Design Criteria for Micro-Optical Tandem Luminescent Solar Concentrators

Abstract

Traditional concentrating photovoltaic (CPV) systems utilize multijunction cells to minimize thermalization losses, but cannot efficiently capture diffuse sunlight, which contributes to a high levelized cost of energy (LCOE) and limits their use to geographical regions with high direct sunlight insolation. Luminescent solar concentrators (LSCs) harness light generated by luminophores embedded in a light-trapping waveguide to concentrate light onto smaller cells. LSCs can absorb both direct and diffuse sunlight, and thus can operate as flat plate receivers at a fixed tilt and with a conventional module form factor. However, current LSCs experience significant power loss through parasitic luminophore absorption and incomplete light trapping by the optical waveguide. Here we introduce a tandem LSC device architecture that overcomes both of these limitations, consisting of a PLMA polymer layer with embedded CdSe/CdS quantum dot (QD) luminophores and InGaP micro-cells, which serve as a high bandgap absorber on top of a conventional Si photovoltaic. We experimentally synthesize CdSe/CdS QDs with exceptionally high quantum-yield (99%) and ultra-narrowband emission optimally matched to fabricated III-V InGaP microcells. Using a Monte Carlo ray-tracing model, we show the radiative limit power conversion efficiency for a module with these components to be 30.8% diffuse sunlight conditions. These results indicate that a tandem LSC-on-Si architecture could significantly improve upon the efficiency of a conventional Si photovoltaic module with simple and straightforward alterations of the module lamination steps of a Si photovoltaic manufacturing process, with promise for widespread module deployment across diverse geographical regions and energy markets.

Spectrally Matched Quantum Dot Photoluminescence in GaAs-Si Tandem Luminescent Solar Concentrators

“…In addition, this Monte Carlo ray-trace has been verified in the study recently released to investigate efficiencies for a tandem LSC-on-Si architecture with baseline CdSe/CdS QDs coupled to InGaP III-V cells in a coplanar format [1]. !…”

“…We apply a stochastic Monte Carlo ray-trace algorithm in order to closely model designs of luminescent solar concentrator (LSC) with varied luminophore photoluminescence (PL) and absorption profiles [1]. The model takes into account the reflectance, transmittance, and absorbance of the: (i) top PLtrapping filter layer, (ii) the poly(lauryl methacrylate) (PLMA) waveguide layer with uniformly dispersed quantum dot (QD) luminophores at a waveguide area of 8 mm 2 , (iii) the embedded and co-planar GaAs micro-cell at a cell area of .16 mm 2 , (iv) the glass substrate for the GaAs micro-cell, (v) the bottom PLtrapping filter layer, and finally (vi) the PERC Si subcell.…”

“…We include relatively thin, one micrometer thick, airgaps located between the QD-waveguide and the top/bottom PL-trapping filters. Previous work shows increased PL-trapping by use of such structures in order to collect more photon flux in the embedded solar cell via total internal reflection (TIR) [1], [7]. We assume an average index of refraction of n PLMA = 1.44 for the PLMA layer.…”

“…In order to verify that the Monte Carlo and detailed balance models accurately simulate a realistic LSC component with this device architecture and spectral features, we compare the model against experimentally measured data for the Si PERC subcell and the GaAs cell at full illumination [9], [10], [12]. In addition, we compare this LSC ray-trace against separate and independently verified Monte Carlo raytrace models [1], [7], [8].…”

Simulating the Performance of Al0.3Ga0.7As/InP/Ge Multijunction Solar Cells under Variation of Spectral Irradiance and Temperature

“…e combination of the III-V-based solar cells materials such as GaInP, AlGaAs, InP, and GaAs in the form of multijunction solar cells (MJSCs) and their exposure to the several hundreds multiplication of solar radiation had produced the efficiency rate up to 46% at 508 suns for the GaInP/GaAs/GaInAsP/GaInAs system [4]. Some new experimental results and aspects in high-efficient solar cells such as the new design of a vertical epitaxial heterostructure architecture (which allows a high-efficient narrow band cells) [5,6], the use of luminescent solar concentrators (LSCs) [7], or a six-junction solar cell [8] have also expanded our knowledge in solar cells research. Most of the experiments related to the high-efficient MJSC were done using a small specimen prototype, and their realization in the market and industrial scale is still far.…”