Renewable energy will power the future of the world. I work on R&D of a promising new solar cell technology based on perovskite semiconductors. My interests - semiconductor device physics, solar cell engineering, inorganic chemistry, and experimental data analysis.
Band Gap Tuning via Lattice Contraction and Octahedral Tilting in Perovskite Materials for Photovoltaics
Journal of the American Chemical Society
2017; 139 (32)
View details for DOI 10.1021/jacs.7b04981
Perovskite-perovskite tandem photovoltaics with optimized band gaps
2016; 354 (6314): 861-865
We demonstrate four- and two-terminal perovskite-perovskite tandem solar cells with ideally matched band gaps. We develop an infrared-absorbing 1.2-electron volt band-gap perovskite, FA0.75Cs0.25Sn0.5Pb0.5I3, that can deliver 14.8% efficiency. By combining this material with a wider-band gap FA0.83Cs0.17Pb(I0.5Br0.5)3 material, we achieve monolithic two-terminal tandem efficiencies of 17.0% with >1.65-volt open-circuit voltage. We also make mechanically stacked four-terminal tandem cells and obtain 20.3% efficiency. Notably, we find that our infrared-absorbing perovskite cells exhibit excellent thermal and atmospheric stability, not previously achieved for Sn-based perovskites. This device architecture and materials set will enable "all-perovskite" thin-film solar cells to reach the highest efficiencies in the long term at the lowest costs.
View details for DOI 10.1126/science.aaf9717
View details for Web of Science ID 000388531900034
View details for PubMedID 27856902
- Atomic layer deposition of vanadium oxide to reduce parasitic absorption and improve stability in n-i-p perovskite solar cells for tandems SUSTAINABLE ENERGY & FUELS 2019; 3 (6): 1517–25
- Solar-driven, highly sustained splitting of seawater into hydrogen and oxygen fuels PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2019; 116 (14): 6624–29
Solar-driven, highly sustained splitting of seawater into hydrogen and oxygen fuels.
Proceedings of the National Academy of Sciences of the United States of America
Electrolysis of water to generate hydrogen fuel is an attractive renewable energy storage technology. However, grid-scale freshwater electrolysis would put a heavy strain on vital water resources. Developing cheap electrocatalysts and electrodes that can sustain seawater splitting without chloride corrosion could address the water scarcity issue. Here we present a multilayer anode consisting of a nickel-iron hydroxide (NiFe) electrocatalyst layer uniformly coated on a nickel sulfide (NiSx) layer formed on porous Ni foam (NiFe/NiSx-Ni), affording superior catalytic activity and corrosion resistance in solar-driven alkaline seawater electrolysis operating at industrially required current densities (0.4 to 1 A/cm2) over 1,000 h. A continuous, highly oxygen evolution reaction-active NiFe electrocatalyst layer drawing anodic currents toward water oxidation and an in situ-generated polyatomic sulfate and carbonate-rich passivating layers formed in the anode are responsible for chloride repelling and superior corrosion resistance of the salty-water-splitting anode.
View details for PubMedID 30886092
- Tin-lead halide perovskites with improved thermal and air stability for efficient all-perovskite tandem solar cells SUSTAINABLE ENERGY & FUELS 2018; 2 (11): 2450–59
- Opportunities and challenges for tandem solar cells using metal halide perovskite semiconductors NATURE ENERGY 2018; 3 (10): 828–38
- Minimizing Current and Voltage Losses to Reach 25% Efficient Monolithic Two-Termina Perovskite-Silicon Tandem Solar Cells ACS ENERGY LETTERS 2018; 3 (9): 2173–80
- Interfacial Effects of Tin Oxide Atomic Layer Deposition in Metal Halide Perovskite Photovoltaics ADVANCED ENERGY MATERIALS 2018; 8 (23)
- Barrier Design to Prevent Metal-Induced Degradation and Improve Thermal Stability in Perovskite Solar Cells ACS ENERGY LETTERS 2018; 3 (7): 1772–78
Terahertz Emission from Hybrid Perovskites Driven by Ultrafast Charge Separation and Strong Electron-Phonon Coupling
2018; 30 (11)
Unusual photophysical properties of organic-inorganic hybrid perovskites have not only enabled exceptional performance in optoelectronic devices, but also led to debates on the nature of charge carriers in these materials. This study makes the first observation of intense terahertz (THz) emission from the hybrid perovskite methylammonium lead iodide (CH3 NH3 PbI3 ) following photoexcitation, enabling an ultrafast probe of charge separation, hot-carrier transport, and carrier-lattice coupling under 1-sun-equivalent illumination conditions. Using this approach, the initial charge separation/transport in the hybrid perovskites is shown to be driven by diffusion and not by surface fields or intrinsic ferroelectricity. Diffusivities of the hot and band-edge carriers along the surface normal direction are calculated by analyzing the emitted THz transients, with direct implications for hot-carrier device applications. Furthermore, photogenerated carriers are found to drive coherent terahertz-frequency lattice distortions, associated with reorganizations of the lead-iodide octahedra as well as coupled vibrations of the organic and inorganic sublattices. This strong and coherent carrier-lattice coupling is resolved on femtosecond timescales and found to be important both for resonant and far-above-gap photoexcitation. This study indicates that ultrafast lattice distortions play a key role in the initial processes associated with charge transport.
