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Results for “double-junction”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

On the design and performance of InGaN/Si double-junction photocathodes

Via a combined theoretical and experimental study, we have investigated the synthesis and performance characteristics of InGaN/Si double-junction photoelectrochemical (PEC) water splitting devices, which promise a theoretical solar-to-hydrogen conversion efficiency ~30% under AM 1.5G one-sun illumination. The double-junction photocathodes consist of a p + -InGaN top light absorber and a Si bottom p-n junction, which are connected through a nanowire tunnel junction. The effect of indium composition of the top light absorber as well as the impact of p-type Mg dopant incorporation on the PEC performance was studied. Experimentally, the sample with 32% indium composition showed a maximum photocurrent density of ~9 mA/cm 2 at 0.4 mV vs reverse hydrogen electrode (RHE) with applied bias photon-to-current efficiency (ABPE) of ~9.5%. An optimum p-type doping level ~1 × 10 17 cm -3 was also identified, which results in the best device performance as a result of optimum surface band bending as well as vertical charge carrier (hole) transport. These results also show a good agreement with our theoretical analysis. This work provides significant insights in advancing the design and development of high efficiency PEC devices for artificial photosynthesis using industry ready materials, e.g., Si and GaN, to achieve large-scale, low-cost onsite hydrogen fuel production.

42 ENGINEERING↗
DOE OSTI2020

Demonstrating the GaInP/GaAs Three-Terminal Heterojunction Bipolar Transistor Solar Cell

The three-terminal heterojunction bipolar transistor solar cell (HBTSC) concept enables the realization of a monolithic double-junction device with individual current extraction. We present an HBTSC realized by a heterojunction of GaInP and GaAs. The one-sun open-circuit voltage (V OC ) of the top and bottom junctions are 1.33 V and 0.99 V, respectively, while fill factors (FF) are above 80%. At one-sun illumination, reducing one junction's bias from V OC to maximum power point degrades the performance of the other junction only slightly (<; 0.5% efficiency loss). These results demonstrate the potential of the HBTSC concept to produce high-efficiency independently connected double-junction solar cells.

14 SOLAR ENERGY↗
DOE OSTI2022

Progress in three-terminal heterojunction bipolar transistor solar cells

Conventional solar cells, including multijunction solar cells, are based on pn junctions as building blocks. In contrast, the three-terminal heterojunction bipolar transistor solar cell (3T-HBTSC) explores the use of a bipolar transistor structure to build a solar cell. The limiting efficiency of this transistor structure equals that of a double-junction solar cell. However, since the 3T-HBTSC does not require tunnel junctions, its minimal structure has only three semiconductor layers, while the minimal structure of a double junction solar cell has six. This work reviews the operation principles of this solar cell and the steps carried out towards its practical implementation. Experimental results on a GaInP/GaAs HBTSC prototype with bottom interdigitated contacts are presented.

14 SOLAR ENERGY↗
DOE OSTI2021

Compensated Contacts for Three-Terminal Transistor Solar Cells

The heterojunction bipolar transistor solar cell (HBTSC) is an alternative to conventional double-junction solar cells that combines the advantages of three-terminal architectures with a compact design. A critical part of the HBTSC fabrication is the implementation of the middle contact, the one associated to the base layer in the transistor structure, because this layer can be damaged by the diffusion of metallic species during contact annealing. As a solution we propose to implement a "compensated contact", that is, to leave a thin (< 200 nm) portion of emitter or collector between the base layer and the contact metals and compensate its doping during contact annealing. Using an Au/Zn/Au metal structure to compensate a 150 nm thick portion of the collector, we obtain a specific contact resistance ~8 10-4 ..omega.. cm2. This value is fairly invariant for annealing temperatures between 400 and 460 degrees C and annealing times between 2 and 5 minutes, and it does not improve by adding Pd to the metallic stack. Optimizing the compensated contact technology opens the path to the realization of III-V-material-based HBTSCs with open-circuit voltages and fill factors comparable to those of conventional multijunction architectures.

contact resistance↗
NASA NTRS1973

Residual water bactericide monitor development program

A silver-ion bactericidal monitor is considered for the Space Shuttle Potable Water System. Potentiometric measurement using an ion-selective electrode is concluded to be the most feasible of available techniques. Four commercially available electrodes and a specially designed, solid-state, silver-sulfide electrode were evaluated for their response characteristics and suitability for space use. The configuration of the solid-state electrode with its Nernstian response of 10 to 10,000 ppb silver shows promise for use in space. A pressurized double-junction reference electrode with a quartz-fiber junction and a replaceable bellows electrolyte reservoir was designed verification-tested, and paired with a solid-state silver-sulfide electrode in a test fixture.

Source record↗
NASA NTRS1974

Preliminary flight prototype silver ion monitoring system

The design, fabrication, and testing of a preliminary flight prototype silver ion monitoring system based on potentiometric principles and utilizing a solid-state silver sulfide electrode paired with a pressurized double-junction reference electrode housing a replaceable electrolyte reservoir is described. The design provides automatic electronic calibration utilizing saturated silver bromide solution as a silver ion standard. The problem of loss of silver ion from recirculating fluid, its cause, and corrective procedures are reported. The instability of the silver sulfide electrode is discussed as well as difficulties met in implementing the autocalibration procedure.

Brady, J.↗
NASA NTRS1988

Molecular-Beam-Epitaxy Program

Molecular Beam Epitaxy (MBE) computer program developed to aid in design of single- and double-junction cascade cells made of silicon. Cascade cell has efficiency 1 or 2 percent higher than single cell, with twice the open-circuit voltage. Input parameters include doping density, diffusion lengths, thicknesses of regions, solar spectrum, absorption coefficients of silicon (data included for 101 wavelengths), and surface recombination velocities. Results include maximum power, short-circuit current, and open-circuit voltage. Program written in FORTRAN IV.

Sparks, Patricia D.↗
DOE OSTI2021

Solar cell comprising an oxide-nanoparticle buffer layer and method of fabrication

A buffer layer for protecting an organic layer during high-energy deposition of an electrically conductive layer is disclosed. Buffer layers in accordance with the present invention are particularly well suited for use in perovskite-based single-junction solar cells and double-junction solar cell structures that include at least one perovskite-based absorbing layer. In some embodiments, the buffer layer comprises a layer of oxide-based nanoparticles that is formed using solution-state processing, in which a solution comprising the nanoparticles and a volatile solvent is spin coated onto a structure that includes the organic layer. The solvent is subsequently removed in a low-temperature process that does not degrade the organic layer.

Bush, Kevin Alexander↗
DOE OSTI2021

Inverted GaInP/GaAs Three-Terminal Heterojunction Bipolar Transistor Solar Cell

Here we present the experimental results of an inverted three-terminal heterojunction bipolar transistor solar cell (HBTSC) made of GaInP/GaAs. The inverted growth and processing enables contacting the intermediate layer from the bottom, which increases the cell performance by reducing shadow factor and series resistance at the same time. With this prototype we show that an inverted processing of a three-terminal solar cell is feasible and pave the way for the application of epitaxial lift-off, substrate reuse and mechanical stacking to the HBTSC which can eventually lead to a low-cost high-efficiency III-V-on-Si HBTSC technology.

41 EE - Solar Energy Technologies Office (EE-4S)↗