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Heterojunction

About: Heterojunction is a(n) research topic. Over the lifetime, 41859 publication(s) have been published within this topic receiving 1000343 citation(s). The topic is also known as: Heterojunction.

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Open accessJournal ArticleDOI: 10.1103/PHYSREVLETT.58.2059
Eli Yablonovitch1Institutions (1)
Abstract: It has been recognized for some time that the spontaneous emission by atoms is not necessarily a fixed and immutable property of the coupling between matter and space, but that it can be controlled by modification of the properties of the radiation field. This is equally true in the solid state, where spontaneous emission plays a fundamental role in limiting the performance of semiconductor lasers, heterojunction bipolar transistors, and solar cells. If a three-dimensionally periodic dielectric structure has an electromagnetic band gap which overlaps the electronic band edge, then spontaneous emission can be rigorously forbidden.

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Topics: Spontaneous emission (63%), Stimulated emission (62%), Heterojunction (54%) ...read more

12,133 Citations


Open accessJournal ArticleDOI: 10.1126/SCIENCE.1243982
18 Oct 2013-Science
Abstract: Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI(3-x)Cl(x)) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of ~100 nanometers. These results justify the high efficiency of planar heterojunction perovskite solar cells and identify a critical parameter to optimize for future perovskite absorber development.

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  • Fig. 2. Photoluminescence measurements and fits to the diffusion model for the mixed halide and triiodide perovskites in the presence of quenchers. (A) Cross-sectional SEM image of a 270-nm thick mixed halide absorber layer with a top hole-quenching layer of Spiro-OMeTAD. (B, C) Time-resolved PL measurements taken at the peak emission wavelength of the (B) mixed halide perovskite and (C) triiodide perovskite with an electron (PCBM; blue triangles) or hole (SpiroOMeTAD; red circles) quencher layer, along with stretched exponential fits to the PMMA data (black squares) and fits to the quenching samples using the diffusion model described in the text (see SM for details). A pulsed (0.3 to 10 MHz) excitation source at 507nm with a fluence of 30nJ/cm 2 impinged on the glass substrate side. Inset in (B): Comparison of the PL decay of the two perovskites (with PMMA) on a longer time scale, with lifetimes τe quoted as the time taken to reach 1/e of the initial intensity.
    Fig. 2. Photoluminescence measurements and fits to the diffusion model for the mixed halide and triiodide perovskites in the presence of quenchers. (A) Cross-sectional SEM image of a 270-nm thick mixed halide absorber layer with a top hole-quenching layer of Spiro-OMeTAD. (B, C) Time-resolved PL measurements taken at the peak emission wavelength of the (B) mixed halide perovskite and (C) triiodide perovskite with an electron (PCBM; blue triangles) or hole (SpiroOMeTAD; red circles) quencher layer, along with stretched exponential fits to the PMMA data (black squares) and fits to the quenching samples using the diffusion model described in the text (see SM for details). A pulsed (0.3 to 10 MHz) excitation source at 507nm with a fluence of 30nJ/cm 2 impinged on the glass substrate side. Inset in (B): Comparison of the PL decay of the two perovskites (with PMMA) on a longer time scale, with lifetimes τe quoted as the time taken to reach 1/e of the initial intensity.
  • Fig. 3. Current-voltage curves for optimized planar heterojunction perovskite solar cells. CH3NH3PbI3-xClx (red line, circle symbols) and CH3NH3PbI3 (black line, square symbols) cells were both measured under 100mWcm -2 AM1.5 simulated sunlight. JSC is the short-circuit current, VOC is the open-circuit voltage, FF is the fill factor, and η is the power conversion efficiency.
    Fig. 3. Current-voltage curves for optimized planar heterojunction perovskite solar cells. CH3NH3PbI3-xClx (red line, circle symbols) and CH3NH3PbI3 (black line, square symbols) cells were both measured under 100mWcm -2 AM1.5 simulated sunlight. JSC is the short-circuit current, VOC is the open-circuit voltage, FF is the fill factor, and η is the power conversion efficiency.
  • Fig. 1: Optical characterization of the mixed halide perovskite CH3NH3PbI3-xClx. (A) Absorption (red squares) and photoluminescence (black circles) spectra of a 270-nm thick layer of CH3NH3PbI3-xClx, coated with PMMA. (B) Transient absorption spectra of CH3NH3PbI3-xClx upon excitation at 500nm (100J/cm 2 pulses). Each gated spectrum has been integrated for 200 ns, and the PL removed. (C) Normalized photobleaching (PB; red squares, left axis) and PL dynamics (black circles, right axis) probed at 750 nm and 770 nm, respectively. Biexponential fitting of the PB data (dark red line) leads to a dominant time constant of τ1=283±6 ns, matching the dynamics of the PL (τe =273±7ns), followed by a long-lived tail. The inset shows the photoinduced absorption (PA) dynamics at 550 nm (blue squares) with a biexponential fit (dark blue line; dominant time constant of τ1=288±12 ns), also matching the dynamics of the PL and the dominant component of the PB.
    Fig. 1: Optical characterization of the mixed halide perovskite CH3NH3PbI3-xClx. (A) Absorption (red squares) and photoluminescence (black circles) spectra of a 270-nm thick layer of CH3NH3PbI3-xClx, coated with PMMA. (B) Transient absorption spectra of CH3NH3PbI3-xClx upon excitation at 500nm (100J/cm 2 pulses). Each gated spectrum has been integrated for 200 ns, and the PL removed. (C) Normalized photobleaching (PB; red squares, left axis) and PL dynamics (black circles, right axis) probed at 750 nm and 770 nm, respectively. Biexponential fitting of the PB data (dark red line) leads to a dominant time constant of τ1=283±6 ns, matching the dynamics of the PL (τe =273±7ns), followed by a long-lived tail. The inset shows the photoinduced absorption (PA) dynamics at 550 nm (blue squares) with a biexponential fit (dark blue line; dominant time constant of τ1=288±12 ns), also matching the dynamics of the PL and the dominant component of the PB.
  • Table 1. Values for diffusion constants (D) and diffusion lengths (LD) from fits to PL decays using the diffusion model described in the text. The errors quoted predominantly arise from perovskite film thickness variations, which are ± 35nm for the triiodide perovskite films and ± 40nm for the mixed halide perovskite films.
    Table 1. Values for diffusion constants (D) and diffusion lengths (LD) from fits to PL decays using the diffusion model described in the text. The errors quoted predominantly arise from perovskite film thickness variations, which are ± 35nm for the triiodide perovskite films and ± 40nm for the mixed halide perovskite films.
Topics: Perovskite solar cell (63%), Perovskite (structure) (60%), Methylammonium lead halide (58%) ...read more

