Realization of a Photoelectrochemical Cascade for the Generation of Methanol: A Liquid Solar Fuel
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3-terminal tandems↗
Engineering topics
Young, Michelle S.
Publications and source records attributed to Young, Michelle S..
Characterization of multiterminal tandem photovoltaic devices and their subcell coupling
Three-terminal (3T) and four-terminal (4T) tandem photovoltaic (PV) devices using various materials have been increasingly reported in the literature, but measurement standards are lacking. Here, multiterminal devices measured as functions of two load variables are characterized unambiguously as functions of three device voltages or currents on hexagonal plots. We demonstrate these measurement techniques using two GaInP/GaAs tandem solar cells, with a middle contact between the two subcells, as example 3T devices with both series-connected and reverse-connected subcells. Coupling mechanisms between the subcells are quantified within the context of a simple equivalent optoelectronic circuit. Electrical and optical coupling mechanisms are most clearly revealed using coupled dark measurements. These measurements are sensitive enough to observe very small luminescent coupling from the bottom subcell to the top subcell in the prototype 3T device. Quick simplified measurement techniques are also discussed within the context of the complete characterization.
14 SOLAR ENERGY↗
Homogenous Voltage-Matched Strings Using Three-Terminal Tandem Solar Cells: Fundamentals and End Losses
Strings constructed from three-terminal tandem (3TT) solar cells offer the performance benefits of voltage-matching (which reduces sensitivity to spectral variation), but without the subcell voltage isolation required by four-terminal cells. However, the circuitry for a 3TT string can become complex, making circuit analysis more challenging. Here, we illustrate the essential features of “homogenous” voltage-matched (VM) 3TT strings, for which all 3TT cells in the string are nominally identical (with the same design/doping sequence, such that they can be fabricated on the same manufacturing line). Several representative VM string configurations are explicitly considered, and used to describe the general construction of string I(V) curves. End losses intrinsic to these strings are discussed in detail, along with mitigation strategies to minimize their impact. Our analysis agrees with experimental results for eight-cell strings constructed from GaInP/GaAs 3TT devices.
14 SOLAR ENERGY↗
Lamination of transparent conductive adhesives for tandem solar cell applications
A transparent conductive adhesive (TCA) interlayer for mechanically stacked multijunction solar cells provides adhesive strength and electrical connection between sub-cells when stacked. The fabrication of TCA sheets from an ethyl-vinyl acetate (EVA) matrix and silver coated compliant conductive microspheres, similar to industry-standard EVA encapsulant sheets, compatible with a standard lamination process was developed. Blade coating TCA sheets using 3D printed blades and testing of vertical conduction through the interlayer with a TCA conductivity jig allowed for reproducible measurements and low-cost fabrication. The supplemental information provides design files to enable other researchers to produce their own blades and testing jigs. We identified 0.5 mm as an optimal blade height for producing lab-scale TCA sheets and 120 °C at 3 psi for 10 min as the optimal vacuum lamination process to minimize resistance and possible damage to samples. For TCA sheets with coverages between 0.75% and 9%, the series resistance was approximately 0.2 O cm2 which should result in minimal losses for one-sun photovoltaic applications.
14 SOLAR ENERGY↗
Stringing Monolithic Three Terminal III-V Tandems
Tandemdevicesarewellknowntosurpasssinglejunctions.However,thelimitationsofcurrent-matchingisaconcern for changing spectra in terrestrial applications. Three terminal tandem (3T) devices can be more robust to these variations resulting in higher energy yield than single junction devices and two terminal series-connected tandems. We fabricate one-sun 3T tandem devices made of inverted grown III-V tandem (GaInP/t/GaAs) as a prototype of 3T tandems for stringing and measurement demon- strations. We demonstrate 3T tandem measurements that can be used to understand the use of 3T tandems in various constrained configurations. We have demonstrated the improvement of unconstrained 3T tandem cells over 2T series-connected cells as the illumination changes. We present initial results for micro-module with up to 8 3T tandem devices to be strung together.
3T↗