Journal of Power Sources 476 (2020) 228647 Available online 13 August 2020 0378-7753/© 2020 Elsevier B.V. All rights reserved. Effciency improvement of luminescent solar concentrators using upconversion nitrogen-doped graphene quantum dots Sahar Saeidi , Behzad Rezaei * , Neda Irannejad , Ali Asghar Ensaf Department of Chemistry, Isfahan University of Technology, Isfahan, 84156-83111, IR, Iran HIGHLIGHTS • The upconversion effect of newly synthesized n-GQDs is evaluated. • High quantum effciency of 65% is measured. • Combination of GQDs-LSC-perovskite solar cell is performed for the frst time. • High overlap between IPCE of perovskite solar cell and luminescence of N-GQDs. A R T I C L E INFO Keywords: Luminescent solar concentrator Graphene quantum dots Upconversion luminescent Excitation wavelength-independent Green synthesis ABSTRACT Luminescent solar concentrators (LSCs) incorporated with a large number of luminophores are used as an important trend which increases the effciency of solar cells by concentrating solar energy onto photovoltaics (PVs). However, the main loss in LSC-PV devises results from the incomplete utilization of the solar spectrum. Extending the spectral absorption from UV–Vis into near-infrared (NIR) by means of upconversion particles, reduces the transmission loss of sub-band-gap photons with improved energy alignment. In this study, a new nitrogen-doped graphene quantum dot (N-GQD) possessing upconversion photoluminescence (UCPL), single color emission in UV–Vis–NIR region has been introduced. Large stocks shift of newly synthesized GQDs that is more than 100 nm reduces reabsorption losses signifcantly. Photoluminescence (PL) quantum yield is measured to be 65%. Under solar radiation, the optical features of N-GQDs as absorbers/emitters in polymethyl methac- rylate (PMMA) is studied. Our results demonstrate that GQDs-LSC attached to a perovskite solar cell could enhance effciency. The GQDs-LSCs reaches the power conversion effciency (PCE) more than 4.3 times of PMMA-PV devise. Although the use of N-GQDs hybrid in LSCs for its upconversion feature is at an initial research step, the results prove that it provides a promising way for low cost and nonhazardous solar energy. 1. Introduction Luminescent solar concentrators (LSCs) introduced as devices with two functionalities, the frst one is the absorption of incident photons of sunlight and emission with different wavelengths by luminophores, and the second one is waveguiding of the photons onto a photovoltaic (PV) cell [1,2]. LSCs are planned to decrease the price of generated electricity as a result of concentrating photons and using only a small side area of expensive PVs [3,4]. In these devices, emitted photons are transported over macroscopic distances and converted to electricity by the PVs [5]. In this case, LSCs have become one of the research subjects with wide applications in smart windows, fber optics, active color flters and side accessories of electronic devices [6]. Along with waveguiding, different ways reduce the effciency of LSCs like scattering from the surface, reabsorption by the luminophores or emission into the escape cone defned by Snell’s law [7]. The waveguides were made of glass or plastic as a matrix and luminophores include organic dyes, metal oxides or semiconductor quantum dots (QDs) which were doped into the matrix [3,6]. QDs with the advantages of tunable absorption and emission wavelength, high photoluminescence quantum yield (QY) and photo- stability are considered to be used widely in LSCs [8,9]. GQDs, as a subdivision of luminescent QDs, having low toxicity and cost in com- parison with traditional semiconductor QDs, are more interesting for LSCs [10]. GQDs are zero-dimension allotropes of graphene in which * Corresponding author. E-mail addresses: rezaeimeister@gmail.com, rezaei@iut.ac.ir (B. Rezaei). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour https://doi.org/10.1016/j.jpowsour.2020.228647 Received 30 January 2020; Received in revised form 3 July 2020; Accepted 10 July 2020