Luminescent solar concentrators (LSCs) can concentrate direct and diffuse solar radiation spatially and energetically to help reduce the overall area of solar cells needed to meet current energy demands. LSCs require luminophores that absorb large fractions of the solar spectrum, emit photons into a light-capture medium with high photoluminescence quantum yields (PLQYs), and do not absorb their own photoluminescence. Luminescent nanocrystals (NCs) with near or above unity PLQYs and Stokes shifts large enough to avoid self-absorption losses are well-suited to meet these needs. In this work, we describe LSCs based on quantum-cutting Yb 3+ :CsPb(Cl 1−x Br x ) 3 NCs that have documented PLQYs as high as ∼200%. Through a combination of solution-phase 1D LSC measurements and modeling, we demonstrate that Yb 3+ :CsPbCl 3 NC LSCs show negligible intrinsic reabsorption losses, and we use these data to model the performance of large-scale 2D LSCs based on these NCs. We further propose a new and unique monolithic bilayer LSC device architecture that contains a Yb 3+ :CsPb(Cl 1−x Br x ) 3 NC top layer above a second narrower-gap LSC bottom layer ( e.g. , based on CuInS 2 NCs), both within the same waveguide and interfaced with the same Si PV for conversion. We extend the modeling to predict the flux gains of such bilayer devices. Because of the exceptionally high PLQYs of Yb 3+ :CsPb(Cl 1−x Br x ) 3 NCs, the optimized bilayer device has a projected flux gain of 63 for dimensions of 70 × 70 × 0.1 cm 3 , representing performance enhancement of at least 19% over the optimized CuInS 2 LSC alone.
more »
« less
Detailed-balance analysis of Yb 3+ :CsPb(Cl 1−x Br x ) 3 quantum-cutting layers for high-efficiency photovoltaics under real-world conditions
Yb 3+ -Doped lead-halide perovskites (Yb 3+ :CsPb(Cl 1−x Br x ) 3 ) have emerged as unique materials combining strong, tunable broadband absorption with near-infrared photoluminescence quantum yields (PLQYs) approaching 200% at ambient temperature. These remarkable properties make Yb 3+ :CsPb(Cl 1−x Br x ) 3 an extremely promising candidate for spectral shaping in high-efficiency photovoltaic devices. Previous theoretical assessments of such “downconversion” devices have predicted single-junction efficiencies up to 40%, but have been highly idealized. Real materials like Yb 3+ :CsPb(Cl 1−x Br x ) 3 have practical limitations such as constrained band-gap and PL energies, non-directional emission, and an excitation-power-dependent PLQY. Hence, it is unclear whether Yb 3+ :CsPb(Cl 1−x Br x ) 3 , or any other non-ideal quantum-cutting material, can indeed boost the efficiencies of real high-performance PV. Here, we examine the thermodynamic, detailed-balance efficiency limit of Yb 3+ :CsPb(Cl 1−x Br x ) 3 on different existing PV under real-world conditions. Among these, we identify silicon heterojunction technology as very promising for achieving significant performance gains when paired with Yb 3+ :CsPb(Cl 1−x Br x ) 3 , and we predict power-conversion efficiencies of up to 32% for this combination. Surprisingly, PL saturation does not negate the improved device performance. Calculations accounting for actual hourly incident solar photon fluxes show that Yb 3+ :CsPb(Cl 1−x Br x ) 3 boosts power-conversion efficiencies at all times of day and year in two representative geographic locations. Predicted annual energy yields are comparable to those of tandem perovskite-on-silicon technologies, but without the need for current matching, tracking, or additional electrodes and inverters. In addition, we show that band-gap optimization in real quantum cutters is inherently a function of their PLQY and the ability to capture that PL. These results provide key design rules needed for development of high-efficiency quantum-cutting photovoltaic devices based on Yb 3+ :CsPb(Cl 1−x Br x ) 3 .
