Direct Observation of Ultrafast Hole Injection from Lead Halide

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Direct Observation of Ultrafast Hole Injection from Lead Halide Perovskite by Differential Transient Transmission Spectroscopy Kunie Ishioka, Bobby G Barker, Masatoshi Yanagida, Yasuhiro Shirai, and Kenjiro Miyano J. Phys. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.jpclett.7b01663 • Publication Date (Web): 02 Aug 2017 Downloaded from http://pubs.acs.org on August 2, 2017

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The Journal of Physical Chemistry Letters

Direct Observation of Ultrafast Hole Injection from Lead Halide Perovskite by Differential Transient Transmission Spectroscopy Kunie Ishioka,∗,† Bobby G. Barker Jr.,‡ Masatoshi Yanagida,¶ Yasuhiro Shirai,¶ and Kenjiro Miyano¶ Research Center for Advanced Measurement and Characterization, Sengen 1-2-1, National Institute for Materials Science, Tsukuba 305-0047 Japan, Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, SC, USA, and Global Research Center for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Materials Science, Namiki 1-1, Tsukuba 305-0044 Japan E-mail: [email protected]

∗

To whom correspondence should be addressed RCAM-NIMS ‡ Univ. South Carolina ¶ GREEN-NIMS †

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Abstract Efficient charge separation at the interfaces of the perovskite with the carrier transport layers is crucial for perovskite solar cells to achieve high power conversion efficiency. We present systematic experimental study on the hole injection dynamics from MAPbI3 perovskite to three typical hole transport materials (HTMs). We extract the carrier dynamics directly related to the hole injection by employing the pump light with short absorption depth and comparing the transient transmission signals excited on the two sides of the sample. The differential transmission signals reveals the hole injections to PTAA and PEDOT:PSS to be complete within 1 and 2 ps, respectively, and that to NiOx to exhibit an additional slow process of 40 ps time scale. The obtained injection dynamics are discussed in comparison with the device performance of the solar cells containing the same MAPbI3 /HTM interfaces.

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Lead halide perovskite photovoltatic cells have been developing rapidly in the past few years, with their power conversion efficiency (PCE) now exceeding 22%. 1 The perovskites are direct semiconductors, and their photovoltatics can in principle work as a model p-i-n diode. 2 The difficulty in the controlled impurity doping in the perovskites can be circumvented by sandwiching the perovskite film between thin layers of electron- and hole-transporting materials (ETM and HTM) in the planar heterojunction structure. 3 These carrier transporting layers enable efficient and irreversible separation of the electrons and holes photoexcited in the perovskite, and thereby lead to the high PCE of the perovskite solar cells. Whereas various inorganic and organic materials have been explored as ETM and HTM, based on their conduction and valence band energy offsets with respect to those of the perovskite, the actual device performance shows only a weak correlation with the energy levels. 3,4 Time-resolved photoluminescence (PL) and transient absorption (TA) spectroscopies have been employed extensively to investigate the microscopic effects of the ETM and HTM layers on the carrier dynamics in the perovskites. The previous PL studies monitored the injections of the photoexcited carriers into the transport layers indirectly as the suppression of the PL intensity emitted at their recombination and the acceleration in the PL decay time on tens of nanosecond time scale. 5–9 Excitation density-dependences of the PL decay time and of the solar cell external quantum efficiency (EQE) revealed a carrier-injection bottleneck at the interfaces with TiO2 and spiro-OMeTAD at high excitation densities. 10 The extraordinarily long electron and hole diffusion lengths in the perovskites were confirmed by the PL and TA measurements in the visible and THz range on perovskites with and without the ETM and HTM. 11–14 The time scale of the charge injection from the perovskite to the HTM layer itself remains controversial, however, despite the extensive TA studies that aimed to directly time-resolve the injection dynamics. 11,15–23 The time constant of the hole injection from CH3 NH3 PbI3 (MAPbI3 ) to spiroOMeTAD in the previous reports, for example, scattered widely from > +9'?? +@(10000 5701 1337

We also fabricate the solar cells containing the same MAPbI3 /HTM interfaces and mea11 ACS Paragon Plus Environment


