Conversion efficiency limits and bandgap designs for multi-junction solar cells with internal radiative efficiencies below unity

Zhu, Lin; Mochizuki, Takayasu; Yoshita, Masahiro; Chen, Shaoqiang; Kim, Changsu; Akiyama, Hidefumi; Kanemitsu, Yoshihiko

doi:10.1364/oe.24.00a740

Cited by 36 publications

(33 citation statements)

References 24 publications

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“…However, note that η ext is sensitive to not only material quality but also cell geometry, so that, not a pure measure to assess the effects of nonradiative recombination on cell performance. Via the relationship between η ext and internal radiative efficiency ( η int ), the total recombination currents at thermal equilibrium in Equation can be rewritten by

{R_{i}}^{Rad} / {η_{italicext}}^{i} = ((), \frac{1}{{η_{int}}^{i}} - 1) 4 π L_{i} \int_{E_{italicgi}}^{\infty} α_{i} ((), E) B_{i} ((), E) italicdE + {R_{i}}^{Rad} .

…”

Section: Formulations For Detailed Balance Limit and The Cases With Nmentioning

confidence: 99%

“…They incorporate the subcell absorptions from incident sunlight, subcell self-luminescence, and upper-subcell luminescence, which would be used in detailed balance theory 28 and the extended theory with nonradiative recombination losses. 29,30 The proposed absorption models were applied to the rear-textured InGaP/GaAs/InGaAs three-junction solar cells, as examples, to evaluate their absorption spectrum and photo-generated currents (J sc1 , J sc2 , J sc3 ) at various combinations of subcell thicknesses (L 1 , L 2 , L 3 ), and then to pick out the thickness sets satisfying the current matching in stack (J sc1 = J sc2 = J sc3 = J sc ), that is, the thinnest requisite subcell layers. The materials cut-down owing to this light-trapping strategy were also evaluated for various InGaP-subcell (top-cell) thicknesses from 100 to 800 nm, in contrast with that in the traditional flat-rearsurface cells with single-pass and double-pass absorptions.…”

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confidence: 99%

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Modeling and design for low‐cost multijunction solar cell via light‐trapping rear texture technique: Applied in InGaP/GaAs/InGaAs triple junction

Zhu

Hazama

Reddy

et al. 2019

Progress in Photovoltaics

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To realize high efficiency in parallel with low cost, a light‐trapping rear texture was proposed to be implemented in substrate‐free thin‐film multijunction (MJ) cells. A detailed‐balance theory was formulated taking account of the finite light absorption in thin subcells. Such presented absorption model is general and useful to optimize the subcell thickness for MJ solar cells with light‐trapping design. It is applied for InGaP/GaAs/InGaAs triple‐junction solar cells to simulate subcell photocurrents and to obtain the current‐matching (minimum requisite) subcell thicknesses combinations. Furthermore, the detailed‐balance conversion efficiency was estimated for both radiative limit and the cases with below‐unity internal radiative efficiency. For InGaP/GaAs/InGaAs MJ cells with InGaP subcell thickness less than 600 nm, adding a random‐textured rear reflector can enhance light absorption so significantly that over 90% of InGaAs‐cell thickness and even 50% of GaAs‐cell thickness would be cut without any penalty in conversion efficiency, compared with the subcell thicknesses in traditional MJ cells with flat rear reflectors. Additionally, the thickness combination, (InGaP, GaAs, and InGaAs) = (450 nm, 333 nm, and 26 nm), is recommended to achieve both high conversion efficiency and low material cost. This work provides a very important theoretical guidance for the development on low‐cost and high‐efficiency MJ devices.

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{R_{i}}^{Rad} / {η_{italicext}}^{i} = ((), \frac{1}{{η_{int}}^{i}} - 1) 4 π L_{i} \int_{E_{italicgi}}^{\infty} α_{i} ((), E) B_{i} ((), E) italicdE + {R_{i}}^{Rad} .

