Luminescent waveguide-encoded lattices for light harvesting Takashi Lawson 1 , H. Tunstall García 1 , K. Benincasa 2 , K. Saravanamuttu 2 and R.C. Evans 1 1 University of Cambridge, UK, 2 McMaster University, Canada The Internet of Things (IoT) underpins our future smart world where electronic devices are integrated with wireless communication. The rapid growth of the IoT ecosystem is expected to lead to one trillion interconnected devices by 2035. 1 Many of these devices will need to be standalone and portable, creating an urgent demand for off-grid power sources. Commercial crystalline silicon (c-Si) photovoltaic (PV) cells have significant potential for recycling indoor artificial light to perpetually power the wireless electronics that form the basis of the IoT. 2,3 This is primarily due to their cost-effectiveness and abundance. However, c-Si PV cells are optimised to work efficiently under sunlight, whose spectral output is very different to that of artificial light sources. Ambient indoor sources, where the frontrunner is white light-emitting diode lighting, 4 have emission spectra solely in the visible wavelength range. 5 Moreover, c-Si PV cells perform poorly in low-intensity diffuse light - characteristic of indoor lighting - due to significant Shockley-Read-Hall recombination. 6 We demonstrate a new approach to compensate for the limitations of c-Si PV cells for indoor PV based on a new class of photonic material called luminescent waveguide-encoded lattices (LWELs, Figure 1 ). LWELs consist of a thin (ca.1 mm) luminescent polymer film encoded with a patterned array of discrete waveguides. The waveguide array is formed through the self-trapping of incident beams of LED light within a photopolymerisable matrix. 7–9 This leads to local differences in the refractive index where the light rays pass, resulting in the formation of multimode, polychromatic cylindrical waveguide channels permanently inscribed within the polymer matrix. Moreover, the conversion of incident light via photoluminescence is used to match the spectral response of the underlying PV cell to indoor lighting. 10–12 By combining waveguides and luminescence downshifting, the LWEL layer funnels spectrally matched light to the PV surface, resulting in performance improvements of c-Si PV cells under diffuse indoor lighting.
Figure1 | [a] Diagram of an LWEL retrofitted to a PV cell. FOV = field of view. Non-luminescent (left) and luminophore-doped (right) LWEL under [b] white light illumination and [c] UV (365 nm) irradiation. The film size is 50 mm x 50 mm. References 1. P. Sparks,The Route to a Trillion Devices, Cambridge, 2017. 2. I. Mathews et al.,Joule, 2019, 3 , 1415–1426. 3. V. Pecunia et al.,Adv. Energy Mater., 2021, 11 , 2100698. 4. IEA,Lighting, Paris, 2021.
5. B. Li et al.,J. Mater. Chem. C, 2020, 8 , 10676–10695. 6. M. Freunek et al.,IEEE J. Photovoltaics, 2013, 3 , 59–64. 7. I. D. Hosein et al.,Adv. Funct. Mater., 2017, 27 , 1702242. 8. H. Lin et al.,Adv. Opt. Mater., 2019, 7 , 1801091. 9. J. Zhang et al.,J. Am. Chem. Soc., 2006, 128 , 14913–14923. 10. B. McKenna et al.,Adv. Mater., 2017, 29 , 1606491. 11. M. G. Debije et al.,Adv. Energy Mater., 2012, 2 , 12–35. 12. 12 F. Meinardi et al.,Nat. Rev. Mater., 2017, 2 , 17072.
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© The Author(s), 2021
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