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sure their EQE and current density-voltage (J-V) characteristics, 39 whose results are summarized in Fig. 2b and Table 1 as well as in Figs. S1 and S2 in Supporting Information. The solar cells with all the HTMs exhibit good reproducibility in their device performance. 25,26,40 On one hand, the EQE at 400 nm hardly depends on the HTM despite the absorption by PTAA, suggesting the comparable recombination near the MAPbI3 /HTM interfaces under the short-circuit condition. On the other, the values of Voc do not directly correspond to the energy offset in the VBMs but are reduced considerably for the solar cells with PEDOT:PSS and NiOx in comparison with those with PTAA. This is consistent with the most efficient hole injection to PTAA revealed in the present time-resolved study. Moreover, the solar cell with NiOx shows the highest Rs and the lowest Rsh , indicating the poorest transport at the interface and in the perovskite as well as the power loss due to defects. It is likely that NiOx , a hard inorganic semiconductor, induces more disorders and defects in the perovskite film fabricated on top of it due to the chemical reaction between the two materials 38 than the other two soft organic semiconductors, and thus results in the relatively poor device performance. Such defective interface would also lead to the slower hole injection, as we have seen in our transient transmission signals for MAPbI3 /NiOx interface. The correlation between the carrier dynamics and the device performance will be further investigated over wider range of HTMs, ETMs and perovskites by the differential transient transmission technique. The physical mechanism behind the correlation will be examined by monitoring the carrier dynamics of the actual solar cells under working conditions in the transient reflection geometry. In conclusion, we have directly monitored the hole injection dynamics at the interfaces of MAPbI3 with three different HTMs. The differential transient transmission signals have shown that the hole injection is complete within 1 and 2 ps at the MAPbI3 /PTAA and MAPbI3 /PEDOT:PSS interfaces. By contrast, the hole injection at the MAPbI3 /NiOx comprises two steps and takes 40 ps to be complete. The obtained carrier dynamics are consistent with the poor device performances of the solar cell with the HTMs examined. The differ-


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ential transient transmission measurements thus proved to be a powerful tool to investigate the interfacial carrier dynamics using a simple linear optical technique, and the knowledge obtained will contribute to explore novel HTM materials that enable high photovoltatic performance.

Acknowledgement This research was supported by MEXT Program for Development of Environmental Technology using Nanotechnology.

Supporting Information Available The following files are available free of charge. • SI-Ishioka2017JPCL.pdf: on sample preparation, device performance characterization, transient transmission measurements, pump density-dependence of transient transmission, diffusion simulation (PDF). This material is available free of charge via the Internet at http://pubs.acs.org/.

References (1) National Renewable Energy Laboratory. Research Cell Record Efficiency Chart. DOI: www.nrel.gov/pv/assets/images/efficiency-chart.png (accessed 5. 17. 2017). (2) Miyano, K.; Tripathi, N.; Yanagida, M.; Shirai, Y. Lead Halide Perovskite Photovoltaic as a Model p-i-n Diode. Acc. Chem. Res. 2016, 49, 303–310. (3) Kim, H.; Lim, K.-G.; Lee, T.-W. Planar heterojunction organometal halide perovskite solar cells: roles of interfacial layers. Energy Environ. Sci. 2016, 9, 12–30.



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(4) Belisle, R.; Jain, P.; Prasanna, R.; Leijtens, T.; McGehee, M. Minimal Effect of the Hole-Transport Material Ionization Potential on the Open-Circuit Voltage of Perovskite Solar Cells. ACS Energy Lett. 2016, 1, 556–560. (5) Sheng, R.; Ho-Baillie, A.; Huang, S.; Chen, S.; Wen, X.; Hao, X.; Green, M. Methylammonium Lead Bromide Perovskite-Based Solar Cells by Vapor-Assisted Deposition. J. Phys. Chem. C 2015, 119, 3545–3549. (6) Chang, J.; Xiao, J.; Lin, Z.; Zhu, H.; Xu, Q.-H.; Zeng, K.; Hao, Y.; Ouyang, J. Elucidating the charge carrier transport and extraction in planar heterojunction perovskite solar cells by Kelvin probe force microscopy. J. Mater. Chem. A 2016, 4, 17464–17472. (7) Gao, P.; Cho, K.; Abate, A.; Grancini, G.; Reddy, P.; Srivasu, M.; Adachi, M.; Suzuki, A.; Tsuchimoto, K.; Gratzel, M. et al. An efficient perovskite solar cell with symmetrical Zn(ii) phthalocyanine infiltrated buffering porous Al2 O3 as the hybrid interfacial hole-transporting layer. Phys. Chem. Chem. Phys. 2016, 18, 27083–27089. (8) Han, J.; Wang, H.-Y.; Wang, Y.; Yu, M.; Yuan, S.; Sun, P.; Qin, Y.; Guo, Z.-X.; Zhang, J.-P.; Ai, X.-C. Efficient promotion of charge separation and suppression of charge recombination by blending PCBM and its dimer as electron transport layer in inverted perovskite solar cells. RSC Adv. 2016, 6, 112512–112519. (9) Liu, X.; Kong, F.; Tan, Z.; Cheng, T.; Chen, W.; Yu, T.; Guo, F.; Chen, J.; Yao, J.; Dai, S. Diketopyrrolopyrrole or benzodithiophene-arylamine small-molecule hole transporting materials for stable perovskite solar cells. RSC Adv. 2016, 6, 87454–87460. (10) Handa, T.; Tex, D.; Shimazaki, A.; Wakamiya, A.; Kanemitsu, Y. Charge Injection Mechanism at Heterointerfaces in CH3 NH3 PbI3 Perovskite Solar Cells Revealed by Simultaneous Time-Resolved Photoluminescence and Photocurrent Measurements. J. Phys. Chem. Lett. 2017, 8, 954–960.


