Hierarchically Designed Light Trapping Films for All‐Day Operating Semitransparent Photovoltaics

Abstract

Highly efficient light-trapping polymer films are designed to enhance the photocurrent of semitransparent organic photovoltaics (ST-OPVs) in indoor and outdoor conditions. An asymmetric-reflection film fabricated through the novel combination of randomly arranged nanostructures with periodically assembled microstructures exhibits selectivity for the direction of incident light. The film effectively traps light within the device by selectively reflecting light that escapes from the inside out. Moreover, this light-trapping effect is maximized by attaching the films to both sides of the bifacial ST-OPVs operating under solar and indoor sources, simultaneously. Accordingly, the lighttrapping polymer film platform presents short-circuit current density (J SC) enhancement of ST-OPVs by 13.49% and 46.19% under air mass 1.5G and light-emitting diodes (1000 lux) illumination, respectively, and provides new opportunities for ST-OPVs in a variety of practical applications.

Wide Bandgap Polymer with Narrow Photon Harvesting in Visible Light Range Enables Efficient Semitransparent Organic Photovoltaics

“…[18] Meanwhile, highly efficient light-trapping polymer films were designed by Ko et al to enhance the photocurrent of semitransparent OPVs in indoor and outdoor conditions. [19] The films can effectively trap light within the device by selectively reflecting light that escapes from the inside out, leading to the simultaneous improvement on PCE and AVT of semitransparent OPVs. The AVT of semitransparent OPVs can be further improved by decreasing the donor:acceptor (D:A) weight ratio in active layers due to the decreased photon harvesting in the visible light range.…”

Lithography-Free, Large-Area Spatially Segmented Disordered Structure for Light Harvesting in Photovoltaic Modules

“…For all PV systems, optical loss is a major factor that hinders the attainment of the Shockley–Queisser limit: (1) a certain amount of sunlight is reflected off the cell surface, (2) absorbed by the inactive layer of the PV module, or (3) incompletely trapped inside the semiconductor . All these phenomena reduce the photocurrent that can be achieved in cells. − To overcome the limitations, a strategy to reduce the inactive area of the solar cell and efficient light delivery to the active area is highly required, eliminating losses from nonradiative recombination or incomplete absorption. , The incorporation of properly designed nanostructures to control the flow of light reduces the aforementioned optical losses and mitigates optical absorption, increasing the photocurrent, particularly through encapsulation layers. − Encapsulation is the final step in the modularization of solar cells, and it covers the surface of the cell and controls the transmission properties of the incident light to promote maximum conversion in the primary cell without affecting its intrinsic behavior . Based on the design of the photonic structure to deliver sunlight into the active area, structural approaches such as the use of prisms, randomly scattered pyramid structures, , tapered structures, , diffraction gratings, , correlating nanostructure, and periodic/nonperiodic array , have been reported.…”

Semi-transparent organic photovoltaics

“…STOPVs with the reflection films on both sides of the device show reduced light reflection at the bottom substrate and trapped transmitted light inside the device, achieving a higher PCE of 8.36% relative to the bare STOPVs (7.73%). 76 4.3.2 Photonic crystals. Photonic crystals with controlled reflection wavelength can flatten the transmittance spectra of the STOPVs and thus achieve high CRI.…”

“…STOPVs with the reflection films on both sides of the device show reduced light reflection at the bottom substrate and trapped transmitted light inside the device, achieving a higher PCE of 8.36% relative to the bare STOPVs (7.73%). 76…”