High‐Performance Near‐Infrared Harvesting Transparent Luminescent Solar Concentrators

Abstract

the architectural envelope as they become more scalable, converting new and existing infrastructure into power-generating sources and dramatically reducing the electrical loss in transmission. [4,5] Transparent luminescent solar concentrators (TLSCs), a key TPV technology, optically shift the solar energy conversion by photoluminescence (PL) that is transported optically (by total internal reflection) to edge-mounted PV cells ( Figure 1A). [1] Due to the absence of electrodes, busbars, and collection grids over the solar harvesting area, the device structure is largely simplified, which enables LSC/TLSC devices to achieve the highest levels of transparency and aesthetics. [4,5] In the past decade, quantum dots, [6][7][8] nanoclusters, [9] and rare-earth ion complexes [10][11][12][13] have been widely investigated as the luminophores in LSC/TLSC systems. Most of these works focus on 1) the improvement of quantum yield (QY), [5,14,15] 2) the modulation of the absorption and emission spectra to minimize the reabsorption loss, [7,8,10,16] and 3) the enhancement of light absorption by matching the absorption spectrum of the luminophores with the peak of the incident solar spectrum. [17][18][19][20] However, the continuous-band absorption characteristics of these luminophores limit their absorption cut-off to ≈435 nm, if a high aesthetic quality and transparency is targeted. Bandgaps beyond 440 nm can result in rapid drops in average visible transmittance (AVT) and color rendering index (CRI). [1,2,21] Utilizing wavelength selective absorbers makes it possible to harvest just the UV or NIR. As selective absorption redshifts beyond 675 nm, the CRI and AVT reach a maximum. [1,2] Therefore, NIR photons between 675 nm and the absorption cut-off of the edge-mounted PV cell can be utilized for power generation, and this range coincides with the peak of the incident AM 1.5G photon flux. Moreover, even with tail absorption in the red-NIR below 675 nm, the resulting blue/green tint is often more visually acceptable than yellow/red tinting, which offers more design freedom for NIR selective-harvesting luminophores. [1,2,22] Optical absorption in organic and molecular semiconductors originates from the transition from the ground state to excited molecular orbitals (e.g., S 0 → S 1 , S 0 → S 2 ). The gap between the excited molecular orbitals (S 1 and S 2 ) results in discontinuity in the density of states, which allows the transmission of photons. The molecular structure can be designed so that this gap is Transparent luminescent solar concentrators (TLSCs) selectively harvest ultraviolet and near-infrared photons. Due to the absence of electrodes, busbars, and collection grids over the solar harvesting area, the device structure enables these devices to achieve the highest levels of transparency and aesthetics. Recently, CO i 8DFIC has been developed as a nonfullerene acceptor in organic photovoltaics with unprecedented performance. In this work, nonfullerene acceptors are introduced into TLSCs as the luminophores. The impact of...

Luminescent Solar Collectors: Quo Vadis?

“…[266] The design of LSCs for solar window application cannot exclusively focus on performances but requires the definition of appropriate balance between efficiency, optical transparency, and social acceptability. [6,7,[270][271][272][273][274] This problem is far from trivial since until now, large-scale LSCs are poorly efficient and a constraint of transparency can impose a further limitation to the efficiency. Wiegman et al investigated the optical properties of an LSC based on 3 µm thin films of europium-doped Lu 2 O 3 in view of possible application in BIPV but the efficiency was strongly limited by scattering losses.…”

“…The system shows a high optical transmittance of 75% and a PCE of 1.24% with J sc ≈ 2 mA cm -2 but C was largely inferior to unity. [274] Recent work has presented original approaches to light-managing systems combining the specific properties of LSCs with switchability that allows to envision some future advanced light-managing BIVP systems combining controlled transmittance and PV generation. [275][276][277] Although BIPV is certainly one of the most promising applications of LSCs, work devoted to the realization of systems with dimensions close to real utilization remains scarce, most of the recent work deals with devices of a few square centimeters while LSCs of 100 cm 2 are generally qualified as "large-area LSCs."…”

Laboratory protocols for measuring and reporting the performance of luminescent solar concentrators

“…In the first camp, the performance of LSCs is mostly evaluated using the same metrics already widely adopted by the PV community, relying on the solar-to-electrical power conversion efficiency as the fundamental figure of merit. [16][17][18][19][20][21][22] This metric certainly becomes important when discussing the commercialisation and deployment of the LSC device into the built environment at the industrial level, as it provides a single, easy-to-understand number that may be used to advertise and sell devices, and gives system designers the means to make calculations as to the impact of the device in their architectures. However, it is much less useful in the research process at the laboratory scale.…”

Vacuum‐Deposited Transparent Organic Photovoltaics for Efficiently Harvesting Selective Ultraviolet and Near‐Infrared Solar Energy

“…[ 13–16 ] The proposed wavelength‐selective TPV developed in this work exhibits a maximum AVT of approximately 77.45%, which is the highest value compared with the previous work in the TPVs, [ 1–3 ] not segmented PVs, [ 56 ] or transparent luminescent solar concentrators. [ 17,18 ] The TPV devices' surface morphology with different electrodes were analyzed by AFM measurements (see Figure S5, Supporting Information). It can be observed that the TPV device with Ag/WO 3 electrode is relatively rough (RMS = 2.63 nm) contributed from the obvious aggregation and granular structure.…”

“…Later on, the research team by Lunt also demonstrated another approach with the NIR harvesting transparent luminescent solar concentrators (LSCs). [ 17,18 ] The transparent LSCs exhibited nontinted transparency >86% in the visible‐light with edge‐mounted Si PV to achieve the PCE > 0.4%. Therefore, TPV with high transparency has great potential in unique solar energy applications, which improves the device performance.…”