…”

Section: Formulations For Detailed Balance Limit and The Cases With Nmentioning

confidence: 99%

mentioning

confidence: 99%

Modeling and design for low‐cost multijunction solar cell via light‐trapping rear texture technique: Applied in InGaP/GaAs/InGaAs triple junction

Zhu

Hazama

Reddy

et al. 2019

Progress in Photovoltaics

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“…Each subcell has its own operating point, and its change due to radiation damage has to be understood for further improvement 9 . To understand the electrical behavior of the subcells, our newly introduced all-optical technique would be suited 10 .…”

Section: Introductionmentioning

confidence: 99%

Direct evaluation of influence of electron damage on the subcell performance in triple-junction solar cells using photoluminescence decays

Tex

Nakamura

Imaizumi

et al. 2017

Sci Rep

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Tandem solar cells are suited for space applications due to their high performance, but also have to be designed in such a way to minimize influence of degradation by the high energy particle flux in space. The analysis of the subcell performance is crucial to understand the device physics and achieve optimized designs of tandem solar cells. Here, the radiation-induced damage of inverted grown InGaP/GaAs/InGaAs triple-junction solar cells for various electron fluences are characterized using conventional current-voltage (I–V) measurements and time-resolved photoluminescence (PL). The conversion efficiencies of the entire device before and after damage are measured with I–V curves and compared with the efficiencies predicted from the time-resolved method. Using the time-resolved data the change in the carrier dynamics in the subcells can be discussed. Our optical method allows to predict the absolute electrical conversion efficiency of the device with an accuracy of better than 5%. While both InGaP and GaAs subcells suffered from significant material degradation, the performance loss of the total device can be completely ascribed to the damage in the GaAs subcell. This points out the importance of high internal electric fields at the operating point.

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“…Therefore, highly luminescent semiconductors are excellent light absorber materials for solar cells [3][4][5][6][7][8] and allow for high open-circuit voltages. 2,9 Reversely, excellent solar-cell light absorber materials could be excellent lightemitting materials.…”

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confidence: 99%

Review—Light Emission from Thin Film Solar Cell Materials: An Emerging Infrared and Visible Light Emitter

Kanemitsu

Okano

Phuong

et al. 2017

ECS J. Solid State Sci. Technol.

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In the last decade, there have been extensive studies on fabrication and physics of thin-film solar cell materials and devices. Many high-efficiency solar cell devices have been developed, and the knowledge gained in these studies can be used advantageously to produce bright light-emitting devices. In this review, we summarize recent luminescence spectroscopic studies on new solar-cell materials and discuss their photocarrier dynamics with respect to efficient light emission. © The Author(s) This special issue focuses on fundamental researches and applications for light emitters and phosphors in the infrared and visible spectral region. Here, we would like to introduce novel approaches, applying insights from thin-film solar-cell materials to the development of new light emitting materials. Recent progress in fundamental research on solar cells is remarkable as novel materials such as perovskite thin films, quantum dots, and colloidal nanocrystals being applied to fabrication of solar cells. Huge efforts in this fundamental research area lead to conversion efficiency improvements for many types of solar cells.1 There exist global demands and attention in establishments of affordable, flexible, light-weight and high conversionefficiency devices.The prerequisite as a light absorber for high-efficiency thin-film solar cells, is a direct band-gap semiconductor with large absorption coefficient and band-gap in the near infrared and visible spectral region. 2One of the best indicators of the intrinsic material quality of a semiconductor, which in turn directly determines the carrier loss in a device, is the internal luminescence quantum efficiency. Therefore, highly luminescent semiconductors are excellent light absorber materials for solar cells [3][4][5][6][7][8] and allow for high open-circuit voltages. 2,9 Reversely, excellent solar-cell light absorber materials could be excellent lightemitting materials. In fact, the electroluminescence (EL) measurement is a well-established and widely-used technique for characterizing solar cell devices.10-17 Furthermore, time-resolved photoluminescence (PL) spectroscopy based on modern laser techniques have revealed the charge carrier flow in bulk materials as well as in devices.18-23 PL and EL spectroscopy techniques are not limited to material characterization, but are also able to characterize devices. Taking account of these close relations, utilizing insights and understandings obtained from solar cell research is strategic for developments in novel luminescent materials and devices in the near infrared and visible spectral region.In this short review, we briefly summarize luminescence properties of thin-film solar cell materials that have been recently developed as thin-film light absorbers. By further discussing the photocarrier dynamics, we are able to understand how these materials can be used optimally as light emitters in novel devices. The abundant information from solar cell research can be applied to other devices as well. A deep understanding of the carrier phy...

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Conversion efficiency limits and bandgap designs for multi-junction solar cells with internal radiative efficiencies below unity

Cited by 36 publications

References 24 publications

Modeling and design for low‐cost multijunction solar cell via light‐trapping rear texture technique: Applied in InGaP/GaAs/InGaAs triple junction

Modeling and design for low‐cost multijunction solar cell via light‐trapping rear texture technique: Applied in InGaP/GaAs/InGaAs triple junction

Direct evaluation of influence of electron damage on the subcell performance in triple-junction solar cells using photoluminescence decays

Review—Light Emission from Thin Film Solar Cell Materials: An Emerging Infrared and Visible Light Emitter

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