1
|
Xiao C, Jiang CS, Nardone M, Albin D, Danielson A, Munshi AH, Shimpi T, Sampath W, Jones S, Al-Jassim MM, Teeter G, Haegel NM, Moutinho HR. Microscopy Visualization of Carrier Transport in CdSeTe/CdTe Solar Cells. ACS Appl Mater Interfaces 2022; 14:39976-39984. [PMID: 36000715 PMCID: PMC9460435 DOI: 10.1021/acsami.2c09426] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 08/10/2022] [Indexed: 06/15/2023]
Abstract
Solar cells are essentially minority carrier devices, and it is therefore of central importance to understand the pertinent carrier transport processes. Here, we advanced a transport imaging technique to directly visualize the charge motion and collection in the direction of relevant carrier transport and to understand the cell operation and degradation in state-of-the-art cadmium telluride solar cells. We revealed complex carrier transport profiles in the inhomogeneous polycrystalline thin-film solar cell, with the influence of electric junction, interface, recombination, and material composition. The pristine cell showed a unique dual peak in the carrier transport light intensity decay profile, and the dual peak feature disappeared on a degraded cell after light and heat stressing in the lab. The experiments, together with device modeling, suggested that selenium diffusion plays an important role in carrier transport. The work opens a new forum by which to understand the carrier transport and bridge the gap between atomic/nanometer-scale chemical/structural and submicrometer optoelectronic knowledge.
Collapse
Affiliation(s)
- Chuanxiao Xiao
- National
Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Chun-Sheng Jiang
- National
Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Marco Nardone
- Department
of Physics and Astronomy, Bowling Green
State University, Bowling
Green, Ohio 43403, United States
| | - David Albin
- National
Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Adam Danielson
- Colorado
State University, Fort Collins, Colorado 80523, United States
| | - Amit H. Munshi
- Colorado
State University, Fort Collins, Colorado 80523, United States
| | - Tushar Shimpi
- Colorado
State University, Fort Collins, Colorado 80523, United States
| | - Walajabad Sampath
- Colorado
State University, Fort Collins, Colorado 80523, United States
| | - Sean Jones
- National
Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | | | - Glenn Teeter
- National
Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Nancy M. Haegel
- National
Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Helio R. Moutinho
- National
Renewable Energy Laboratory, Golden, Colorado 80401, United States
| |
Collapse
|
2
|
Stetson C, Huey Z, Downard A, Li Z, To B, Zakutayev A, Jiang CS, Al-Jassim MM, Finegan DP, Han SD, DeCaluwe SC. Three-Dimensional Mapping of Resistivity and Microstructure of Composite Electrodes for Lithium-Ion Batteries. Nano Lett 2020; 20:8081-8088. [PMID: 33125240 DOI: 10.1021/acs.nanolett.0c03074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Nanoparticle silicon-graphite composite electrodes are a viable way to advance the cycle life and energy density of lithium-ion batteries. However, characterization of composite electrode architectures is complicated by the heterogeneous mixture of electrode components and nanoscale diameter of particles, which falls beneath the lateral and depth resolution of most laboratory-based instruments. In this work, we report an original laboratory-based scanning probe microscopy approach to investigate composite electrode microstructures with nanometer-scale resolution via contrast in the electronic properties of electrode components. Applying this technique to silicon-based composite anodes demonstrates that graphite, SiOx nanoparticles, carbon black, and LiPAA binder are all readily distinguished by their intrinsic electronic properties, with measured electronic resistivity closely matching their known material properties. Resolution is demonstrated by identification of individual nanoparticles as small as ∼20 nm. This technique presents future utility in multiscale characterization to better understand particle dispersion, localized lithiation, and degradation processes in composite electrodes for lithium-ion batteries.
