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Hybrid Perovskites for Multijunction Tandem Solar Cells and Solar Fuels. A Virtual Issue
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al. identifies key parameters to achieve power conversion efficiency limits for all-perovskite tandem (33.8%), all-perovskite triple (36.6%), and perovskite tandem in silicon cells (38.8%).3 Efforts to develop tandem solar cells with perovskite−bulk heterojunction photovoltaic architecture have also shown initial success to achieve efficiency as high as 13%.20,21
etal halide perovskite solar cells, which have reached efficiency greater than 22%, have drawn the attention of energy researchers worldwide. Efforts are underway to commercialize perovskite photovoltaics and make them a competitive technology.1,2 Although a singlejunction perovskite solar cell is not likely to exceed the efficiency of a single-junction silicon solar cell (∼26%), it offers new opportunities to maximize the photoconversion efficiency.3 One such procedure is to segregate the absorption of incident light based on the semiconductors that are placed in tandem with a gradient bandgap, a technique that is commonly referred to as multijunction photovoltaics.3,4 As shown with III−V based solar cells (e.g., GaAs, GaP), it is possible to boost the efficiency of solar cells to greater than 38% with double-junction and triple-junction devices.5 However, the deposition methods (e.g., molecular organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE)) used to make III−V tandem devices are too cumbersome and expensive for large-scale production of photovoltaics (PV). The solution processability of metal halide perovskites and the ability to tune their bandgap (1.2−2.3 eV) through compositional changes of ABX3 perovskite structure make them attractive candidates for developing multijunction solar cells.6 Although compositional control allows fine-tuning of the bandgap of mixed halide perovskites, the phase segregation events under irradiation can hamper the goal of achieving improved efficiency.7,8 The designing of multijunction solar cells is rather complex (see Figure 1). Each monolithic semiconductor layer should be carefully laid down with minimal disturbance of the interlayers and should maximize the absorption of incident photons by minimizing parasitic absorption and interference effects. At the same time, these tandem semiconductor layers should collectively exhibit photovoltaic diode characteristics.3 This virtual issue highlights papers recently published in three Letters journals of ACS Publications (ACS Energy Letters, The Journal of Physical Chemistry Letters, and Nano Letters) that focus on the development of multijunction tandem perovskite solar cells and tandem design to drive photocatalytic generation of solar fuels. Early efforts include integration of PV performance of different semiconductors through two- and four-terminal tandem solar cells.9−12 One early effort has been the integration of lead halide perovskite films with Si13−17 and CIGS18,19 photovoltaic architecture to improve the light capture and enhance the photoconversion efficiency. The initial success of achieving efficiency greater than 20% with these tandem solar cells is paving the way to exceed the efficiency of single-junction Si solar cells. While research of perovskite tandem solar cells is in its infancy, new strategies to design cooperative interfaces can lead to the development of double- and triple-junction solar cells. The recent analysis of the material stacks by Hörantner et © 2017 American Chemical Society
Figure 1. Design strategies for double-junction and triple-junction solar cells. Reprinted from ref 3. Copyright American Chemical Society 2017.
Another aspect of perovskite tandem findings is in the area of solar fuels.22 The visible responsive catalysts, such as BiVO4 and Fe2O3, require external bias to carry out water splitting or CO2 reduction into fuels. Perovskite solar cells with their high opencircuit voltage and extended response in the visible and near-
Figure 2. Schematic diagram of the tandem BiVO4−CH3NH3PbI3 device for solar fuels generation. The perovskite solar cell harnesses transmitted photons above 500 nm, and the resulting photogenerated electrons drive H2 production. Reprinted from ref 23. Copyright American Chemical Society 2015. Received: November 16, 2017 Accepted: November 16, 2017 Published: November 22, 2017 28
