Engineering topics

Garcia, Ivan

Publications and source records attributed to Garcia, Ivan.

4 records

DOE OSTI2021

Towards a III-V Solar Cell with a Metamorphic Graded Buffer Directly Grown on V-Groove Si Substrates

V-groove Si substrates offer a promising route for the direct growth of III-V solar cells on low-cost, photovoltaic-grade Si. In this work, we develop a method for coalescing GaP nucleated on V-groove substrates into thin films suitable for the growth of III-V solar cells. We demonstrate the ability to suppress nucleation-related defects by modifying the V-groove substrate to cover the (0 0 1)-oriented Si V-groove tops with SiN x . A threading dislocation density (TDD) of 5 × 10 7 cm -2 was measured with electron channeling contrast imaging. Continuing work will focus on further reducing the TDD and the growth of a GaAs solar cell on a GaP on V-groove Si template.

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

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)↗

DOE OSTI2020

High Efficiency 6-Junction Solar Cells for the Global and Direct Spectra

We show 6-junction inverted metamorphic solar cells with high efficiencies under both the global and direct spectrum, and discuss improvements to device components. High voltage AlGaInP subcells are demonstrated on GaAs substrates miscut 2° towards (111)B by using Sb surfactant to reduce atomic ordering. This miscut enables high voltage and low dislocation density GaInAs subcells by using atomically-ordered GaInP-based graded buffers. One-sun efficiencies of 39.2 ± 1.3% under the global spectrum and 39.4 ± 1.1% direct spectrum have been demonstrated by using these high voltage subcell components. For high efficiency under the concentrated direct spectrum, low resistance is also necessary, which requires a challenging and nonintuitive optimization of tunnel junctions and heterobarriers. Increasing the thickness of a (Al)GaInAs spacer layer between the back surface fields (BSF) and tunnel junctions (TJ) of latticemismatched subcells reduces nonlinear resistance, which implies a detrimental interaction between the BSF and TJ. Concentrator devices with optimized spacer layers show reduced effective resistance and maintain fill factor > 75% at 1100 suns. Device efficiencies under the concentrated direct spectrum peak at 47.1 ± 3.2% at 143 suns.

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

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↗