Collapse
Affiliation(s)
- Caleb Stetson
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
- Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - Zoey Huey
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
- Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - Ali Downard
- Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| | - Zhifei Li
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Bobby To
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Andriy Zakutayev
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Chun-Sheng Jiang
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Mowafak M Al-Jassim
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Donal P Finegan
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Sang-Don Han
- National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Steven C DeCaluwe
- Colorado School of Mines, 1500 Illinois Street, Golden, Colorado 80401, United States
| |
Collapse
|
3
|
Tebyetekerwa M, Cheng Y, Zhang J, Li W, Li H, Neupane GP, Wang B, Truong TN, Xiao C, Al-Jassim MM, Yin Z, Lu Y, Macdonald D, Nguyen HT. Emission Control from Transition Metal Dichalcogenide Monolayers by Aggregation-Induced Molecular Rotors. ACS Nano 2020; 14:7444-7453. [PMID: 32401484 DOI: 10.1021/acsnano.0c03086] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Organic-inorganic (O-I) heterostructures, consisting of atomically thin inorganic semiconductors and organic molecules, present synergistic and enhanced optoelectronic properties with a high tunability. Here, we develop a class of air-stable vertical O-I heterostructures comprising a monolayer of transition-metal dichalcogenides (TMDs), including WS2, WSe2, and MoSe2, on top of tetraphenylethylene (TPE) core-based aggregation-induced emission (AIE) molecular rotors. The created O-I heterostructures yields a photoluminescence (PL) enhancement of up to ∼950%, ∼500%, and ∼330% in the top monolayer WS2, MoSe2, and WSe2 as compared to PL in their pristine monolayers, respectively. The strong PL enhancement is mainly attributed to the efficient photogenerated carrier process in the AIE luminogens (courtesy of their restricted intermolecular motions in the solid state) and the charge-transfer process in the created type I O-I heterostructures. Moreover, we observe an improvement in photovoltaic properties of the TMDs in the heterostructures including the quasi-Fermi level splitting, minority carrier lifetime, and light absorption. This work presents an inspiring example of combining stable, highly luminescent AIE-based molecules, with rich photochemistry and versatile applications, with atomically thin inorganic semiconductors for multifunctional and efficient optoelectronic devices.
Collapse
Affiliation(s)
- Mike Tebyetekerwa
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Yanhua Cheng
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, P.R. China
| | - Jian Zhang
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Weili Li
- School of Material Science and Engineering & National Demonstration Center for Experimental Materials Science and Engineering Education, Jiangsu University of Science and Technology, Zhenjiang 212003, P.R. China
| | - Hongkun Li
- State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, P.R. China
| | - Guru Prakash Neupane
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Bowen Wang
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Thien N Truong
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Chuanxiao Xiao
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | | | - Zongyou Yin
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Yuerui Lu
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Daniel Macdonald
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Hieu T Nguyen
- Research School of Electrical, Energy and Materials Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| |
Collapse
|
4
|
Lancaster M, Mow R, Liu J, Cheek Q, MacInnes MM, Al-Jassim MM, Deutsch TG, Young JL, Maldonado S. Protection of GaInP 2 Photocathodes by Direct Photoelectrodeposition of MoS x Thin Films. ACS Appl Mater Interfaces 2019; 11:25115-25122. [PMID: 31264402 DOI: 10.1021/acsami.9b03742] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Catalytic MoSx thin films have been directly photoelectrodeposited on GaInP2 photocathodes for stable photoelectrochemical hydrogen generation. Specifically, the MoSx deposition conditions were controlled to obtain 8-10 nm films directly on p-GaInP2 substrates without ancillary protective layers. The films were nominally composed of MoS2, with additional MoOxSy and MoO3 species detected and showed no long-range crystalline order. The as-deposited material showed excellent catalytic activity toward the hydrogen evolution reaction relative to bare p-GaInP2. Notably, no appreciable photocurrent reduction was incurred by the addition of the photoelectrodeposited MoSx catalyst to the GaInP2 photocathode under light-limited operating conditions, highlighting the advantageous optical properties of the film. The MoSx catalyst also imparted enhanced durability toward photoelectrochemical hydrogen evolution in acidic conditions, maintaining nearly 85% of the initial photocurrent after 50 h of electrolysis. In total, this work demonstrates a simple method for producing dual-function catalyst/protective layers directly on high-performance, planar III-V photoelectrodes for photoelectrochemical energy conversion.
