Autonomous Light Management in Flexible Photoelectrochromic Films Integrating High Performance Silicon Solar Microcells

Abstract

Commercial smart window technologies for dynamic light and heat management in building and automotive environments traditionally rely on electrochromic (EC) materials powered by an external source. This design complicates building-scale installation requirements and substantially increases costs for applications in retrofit construction. Self-powered photoelectrochromic (PEC) windows are an intuitive alternative wherein a photovoltaic (PV) material is used to power the electrochromic device, which modulates the transmission of the incident solar flux. The PV component in this application must be sufficiently transparent and produce enough power to efficiently modulate the EC device transmission. Here, we propose Si solar microcells (μ-cells) that are i) small enough to be visually transparent to the eye, and ii) thin enough to enable flexible PEC devices. Visual transparency is achieved when Si μ-cells are arranged in high pitch (i.e. low-integration density) form factors while maintaining the advantages of a single-crystalline PV material (i.e., long lifetime and high performance).Additionally, the thin dimensions of these Si μ-cells enable fabrication on flexible substrates to realize these flexible PEC devices. The current work demonstrates this concept using WO 3 as the EC material and V 2 O 5 as the ion storage layer, where each component is fabricated via sol-gel methods that afford improved prospects for scalability and tunability in comparison to thermal evaporation methods. The EC devices display fast switching times, as low as 8 seconds, with a modulation in transmission as high as 33%. Integration with two Si μ-cells in series (affording a 1.12 V output) demonstrates an integrated PEC module design with switching times of less than 3 minutes, and a modulation in transmission of 32% with an unprecedented EC:PV areal ratio.

Transparent Zinc‐Mesh Electrodes for Solar‐Charging Electrochromic Windows

“…These features suggest that this window platform is the most promising one among the previously reported electrochromic smart window candidates. [ 34–36 ] The rapid and uniform switching processes of the ZECD window are evident from Figure 3d. Such rapid switching behaviors were further confirmed through chronoamperometry characterization (Figure S5, Supporting Information), where the current density and charge density attained a stable state within 10 s. Further observations, including the optical properties (i.e., reflection, absorption) of the ZECD window using gel electrolyte and the performance of the window using a liquid electrolyte without PVA, are shown in Figures S6 and S7, Supporting Information.…”

Solar power windows: Connecting scientific advances to market signals

“…To date, most commercially deployed active window technologies rely upon switching mechanisms driven by externally supplied power from the building's electric infrastructure 42 . The high labor-related installation costs for replacing traditional IGUs with externally-powered dynamic windows creates a limited market size, in which dynamic windows would only be practical in new building projects 43,44 . However, retrofitting projects far outnumber those of new builds 6 .…”

“…However, retrofitting projects far outnumber those of new builds 6 . Figure Figure 4a shows a 3D rendering of a dynamic, electrochromic double pane IGU coupled with transparent BIPV technology in order to illustrate a self-powered tinting window 36,41,43,44 . Given this design, the PV component absorbs a small portion of light, in both the on and off states, to enable the power production needed for switching.…”

Highly Efficient All-Solid-State WO3-Perovskite Photovoltachromic Cells for Single-Glass Smart Windows

“…To address these constrains, a PECD constituted of Si solar microcells (μ-cells) showing an optical contrast of 32% and a V oc suitable for powering a WO 3 -based EC system was recently proposed. 23 Differently, dye-sensitized solar cell (DSSCs)based PECDs exhibited the highest optical modulation (> 40%) but very low PCE and V oc and slow switching times make them impractical for generating power on a large scale. 24−37 In these last years, PV cells based on either organic semiconductors (OPV) or hybrid halide perovskites reached improved transparency at high efficiency, emerging as new and promising materials for building-integrated applications.…”

“…Apart from these few examples, the EC units of quasi-solid PEC devices reported so far are commonly characterized by gel electrolytes or viscous liquids. [17][18][19]22,23,26,28,33,35,38,41 Herein, we present for the first time, a full solid-state perovskite PVCD fabricated on a single substrate with a simplified configuration in which a semitransparent (ST) perovskite PV cell is combined with a solid-state WO 3 -based EC unit. Such a multifunctional EC system involves the use of a solid-state, dry, and nonsticky polymer electrolyte, allowing for the direct deposition of a highly transparent conductive electrode (TCE) layer atop the electrolyte film.…”