of Voc to the same level as the reference solar cell but allowed for good performances under high illumination. Indeed, an efficiency over 34% was observed at 500 suns light intensity both for Al and Pd/Ge/Ti/Pd contacted solar cells.

Silicon Carbide (SiC) passivating contacts are thought to be an emerging solution to bridge the existing gap in the silicon-based solar market. Passivating contacts directly tackle the intrinsic metal-semiconductor interfaces issues like recombination losses and Fermi-level pinning. Considering this approach, SiC-based Transparent Passivating Contacts (TPC) are fabricated on n-Si <100> using RF magnetron sputtering at multiple RF powers for enhanced solar cell performance. All said contacts were convolved through a variety of optical, and electrical techniques. It is confirmed that the passivating contacts grown by higher RF power have an enhanced provision for both transmission and contact passivation. Additionally, it has been found that a sufficient amount of oxygen vacancies (V O) are located at the SiC/Si interface and are mainly responsible for limiting of the contact passivation. This issue might be resolved by opting for larger RF power during the SiC growth that may suppress V O impact. Further, purely optical and electro-optical parameters and their dependence on V O have been readily studied. Most importantly the extent of contact passivation has been readily measured by the transient of photo voltages and Q-DLTS techniques and cross-verified by current kinetics studies. It is found by the current-voltage and energy band picture that the SiC grown at higher RF would provide better contact passivation with surface resistance of ∼109 Ω and positive trap centers, respectively. • There are the following highlights which glance at the overall manifesto of this research article. • This work is focused on the fabrication and characterization of SiC-based passivation as well as transparent contacts for Solar Cell applications. • SiC layers were grown by RF Magnetron Sputtering at four different variable powers. • The extent of passivation and transparency of SiC layers have readily characterized using a variety of techniques i.e. Spectroscopic Ellipsometry, Photo-Luminescence, Charge Deep Level Transient Spectroscopy, and Transient of Photo Voltage and kinetics of dark and photocurrents. • It was determined that the SiC grew at a comparatively larger power and may provide a larger extent of both passivation and transparency. [ABSTRACT FROM AUTHOR]

TCAD simulations of a p-Si/Al 2 O 3 /Al structured solar cell are done to improve the understanding of parameters important for tunneling contact passivation. High efficiencies are achieved for oxide thicknesses below 1.4 nm and for an oxide interface charge concentration of -1×10 13 cm -3 . The dependence of the work function of Al is shown. The effective mass of bulk Al 2 O 3 is found to be too large for tunneling to occur, so a smaller effective mass is likely for thin films. The simulations of charges, work function, band gap and dielectric constant can also be used as a basis for choosing new tunneling materials. [ABSTRACT FROM AUTHOR]

We investigate passivation of the aluminum-silicon interface by thin aluminum oxide (Al 2 O 3 ) layers grown by thermal atomic layer deposition (ALD) on HF-last silicon surfaces. We first report effective lifetimes of Al 2 O 3 -passivated n- and p-type silicon wafers as a function of the number of ALD cycles. Then, we present saturation current density and contact resistance measurements of aluminum contacts on n/n + and n/p + junctions, passivated with a selection of the investigated layers. Our results show that aluminum contacts on n + silicon can be successfully passivated with thin Al 2 O 3 layers without compromising contact resistance. However, we did not observe significant contact passivation for acceptable contact resistance in the case of Al 2 O 3 passivated aluminum contacts on p + silicon. We explain our experimental results from the asymmetry between conductance and valence band offsets of Al 2 O 3 on silicon. [ABSTRACT FROM AUTHOR]

Abstract: The potential of contact passivation for increasing cell performance is indicated by several results reported in the literature. However, scant characterization of the tunneling layers used for that purpose has been reported. In this paper, contact passivation is investigated by insertion of an ultra-thin AlOx layer between an n-type emitter and a Ti/Pd/Ag contact. By using a 1.5nm thick layer, an increase of the minority carrier lifetime by a factor of 2.7 is achieved. Since current-voltage measurements indicate that an ohmic behavior is conserved for AlOx layers as thick as 1.5nm, a 1.5nm AlOx layer is found to be a candidate of choice for contact passivation. [Copyright &y& Elsevier]

Interface engineering is of great concern in photovoltaic devices. For the solution‐processed perovskite solar cells, the modification of the bottom surface of the perovskite layer is a challenge due to solvent incompatibility. Herein, a Cl‐containing tin‐based electron transport layer; SnOx‐Cl, is designed to realize an in situ, spontaneous ion‐exchange reaction at the interface of SnOx‐Cl/MAPbI3. The interfacial ion rearrangement not only effectively passivates the physical contact defects, but, at the same time, the diffusion of Cl ions in the perovskite film also causes longitudinal grain growth and further reduces the grain boundary density. As a result, an efficiency of 20.32% is achieved with an extremely high open‐circuit voltage of 1.19 V. This versatile design of the underlying carrier transport layer provides a new way to improve the performance of perovskite solar cells and other optoelectronic devices. [ABSTRACT FROM AUTHOR]