Collapse
Affiliation(s)
| | - Rachel Mow
- National Renewable Energy Laboratory , 15013 Denver West Pkwy , Golden , Colorado 80401 , United States
| | - Jun Liu
- National Renewable Energy Laboratory , 15013 Denver West Pkwy , Golden , Colorado 80401 , United States
| | | | | | - Mowafak M Al-Jassim
- National Renewable Energy Laboratory , 15013 Denver West Pkwy , Golden , Colorado 80401 , United States
| | - Todd G Deutsch
- National Renewable Energy Laboratory , 15013 Denver West Pkwy , Golden , Colorado 80401 , United States
| | - James L Young
- National Renewable Energy Laboratory , 15013 Denver West Pkwy , Golden , Colorado 80401 , United States
| | | |
Collapse
|
5
|
Ndione PF, Ratcliff EL, Dey SR, Warren EL, Peng H, Holder AM, Lany S, Gorman BP, Al-Jassim MM, Deutsch TG, Zakutayev A, Ginley DS. High-Throughput Experimental Study of Wurtzite Mn 1-x Zn x O Alloys for Water Splitting Applications. ACS Omega 2019; 4:7436-7447. [PMID: 31459840 PMCID: PMC6648451 DOI: 10.1021/acsomega.8b03347] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 04/02/2019] [Indexed: 05/31/2023]
Abstract
We used high-throughput experimental screening methods to unveil the physical and chemical properties of Mn1-x Zn x O wurtzite alloys and identify their appropriate composition for effective water splitting application. The Mn1-x Zn x O thin films were synthesized using combinatorial pulsed laser deposition, permitting for characterization of a wide range of compositions with x varying from 0 to 1. The solubility limit of ZnO in MnO was determined using the disappearing phase method from X-ray diffraction and X-ray fluorescence data and found to increase with decreasing substrate temperature due to kinetic limitations of the thin-film growth at relatively low temperature. Optical measurements indicate the strong reduction of the optical band gap down to 2.1 eV at x = 0.5 associated with the rock salt-to-wurtzite structural transition in Mn1-x Zn x O alloys. Transmission electron microscopy results show evidence of a homogeneous wurtzite alloy system for a broad range of Mn1-x Zn x O compositions above x = 0.4. The wurtzite Mn1-x ZnxO samples with the 0.4 < x < 0.6 range were studied as anodes for photoelectrochemical water splitting, with a maximum current density of 340 μA cm-2 for 673 nm-thick films. These Mn1-x Zn x O films were stable in pH = 10, showing no evidence of photocorrosion or degradation after 24 h under water oxidation conditions. Doping Mn1-x Zn x O materials with Ga dramatically increases the electrical conductivity of Mn1-x Zn x O up to ∼1.9 S/cm for x = 0.48, but these doped samples are not active in water splitting. Mott-Schottky and UPS/XPS measurements show that the presence of dopant atoms reduces the space charge region and increases the number of mid-gap surface states. Overall, this study demonstrates that Mn1-x Zn x O alloys hold promise for photoelectrochemical water splitting, which could be enhanced with further tailoring of their electronic properties.
Collapse
Affiliation(s)
- Paul F. Ndione
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Erin L. Ratcliff
- Department
of Materials Science and Engineering, The
University of Arizona, Tucson, Arizona 85721, United States
| | - Suhash R. Dey
- Department
of Materials Science and Metallurgical Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Hyderabad 502285, India
| | - Emily L. Warren
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Haowei Peng
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Aaron M. Holder
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Stephan Lany
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Brian P. Gorman
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
- Department
of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Mowafak M. Al-Jassim
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Todd G. Deutsch
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - Andriy Zakutayev
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| | - David S. Ginley
- Materials
Science Center, National Renewable Energy
Laboratory, Golden, Colorado 80401, United States
| |
Collapse
|
6
|
Tong J, Song Z, Kim DH, Chen X, Chen C, Palmstrom AF, Ndione PF, Reese MO, Dunfield SP, Reid OG, Liu J, Zhang F, Harvey SP, Li Z, Christensen ST, Teeter G, Zhao D, Al-Jassim MM, van Hest MFAM, Beard MC, Shaheen SE, Berry JJ, Yan Y, Zhu K. Carrier lifetimes of >1 μs in Sn-Pb perovskites enable efficient all-perovskite tandem solar cells. Science 2019; 364:475-479. [DOI: 10.1126/science.aav7911] [Citation(s) in RCA: 537] [Impact Index Per Article: 107.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 02/15/2019] [Accepted: 04/08/2019] [Indexed: 12/20/2022]
Abstract
All-perovskite–based polycrystalline thin-film tandem solar cells have the potential to deliver efficiencies of >30%. However, the performance of all-perovskite–based tandem devices has been limited by the lack of high-efficiency, low–band gap tin-lead (Sn-Pb) mixed-perovskite solar cells (PSCs). We found that the addition of guanidinium thiocyanate (GuaSCN) resulted in marked improvements in the structural and optoelectronic properties of Sn-Pb mixed, low–band gap (~1.25 electron volt) perovskite films. The films have defect densities that are lower by a factor of 10, leading to carrier lifetimes of greater than 1 microsecond and diffusion lengths of 2.5 micrometers. These improved properties enable our demonstration of >20% efficient low–band gap PSCs. When combined with wider–band gap PSCs, we achieve 25% efficient four-terminal and 23.1% efficient two-terminal all-perovskite–based polycrystalline thin-film tandem solar cells.