View details for PubMedID 29359820
- Compositional Engineering for Efficient Wide Band Gap Perovskites with Improved Stability to Photoinduced Phase Segregation ACS ENERGY LETTERS 2018; 3 (2): 428–35
Optical and Compositional Engineering of Wide Band Gap Perovskites with Improved Stability to Photoinduced Phase Segregation for Efficient Monolithic Perovskite/Silicon Tandem Solar Cells
IEEE. 2018: 0189–91
View details for Web of Science ID 000469200400043
Compositional engineering of tin-lead halide perovskites for efficient and stable low band gap solar cells
IEEE. 2018: 1718–20
View details for Web of Science ID 000469200401161
Mechanism of Tin Oxidation and Stabilization by Lead Substitution in Tin Halide Perovskites
ACS Energy Letters
2017; 2 (9): 2159
View details for DOI 10.1021/acsenergylett.7b00636
Band Gap Tuning via Lattice Contraction and Octahedral Tilting in Perovskite Materials for Photovoltaics.
Journal of the American Chemical Society
2017; 139 (32): 11117–24
Tin and lead iodide perovskite semiconductors of the composition AMX3, where M is a metal and X is a halide, are leading candidates for high efficiency low cost tandem photovoltaics, in part because they have band gaps that can be tuned over a wide range by compositional substitution. We experimentally identify two competing mechanisms through which the A-site cation influences the band gap of 3D metal halide perovskites. Using a smaller A-site cation can distort the perovskite lattice in two distinct ways: by tilting the MX6 octahedra or by simply contracting the lattice isotropically. The former effect tends to raise the band gap, while the latter tends to decrease it. Lead iodide perovskites show an increase in band gap upon partial substitution of the larger formamidinium with the smaller cesium, due to octahedral tilting. Perovskites based on tin, which is slightly smaller than lead, show the opposite trend: they show no octahedral tilting upon Cs-substitution but only a contraction of the lattice, leading to progressive reduction of the band gap. We outline a strategy to systematically tune the band gap and valence and conduction band positions of metal halide perovskites through control of the cation composition. Using this strategy, we demonstrate solar cells that harvest light in the infrared up to 1040 nm, reaching a stabilized power conversion efficiency of 17.8%, showing promise for improvements of the bottom cell of all-perovskite tandem solar cells. The mechanisms of cation-based band gap tuning we describe are broadly applicable to 3D metal halide perovskites and will be useful in further development of perovskite semiconductors for optoelectronic applications.
View details for PubMedID 28704048
- Trade-Off between Trap Filling, Trap Creation, and Charge Recombination Results in Performance Increase at Ultralow Doping Levels in Bulk Heterojunction Solar Cells ADVANCED ENERGY MATERIALS 2016; 6 (24)
- Minimal Effect of the Hole-Transport Material Ionization Potential on the Open-Circuit Voltage of Perovskite Solar Cells ACS ENERGY LETTERS 2016; 1 (3): 556-560
- How the Energetic Landscape in the Mixed Phase of Organic Bulk Heterojunction Solar Cells Evolves with Fullerene Content JOURNAL OF PHYSICAL CHEMISTRY C 2016; 120 (12): 6427-6434