DOI: 10.1021/acsenergylett.7b01134 ACS Energy Lett. 2018, 3, 28−29
Energy Focus
http://pubs.acs.org/journal/aelccp
Energy Focus
ACS Energy Letters
Heben, M. J. Probing Photocurrent Nonuniformities in the Subcells of Monolithic Perovskite/Silicon Tandem Solar Cells. J. Phys. Chem. Lett. 2016, 7, 5114−5120. (12) Adhyaksa, G. W. P.; Johlin, E.; Garnett, E. C. Nanoscale Back Contact Perovskite Solar Cell Design for Improved Tandem Efficiency. Nano Lett. 2017, 17, 5206−5212. (13) Werner, J.; Weng, C. H.; Walter, A.; Fesquet, L.; Seif, J. P.; De Wolf, S.; Niesen, B.; Ballif, C. Efficient Monolithic Perovskite/Silicon Tandem Solar Cell with Cell Area > 1 cm2. J. Phys. Chem. Lett. 2016, 7, 161−166. (14) Futscher, M. H.; Ehrler, B. Modeling the Performance Limitations and Prospects of Perovskite/Si Tandem Solar Cells under Realistic Operating Conditions. ACS Energy Lett. 2017, 2, 2089−2095. (15) Werner, J.; Barraud, L.; Walter, A.; Bräuninger, M.; Sahli, F.; Sacchetto, D.; Tétreault, N.; Paviet-Salomon, B.; Moon, S.-J.; Allebé, C.; et al. Efficient Near-Infrared-Transparent Perovskite Solar Cells Enabling Direct Comparison of 4-Terminal and Monolithic Perovskite/Silicon Tandem Cells. ACS Energy Lett. 2016, 1, 474−480. (16) Lang, F.; Gluba, M. A.; Albrecht, S.; Rappich, J.; Korte, L.; Rech, B.; Nickel, N. H. Perovskite Solar Cells with Large-Area CVDGraphene for Tandem Solar Cells. J. Phys. Chem. Lett. 2015, 6, 2745− 2750. (17) Futscher, M. H.; Ehrler, B. Efficiency Limit of Perovskite/Si Tandem Solar Cells. ACS Energy Lett. 2016, 1, 863−868. (18) Guchhait, A.; Dewi, H. A.; Leow, S. W.; Wang, H.; Han, G. F.; Suhaimi, F. B.; Mhaisalkar, S.; Wong, L. H.; Mathews, N. Over 20% Efficient CIGS-Perovskite Tandem Solar Cells. ACS Energy Lett. 2017, 2, 807−812. (19) Kranz, L.; Abate, A.; Feurer, T.; Fu, F.; Avancini, E.; Löckinger, J.; Reinhard, P.; Zakeeruddin, S. M.; Grätzel, M.; Buecheler, S.; Tiwari, A. N. High-Efficiency Polycrystalline Thin Film Tandem Solar Cells. J. Phys. Chem. Lett. 2015, 6, 2676−2681. (20) Liu, Y.; Hong, Z.; Chen, Q.; Chang, W.; Zhou, H.; Song, T.-B.; Young, E.; Yang, Y.; You, J.; Li, G.; Yang, Y. Integrated Perovskite/ Bulk-Heterojunction toward Efficient Solar Cells. Nano Lett. 2015, 15, 662−668. (21) Dong, S.; Liu, Y. S.; Hong, Z.; Yao, E.; Sun, P.; Meng, L.; Lin, Y.; Huang, J.; Li, G.; Yang, Y. Unraveling the High Open Circuit Voltage and High Performance of Integrated Perovskite/Organic BulkHeterojunction Solar Cells. Nano Lett. 2017, 17, 5140−5147. (22) Rothschild, A.; Dotan, H. Beating the Efficiency of Photovoltaics-Powered Electrolysis with Tandem Cell Photoelectrolysis. ACS Energy Lett. 2017, 2, 45−51. (23) Chen, Y.-S.; Manser, J. S.; Kamat, P. V. All Solution-Processed Lead Halide Perovskite-BiVO4 Tandem Assembly for Photolytic Solar Fuels Production. J. Am. Chem. Soc. 2015, 137, 974−981. (24) Zhou, X. H.; Liu, R.; Sun, K.; Chen, Y. K.; Verlage, E.; Francis, S. A.; Lewis, N. S.; Xiang, C. X. Solar-Driven Reduction of 1 atm of CO2 to Formate at 10% Energy-Conversion Efficiency by Use of a TiO2-Protected III-V Tandem Photoanode in Conjunction with a Bipolar Membrane and a Pd/C Cathode. ACS Energy Lett. 2016, 1, 764−770. (25) Gurudayal, D.; Sabba; Kumar, M. H.; Wong, L. H.; Barber, J.; Grätzel, M.; Mathews, N. Perovskite−Hematite Tandem Cells for Efficient Overall Solar Driven Water Splitting. Nano Lett. 2015, 15, 3833−3839.
infrared make them suitable to couple with a photoelectrolysis cell in a tandem fashion (see, for example, Figure 2). The success shown in achieving H2 production23−25 and conversion of CO2 to formate25 through a few initial studies demonstrates the ability to achieve efficiencies greater than 10%. The low bandgap and large absorption coefficient of lead iodide hybrid perovskites make them good candidates for developing tandem solar cells. By carefully designing tandem architecture it should be possible to achieve photoconversion efficiency greater than that of single-junction solar cells. Indeed, achieving efficiencies greater than 30% should be the next goal for metal halide perovskite-based multijunction tandem solar cells.