Collapse
|
7
|
Xiao C, Wang C, Ke W, Gorman BP, Ye J, Jiang CS, Yan Y, Al-Jassim MM. Junction Quality of SnO 2-Based Perovskite Solar Cells Investigated by Nanometer-Scale Electrical Potential Profiling. ACS Appl Mater Interfaces 2017; 9:38373-38380. [PMID: 29027466 DOI: 10.1021/acsami.7b08582] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Electron-selective layers (ESLs) and hole-selective layers (HSLs) are critical in high-efficiency organic-inorganic lead halide perovskite (PS) solar cells for charge-carrier transport, separation, and collection. We developed a procedure to assess the quality of the ESL/PS junction by measuring potential distribution on the cross section of SnO2-based PS solar cells using Kelvin probe force microscopy. Using the potential profiling, we compared three types of cells made of different ESLs but otherwise having an identical device structure: (1) cells with PS deposited directly on bare fluorine-doped SnO2 (FTO)-coated glass; (2) cells with an intrinsic SnO2 thin layer on the top of FTO as an effective ESL; and (3) cells with the SnO2 ESL and adding a self-assembled monolayer (SAM) of fullerene. The results reveal two major potential drops or electric fields at the ESL/PS and PS/HSL interfaces. The electric-field ratio between the ESL/PS and PS/HSL interfaces increased in devices as follows: FTO < SnO2-ESL < SnO2 + SAM; this sequence explains the improvements of the fill factor (FF) and open-circuit voltage (Voc). The improvement of the FF from the FTO to SnO2-ESL cells may result from the reduction in voltage loss at the PS/HSL back interface and the improvement of Voc from the prevention of hole recombination at the ESL/PS front interface. The further improvements with adding an SAM is caused by the defect passivation at the ESL/PS interface, and hence, improvement of the junction quality. These nanoelectrical findings suggest possibilities for improving the device performance by further optimizing the SnO2-based ESL material quality and the ESL/PS interface.
Collapse
Affiliation(s)
- Chuanxiao Xiao
- National Renewable Energy Laboratory , Golden, Colorado 80401, United States
- Colorado School of Mines , Golden, Colorado 80401, United States
| | - Changlei Wang
- The University of Toledo , Toledo, Ohio 43606, United States
| | - Weijun Ke
- The University of Toledo , Toledo, Ohio 43606, United States
| | - Brian P Gorman
- Colorado School of Mines , Golden, Colorado 80401, United States
| | - Jichun Ye
- Ningbo Institute of Industrial Technology, Chinese Academy of Science , Ningbo, Zhejiang Province 315201, China
| | - Chun-Sheng Jiang
- National Renewable Energy Laboratory , Golden, Colorado 80401, United States
| | - Yanfa Yan
- The University of Toledo , Toledo, Ohio 43606, United States
| | - Mowafak M Al-Jassim
- National Renewable Energy Laboratory , Golden, Colorado 80401, United States
| |
Collapse
|
8
|
Abstract
A spin-polarized density-functional theory study is presented here, revealing that a single hole state created by (Ga, N) cluster doping in ZnO contains the contributions from all of the N atoms in the cluster. This is in contrast to the situation where N atoms alone are doped into ZnO, and have a highly localized hole state centered around the dopant N atoms. Hence, this study shows that an enhanced delocalized hole state can be obtained if an appropriate electronic environment is provided.
Collapse
Affiliation(s)
- Muhammad N Huda
- Department of Physics, University of Texas at Arlington, Arlington, TX 76019, USA.
| | | | | |
Collapse
|
9
|
Yin WJ, Wei SH, Al-Jassim MM, Yan Y. Double-hole-mediated coupling of dopants and its impact on band gap engineering in TiO2. Phys Rev Lett 2011; 106:066801. [PMID: 21405484 DOI: 10.1103/physrevlett.106.066801] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Indexed: 05/30/2023]
Abstract
A double-hole-mediated coupling of dopants is unraveled and confirmed in TiO2 by density-functional theory calculations. We find that when a dopant complex on neighboring oxygen sites in TiO2 has net two holes, the holes will strongly couple to each other through significant lattice relaxation. The coupling results in the formation of fully filled impurity bands lying above the valence band of TiO2, leading to a much more effective band gap reduction than that induced by monodoping or conventional donor-acceptor codoping. Our results suggest a new path for semiconductor band gap engineering.