6,875 Citations


Open accessJournal Article
Abstract: Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI(3-x)Cl(x)) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of ~100 nanometers. These results justify the high efficiency of planar heterojunction perovskite solar cells and identify a critical parameter to optimize for future perovskite absorber development.

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Topics: Perovskite (structure) (60%), Trihalide (54%), Triiodide (53%) ...read more

6,454 Citations


Open accessJournal ArticleDOI: 10.1038/SREP00591
Hui-Seon Kim1, Chang-Ryul Lee1, Jeong-Hyeok Im1, Ki Beom Lee1  +8 moreInstitutions (2)
21 Aug 2012-Scientific Reports
Abstract: We report on solid-state mesoscopic heterojunction solar cells employing nanoparticles (NPs) of methyl ammonium lead iodide (CH3NH3)PbI3 as light harvesters. The perovskite NPs were produced by reaction of methylammonium iodide with PbI2 and deposited onto a submicron-thick mesoscopic TiO2 film, whose pores were infiltrated with the hole-conductor spiro-MeOTAD. Illumination with standard AM-1.5 sunlight generated large photocurrents (JSC) exceeding 17 mA/cm2, an open circuit photovoltage (VOC) of 0.888 V and a fill factor (FF) of 0.62 yielding a power conversion efficiency (PCE) of 9.7%, the highest reported to date for such cells. Femto second laser studies combined with photo-induced absorption measurements showed charge separation to proceed via hole injection from the excited (CH3NH3)PbI3 NPs into the spiro-MeOTAD followed by electron transfer to the mesoscopic TiO2 film. The use of a solid hole conductor dramatically improved the device stability compared to (CH3NH3)PbI3 -sensitized liquid junction cells.

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Topics: Perovskite solar cell (60%), Methylammonium halide (57%), Methylammonium lead halide (57%) ...read more

5,830 Citations


Journal ArticleDOI: 10.1063/1.1368156
Abstract: We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

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Topics: Band gap (61%), Heterojunction (57%), Effective mass (solid-state physics) (54%) ...read more

5,816 Citations


Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2022147
20212,664
20202,626
20192,494
20182,407
20172,235

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Topic's top 5 most impactful authors

Nick Holonyak

108 papers, 3.2K citations

Kenji Watanabe

75 papers, 15.5K citations

Fan Ren

73 papers, 1.6K citations

Stephen J. Pearton

72 papers, 1.6K citations

Takashi Taniguchi

68 papers, 12K citations

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