more »
« less
- NSF-PAR ID:
- 10105758
- Date Published:
- Journal Name:
- Energy & Environmental Science
- ISSN:
- 1754-5692
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)Metal halide perovskites have received remarkable attention as photovoltaic (PV) devices. These have already achieved power conversion efficiency higher than 23% rivaling that of silicon-based PV. However, these outstanding efficiencies can only be acquired with lead-based perovskites and the devices are chemically unstable in air and moisture. Therefore, the key to the widespread deployment of perovskite-based solar cell will come down to address their "toxicity" and instability problems. We have taken the challenge to replace lead with other nontoxic or less toxic elements, e.g., Sn, and Ge. We have synthesized Cs(Sn,Ge)X 3 (X=I, Br, and Cl) quantum dots (QDs) using room temperature process. The XRD data showed that the synthesized QDs were yellow hexagonal phase, which was further confirmed by the hexagonal shape of the TEM images of the crystals.more » « less
-
more » « less
In recent years, Cu2ZnSn(S,Se)4(CZTSSe) materials have enabled important progress in associated thin‐film photovoltaic (PV) technology, while avoiding scarce and/or toxic metals; however, cationic disorder and associated band tailing fundamentally limit device performance. Cu2BaSnS4(CBTS) has recently been proposed as a prospective alternative large bandgap (~2 eV), environmentally friendly PV material, with ~2% power conversion efficiency (PCE) already demonstrated in corresponding devices. In this study, a two‐step process (i.e., precursor sputter deposition followed by successive sulfurization/selenization) yields high‐quality nominally pinhole‐free films with large (>1 µm) grains of selenium‐incorporated (
x = 3) Cu2BaSnS4−x Sex (CBTSSe) for high‐efficiency PV devices. By incorporating Se in the sulfide film, absorber layers with 1.55 eV bandgap, ideal for single‐junction PV, have been achieved within the CBTSSe trigonal structural family. The abrupt transition in quantum efficiency data for wavelengths above the absorption edge, coupled with a strong sharp photoluminescence feature, confirms the relative absence of band tailing in CBTSSe compared to CZTSSe. For the first time, by combining bandgap tuning with an air‐annealing step, a CBTSSe‐based PV device with 5.2% PCE (total area 0.425 cm2) is reported, >2.5× better than the previous champion pure sulfide device. These results suggest substantial promise for the emerging Se‐rich Cu2BaSnS4–x Sex family for high‐efficiency and earth‐abundant PV. -
Broadband near infrared (NIR) emission materials are of interest for various applications including non-destructive biomedical imaging. In this work, ytterbium ions (Yb 3+ ) were successfully doped into Cs 2 AgInCl 6 :Cr 3+ (CAIC:Cr 3+ ) double perovskite single crystals (DPSCs) by a facile hydrothermal method. Under 365 nm excitation, the co-doped CAIC:Cr 3+ ,Yb 3+ DPSCs showed broad NIR emission ranging from 800 to 1400 nm, which spanned the NIR-I (700–900 nm) and NIR-II (1000–1700 nm) bio-windows, with an emission band at 1000 nm and a full-width at half maximum (FWHM) of 188 nm. It is found that Yb 3+ ion doping could effectively improve the photoluminescence (PL) performance of CAIC:Cr 3+ DPSCs. Compared to the photoluminescence quantum yield (PLQY) of 22.5% for the single doped CAIC:Cr 3+ , the co-doped CAIC:Cr 3+ ,Yb 3+ DPSCs show a higher PLQY of ∼45%, which is attributed to the synergistic effect of reduced non-radiative recombination due to defect passivation and increase in crystallinity, and energy transfer (ET) of self-trapped excitons (STEs) to Cr 3+ . As a demonstration of applications, NIR pc-LEDs were fabricated by combining the as-synthesized NIR-emitting phosphor CAIC:Cr 3+ ,Yb 3+ with InGaN UV chips ( λ em = 365 nm) and used to image veins in a palm and for night vision using a NIR camera. The results suggest that the synthesized CAIC:Cr 3+ ,Yb 3+ DPSCs have great potential in biological applications.more » « less
-
more » « less
Abstract Recently, the stability of organic–inorganic perovskite thin films under thermal, photo, and moisture stresses has become a major concern for further commercialization due to the high volatility of the organic cations in the prototype perovskite composition (CH3NH3PbI3). All inorganic cesium (Cs) based perovskite is an alternative to avoid the release or decomposition of organic cations. Moreover, substituting Pb with Sn in the organic–inorganic lead halide perovskites has been demonstrated to narrow the bandgap to 1.2–1.4 eV for high‐performance perovskite solar cells. In this work, a series of CsPb1−
x Snx IBr2perovskite alloys via one‐step antisolvent method is demonstrated. These perovskite films present tunable bandgaps from 2.04 to 1.64 eV. Consequently, the CsPb0.75Sn0.25IBr2with homogeneous and densely crystallized morphology shows a remarkable power conversion efficiency of 11.53% and a highV ocof 1.21 V with a much improved phase stability and illumination stability. This work provides a possibility for designing and synthesizing novel inorganic halide perovskites as the next generation of photovoltaic materials.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9ee01493d