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(11) Xing, G.; Mathews, N.; Sun, S.; Lim, S.; Lam, Y.; Grätzel, M.; Mhaisalkar, S.; Sum, T. Long-Range Balanced Electron- and Hole-Transport Lengths in OrganicInorganic CH3 NH3 PbI3 . Science 2013, 342, 344–347. (12) Stranks, S.; Eperon, G.; Grancini, G.; Menelaou, C.; Alcocer, M.; Leijtens, T.; Herz, L.; Petrozza, A.; Snaith, H. Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber. Science 2013, 342, 341. (13) Piatkowski, P.; Cohen, B.; Ponseca, C.; Salado, M.; Kazim, S.; Ahmad, S.; Sundstrom, V.; Douhal, A. Unraveling Charge Carriers Generation, Diffusion, and Recombination in Formamidiniurn Lead Triiodide Perovskite Polycrystalline Thin Film. J. Phys. Chem. Lett. 2016, 7, 204–210. (14) Johnston, M.; Herz, L. Hybrid Perovskites for Photovoltaics: Charge-Carrier Recombination, Diffusion, and Radiative Efficiencies. Acc. Chem. Res. 2016, 49, 146–154. (15) Brauer, J.; Lee, Y.; Nazeeruddin, M.; Banerji, N. Ultrafast charge carrier dynamics in CH3 NH3 PbI3 : evidence for hot hole injection into spiro-OMeTAD. J. Mater. Chem. C 2016, 4, 5922–5931. (16) Piatkowski, P.; Cohen, B.; Ramos, F. J.; Nunzio, M. D.; Nazeeruddin, M.; Gratzel, M.; Ahmad, S.; Douhal, A. Direct monitoring of ultrafast electron and hole dynamics in perovskite solar cells. Phys. Chem. Chem. Phys. 2015, 17, 14674–14684. (17) Ponseca, C.; Hutter, E.; Piatkowski, P.; Cohen, B.; Pascher, T.; Douhal, A.; Yartsev, A.; Sundström, V.; Savenije, T. Mechanism of Charge Transfer and Recombination Dynamics in Organo Metal Halide Perovskites and Organic Electrodes, PCBM, and Spiro-OMeTAD: Role of Dark Carriers. J. Am. Chem. Soc. 2015, 137, 16043–16048. (18) Leng, J.; Liu, J.; Zhang, J.; Jin, S. Decoupling Interfacial Charge Transfer from Bulk Diffusion Unravels Its Intrinsic Role for Efficient Charge Extraction in Perovskite Solar Cells. J. Phys. Chem. Lett. 2016, 7, 5056–5061. 15 ACS Paragon Plus Environment


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(19) Corani, A.; Li, M.; Shen, P.; Chen, P.; Guo, T.; Nahhas, A. E.; Zheng, K.; Yartsev, A.; Sundstrom, V.; Ponseca, C. Ultrafast Dynamics of Hole Injection and Recombination in Organometal Halide Perovskite Using Nickel Oxide as p-Type Contact Electrode. J. Phys. Chem. Lett. 2016, 7, 1096–1101. (20) Brauer, J.; Lee, Y.; Nazeeruddin, M.; Banerji, N. Charge Transfer Dynamics from Organometal Halide Perovskite to Polymeric Hole Transport Materials in Hybrid Solar Cells. J. Phys. Chem. Lett. 2015, 6, 3675–3681. (21) Marchioro, A.; Teuscher, J.; Friedrich, D.; Kunst, M.; van de Krol, R.; Moehl, T.; Gratzel, M.; Moser, J.-E. Unravelling the mechanism of photoinduced charge transfer processes in lead iodide perovskite solar cells. Nat Photon 2014, 8, 250–255. (22) Lim, S.; Chong, W.; Solanki, A.; Dewi, H.; Mhaisalkar, S.; Mathews, N.; Sum, T. Modulating carrier dynamics through perovskite film engineering. Phys. Chem. Chem. Phys. 2016, 18, 27119–27123. (23) Peng, B.; Yu, G.; Zhao, Y.; Xu, