Printing a solar cell that leaves room for light

A Hebrew University team explored flexible, partly transparent solar cells. Their 2023 study opens a design question: how can a window generate electricity and still function as a window?

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A window has a job before anyone asks it to generate electricity: letting people see out and daylight come in. At the Hebrew University of Jerusalem, Naresh Kumar Pendyala, Shlomo Magdassi and Lioz Etgar explored flexible solar cells with tiny transparent openings. Their 2023 paper describes a laboratory fabrication approach with potential for adding photovoltaic function to existing windows.

The team used inkjet printing to form polymer pillars and a perovskite layer. The transparent regions let some light pass through the device rather than be absorbed. The reported cells reached 9.14% conversion efficiency with 29.3% average transmittance. These are different measurements: one concerns electrical conversion, the other the passage of light. Neither number by itself describes the energy balance of a finished building.

This work belongs within a wider architectural question. In building-integrated photovoltaics, generating materials can become part of roofs, façades or windows rather than sit above them as separate equipment. DOE's explanation notes that tall buildings may have much more wall area than roof area. A façade therefore offers a different surface to investigate, although this research device is not evidence that every wall can economically become a power station.

Window designers must judge more than solar output. A DOE consultation with industry and researchers identified visible-light quality, appearance, insulation, durability and safety among the requirements for photovoltaic glazing. A pleasant room and a productive solar surface are related design goals, but they are not the same measurement. Evaluating both helps prevent a material's attractive laboratory figure from standing in for a complete building design.

The Hebrew University study contributes a way of arranging transparency within a printed device. For a future product, the next questions concern a complete window assembly: how it is connected, protected, installed and maintained over years. Those questions do not diminish the experiment; they identify where development must go. The story moves from a deliberately patterned layer of material towards an everyday object that must satisfy both its occupants and its electrical task.