Stretchable GaAs Photovoltaics with Designs That Enable High Areal Coverage

Abstract

Recent research in advanced materials and mechanics demonstrates the possibility for integrating inorganic semiconductors with soft, elastomeric substrates to yield systems with linear elastic mechanical responses to strains that signifi cantly exceed those associated with fracture limits of the constituent materials (e.g. ∼ 1% for many inorganics). This outcome can provide stretching to strain levels of tens of percent (in extreme cases, more than 100%), for diverse, reversible modes of deformation, including bending, twisting, stretching or compressing. [1][2][3][4][5][6][7] Interest in these outcomes is motivated by needs in fl exible display, [8][9][10] curvilinear imaging devices, [11][12][13] structural health monitors [ 14 ] and, more recently, in bio-integrated systems [15][16][17] for advanced therapeutic or diagnostic functionality in clinical medicine. In these latter applications, considerations related to toxicity and biocompatibility of the materials are also critically important. Some of the most well developed strategies exploit confi gurations in which brittle, rigid materials accommodate in-plane strains through out-of-plane motions, via buckling or twisting modes. [ 18 ] Such ideas can be exploited in all parts of an integrated system, or only in interconnections between active devices. The latter design can accommodate the largest strains, but its effi cacy decreases as the areal coverage of the devices increases. [ 12 ] As a result, important applications such as those in light capture (i.e., photovolatics) and detection (i.e., photodetectors), where high coverages are often desired, can be diffi cult to address. Here we report designs for stretchable systems that exploit elastomeric substrates with surface relief that confi nes strains at the locations of the interconnections, and away from the devices. The results enable areal coverages and levels of stretchability with relatively low interfacial stress between devices and substrates, compared to similar layouts with conventional, fl at substrates. We describe, using a combination of theory and experiment, the essential mechanics, and then demonstrate the ideas in stretchable solar modules that use ultrathin, single junction GaAs solar cells.A representative layout for a structured substrate designed for this purpose appears in Figure 1 , in which the relief consists of isolated, raised regions (i.e. islands) separated by recessed features (i.e. trenches). The casting and curing processes of soft lithography [ 19 ] provide a convenient means to form such relief, with excellent dimensional control, in elastomers such as poly(dimethylsiloxane) (PDMS). The image of Figure 1a provides a cross sectional view for a representative case where square islands with edge lengths ( l island ) of 800 μ m are separated by trenches with widths ( l trench ) and depths ( h trench ) of 156 μ m and 200 μ m, respectively. The thickness of the underlying PDMS (i.e. base) is 200 μ m. This type of structure is attractive for stretchable systems that incorporate no...

Stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems

“…Strategic features of relief on the elastomer substrates provide a partial solution to this challenge, as demonstrated recently in photovoltaic modules 26,27 . A disadvantage is that levels of stretchability beyond B30% can be difficult to achieve without sacrificing coverage.…”

In‐Plane Deformation Mechanics for Highly Stretchable Electronics

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Stretchable electronics represents a relatively recent class of technology [1,2] of interest partly due to its potential for applications in sensory robotic skins, [3,4] conformal photovoltaic modules, [5,6] wearable communication devices, [7,8] skin-mounted monitors of physiological health, [9][10][11] advanced, soft surgical and clinical diagnostic tools, [11,12] and bioinspired digital cameras. [13,14] A key challenge in each of these systems is in the development of strategies in mechanics that simultaneously allow large levels of elastic stretchability and high areal coverages of active devices built with materials that are themselves not stretchable (e.g., conventional metals) and are, in some cases, highly brittle (e.g., inorganic semiconductors).

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Flexible Photodetectors Based on 1D Inorganic Nanostructures

“…Several kinds of innovative flexible electronic devices have been successfully fabricated, such as flexible solar cells, electronic skins, flexible transistors and circuits, flexible light‐emitting diodes (LEDs), flexible batteries. and flexible photodetectors 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Photodetectors (PDs) are a kind of electronic sensor for sensing light.…”