J. Eur. Opt. Society-Rapid Publ. 2026, 22, 38 Ó The Author( s), published by EDP Sciences, 2026 https:// doi. org / 10.1051 / jeos / 2026031 Available online at: https:// jeos. edpsciences. org
Journal of the European Optical Society-Rapid Publications
Nano-optoelectronics: from novel materials and nanostructures to innovative applications SHORT COMMUNICATION
Indoor energy harvesting enhancement: Pb-free perovskite solar cell with nanograting contact
Daniel Sarcanean 1, Ángela Barreda 1, Eduardo López-Fraguas 1, Iván Mora-Seró 2, Antonio García-Martín 3, Braulio García-Cámara 1, and Ricardo Vergaz 1, * 1 GDAF-UC3M, Displays and Photonics Applications Group, Universidad Carlos III de Madrid, Spain 2 INAM-UJI, Institute of Advanced Materials, Universitat Jaume I de Castellón, Spain 3 Instituto de Micro y Nanotecnología IMN-CNM, CSIC, CEI UAM + CSIC, Spain
Received 19 December 2025 / Accepted 22 March 2026 Abstract. Halide perovskite materials have spread in solar cells and photodetectors because of their excellent possibilities for tuning their absorption wavelengths, ease of fabrication, and low carbon footprint. However, their main drawbacks are related to their short device lifetime and stability problems in addition to limited efficiency at certain wavelength. For this reason, in this letter, we design a metasurface that can be integrated into a particularly long-life, stable, and sustainable perovskite solar cell with the aim of enhancing its performance under indoor conditions. The metasurface has been designed and numerically simulated to enhance the halide perovskite response at the typical emission wavelengths of indoor LEDs. Adjusting the response of these solar cells to those specific spectral ranges by metasurfaces may create novel energy harvesting devices.
Keywords: Perovskite solar cell, Nanostructured grating, Indoor energy harvesting, Pb-free, FDTD methods.
1 Introduction
Halide perovskite solar cells( PSCs) are revolutionizing solar energy conversion due to their low-cost fabrication, high efficiencies( single-junction reach 26.7 %, and tandem exceed 34 %) [ 1, 2 ], and versatility for diverse applications including IoT and building integration [ 3, 4 ]. Their inherent properties, such as faster carrier dynamics and tunable bandgaps, are key to achieving up to 57 % theoretical efficiency under indoor illumination, significantly exceeding the outdoor Shockley-Queisser limit of 34 % [ 5, 6 ]. However, PSCs struggle with long-term stability due to crystallization defects, moisture, oxygen, and ionic migration [ 7 ]. Research currently focuses on developing stable, durable, and sustainable( Pb-free) materials and architectures to reach full deployment potential [ 8 – 13 ]. One crucial strategy for enhancement is the incorporation of nanophotonic elements like metasurfaces [ 14 ]. These structures effectively manipulate light propagation to boost absorption at relevant wavelengths, increasing photocurrent, and enable functionalities such as color tunability and enhanced light trapping [ 15 – 17 ]. Nanograting structures are particularly promising for improved light management [ 18 ]. They introduce periodic patterns to increase light trapping and extend the optical path, which is crucial for thin-film devices where
* Corresponding author: rvergaz @ ing. uc3m. es light absorption is limited by layer thickness. This approach may either minimize Pb content or increase absorption in defective Sn-based PSCs. Optimized gratings support guided modes and resonances, increasing PCE without adding fabrication complexity [ 19 ]. Since poor positioning or refractive index mismatch can compromise performance [ 20 ], this study focuses on the numerical design of an optimal nanograting metasurface. Our goal is to improve the indoor performance of a Pb-free INAM-UJI PSC [ 21 ] by engineering a 1D diffraction grating within the hole transport layer( HTL) to increase absorbance at characteristic LED illumination peaks.
2 Methodology
Numerical simulations were performed using the finite-difference time-domain( FDTD) method( Lumerical, Ansys Ó). The unit cell reproduces the optically significant structure of the PSC shown in Figure 1a. Based on devices characterized in Ref. [ 21 ], the cell comprises a 200 nm active layer of FASI( FASnI 3) modified with an OM6 organic additive to enhance stability. This layer is sandwiched between carrier extraction layers: a 30 nm hole transport layer( HTL) of PEDOT: PSS and a 30 nm electron transport layer( ETL) of C 60. A 250 nm indium tin oxide( ITO) anode and a 100 nm silver cathode serve as contacts,
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