Collapse
Affiliation(s)
- Wan-Jian Yin
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | | | | | | |
Collapse
|
10
|
Yan Y, Jiang CS, Noufi R, Wei SH, Moutinho HR, Al-Jassim MM. Electrically benign behavior of grain boundaries in polycrystalline CuInSe2 films. Phys Rev Lett 2007; 99:235504. [PMID: 18233382 DOI: 10.1103/physrevlett.99.235504] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Indexed: 05/25/2023]
Abstract
The classic grain-boundary (GB) model concludes that GBs in polycrystalline semiconductors create deep levels that are extremely harmful to optoelectronic applications. However, our first-principles density-functional theory calculations reveal that, surprisingly, GBs in CuInSe2 (CIS) do not follow the classic GB model: GBs in CIS do not create deep levels due to the large atomic relaxation in GB regions. Thus, unlike the classic GB model, GBs in CIS are electrically benign, which explains the long-standing puzzling fact that polycrystalline CIS solar cells with remarkable efficiency can be achieved without deliberate GB passivation. This benign electrical character of GBs in CIS is confirmed by our scanning Kelvin probe microscopy measurements on Cu(In,Ga)Se2 chalcopyrite films.
Collapse
Affiliation(s)
- Yanfa Yan
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | | | | | | | | | | |
Collapse
|
11
|
Yan Y, Li J, Wei SH, Al-Jassim MM. Possible approach to overcome the doping asymmetry in wideband gap semiconductors. Phys Rev Lett 2007; 98:135506. [PMID: 17501215 DOI: 10.1103/physrevlett.98.135506] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Indexed: 05/15/2023]
Abstract
The asymmetry doping problem has severely hindered the potential applications of many wideband gap (WBG) materials. Here, we propose a possible approach to overcome this long-standing doping asymmetry problem for WBG semiconductors. Our approach is based on the reduction of the ionization energies of dopants through introduction and effective doping of mutually passivated impurity bands, which can be realized by doping the host with passive donor-acceptor complexes or isovalent impurities. Our density-functional theory calculations demonstrate that this approach provides excellent explanations for the n-type doping of diamond and p-type doping of ZnO, which could not be understood by previous theories. In principle, this approach can be applied to any WBG semiconductors and therefore will open a broad vista for the application of WBG materials.
Collapse
Affiliation(s)
- Yanfa Yan
- National Renewable Energy Laboratory, Golden, CO 80401, USA.
| | | | | | | |
Collapse
|
12
|
Romero MJ, van de Lagemaat J, Mora-Sero I, Rumbles G, Al-Jassim MM. Imaging of resonant quenching of surface plasmons by quantum dots. Nano Lett 2006; 6:2833-7. [PMID: 17163714 DOI: 10.1021/nl061997s] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
In scanning tunneling microscopy (STM), confinement of surface plasmons to the optical cavity formed at the metallic tunneling gap stimulates the emission of light. We demonstrate that quantum dots (QDs) found in such a cavity give rise to discrete, observable transitions in the tunneling luminescence spectrum due to the resonant extinction of the plasmon. The observed resonances represent a fingerprint of the QD and occur at the optical band gap owing to the nearly simultaneous transfer of carriers from both sides of the tunneling gap to the QD. The resonant quenching of surface plasmons enables a new imaging technique, dubbed plasmon resonance imaging, with a spatial resolution potentially similar to that of STM and the energy resolution of optical spectroscopies. This detection and imaging strategy is not restricted to QDs, being of great interest to an entire spectrum of nanostructures, from molecular assemblies and biomolecules to carbon nanotubes.
Collapse
Affiliation(s)
- Manuel J Romero
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401-3393, USA.
| | | | | | | | | |
Collapse
|
13
|
Yan Y, Noufi R, Al-Jassim MM. Grain-boundary physics in polycrystalline CuInSe2 revisited: experiment and theory. Phys Rev Lett 2006; 96:205501. [PMID: 16803181 DOI: 10.1103/physrevlett.96.205501] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Indexed: 05/10/2023]
Abstract
Current studies have attributed the remarkable performance of polycrystalline CuInSe2 (CIS) to anomalous grain-boundary (GB) physics in CIS. The recent theory predicts that GBs in CIS are hole barriers, which prevent GB electrons from recombining. We examine the atomic structure and chemical composition of (112) GBs in Cu(In,Ga)Se2 (CIGS) using high-resolution Z-contrast imaging and nanoprobe x-ray energy-dispersive spectroscopy. We show that the theoretically predicted Cu-vacancy rows are not observed in (112) GBs in CIGS. Our first-principles modeling further reveals that the (112) GBs in CIS do not act as hole barriers. Our results suggest that the superior performance of polycrystalline CIS should not be explained solely by the GB behaviors.
Collapse
Affiliation(s)
- Yanfa Yan
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | | | | |
Collapse
|
14
|
Swartzlander AB, Niles DW, Hasoon FS, Al-Jassim MM. Compositional analysis of CdS/SnO2 films after heat treatments and CdCl2 pretreatments. SURF INTERFACE ANAL 1994. [DOI: 10.1002/sia.740210216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|