Prashant V. Kamat, Editor-in-Chief, ACS Energy Letters
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University of Notre Dame
AUTHOR INFORMATION
ORCID
Prashant V. Kamat: 0000-0002-2465-6819 Notes
Views expressed in this Energy Focus are those of the author and not necessarily the views of the ACS. The author declares no competing financial interest.
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PAPERS IN THE METAL-HALIDE PEROVSKITE NANOCRYSTALS VIRTUAL ISSUE
(1) Berry, J. J.; van de Lagemaat, J.; Al-Jassim, M. M.; Kurtz, S.; Yan, Y.; Zhu, K. Perovskite Photovoltaics: The Path to a Printable Terawatt-Scale Technology. ACS Energy Lett. 2017, 2, 2540−2544. (2) Ono, L. K.; Park, N.-G.; Zhu, K.; Huang, W.; Qi, Y. Perovskite Solar CellsTowards Commercialization. ACS Energy Lett. 2017, 2, 1749−1751. (3) Hörantner, M. T.; Leijtens, T.; Ziffer, M. E.; Eperon, G. E.; Christoforo, M. G.; McGehee, M. D.; Snaith, H. J. The Potential of Multijunction Perovskite Solar Cells. ACS Energy Lett. 2017, 2, 2506− 2513. (4) Sheng, R.; Ho-Baillie, A. W. Y.; Huang, S.; Keevers, M.; Hao, X.; Jiang, L.; Cheng, Y.-B.; Green, M. A. Four-Terminal Tandem Solar Cells Using CH3NH3PbBr3 by Spectrum Splitting. J. Phys. Chem. Lett. 2015, 6, 3931−3934. (5) Vaisman, M.; Fan, S.; Nay Yaung, K.; Perl, E.; Martín-Martín, D.; Yu, Z. J.; Leilaeioun, M.; Holman, Z. C.; Lee, M. L. 15.3%-Efficient GaAsP Solar Cells on GaP/Si Templates. ACS Energy Lett. 2017, 2, 1911−1918. (6) Huang, H.; Bodnarchuk, M. I.; Kershaw, S. V.; Kovalenko, M. V.; Rogach, A. L. Lead Halide Perovskite Nanocrystals in the Research Spotlight: Stability and Defect Tolerance. ACS Energy Lett. 2017, 2, 2071−2083. (7) Braly, I. L.; Stoddard, R. J.; Rajagopal, A.; Uhl, A. R.; Katahara, J. K.; Jen, A. K. Y.; Hillhouse, H. W. Current-Induced Phase Segregation in Mixed Halide Hybrid Perovskites and its Impact on Two-Terminal Tandem Solar Cell Design. ACS Energy Lett. 2017, 2, 1841−1847. (8) Samu, G. F.; Janáky, C.; Kamat, P. V. A Victim of Halide Ion Segregation. How Light Soaking Affects Solar Cell Performance of Mixed Halide Lead Perovskites. ACS Energy Lett. 2017, 2, 1860−1861. (9) Lee, J. W.; Hsieh, Y. T.; De Marco, N.; Bae, S. H.; Han, Q. F.; Yang, Y. Halide Perovskites for Tandem Solar Cells. J. Phys. Chem. Lett. 2017, 8, 1999−2011. (10) Beal, R. E.; Slotcavage, D. J.; Leijtens, T.; Bowring, A. R.; Belisle, R. A.; Nguyen, W. H.; Burkhard, G. F.; Hoke, E. T.; McGehee, M. D. Cesium Lead Halide Perovskites with Improved Stability for Tandem Solar Cells. J. Phys. Chem. Lett. 2016, 7, 746−751. (11) Song, Z. N.; Werner, J.; Shrestha, N.; Sahli, F.; De Wolf, S.; Niesen, B.; Watthage, S. C.; Phillips, A. B.; Ballif, C.; Ellingson, R. J.; 29
DOI: 10.1021/acsenergylett.7b01134 ACS Energy Lett. 2018, 3, 28−29
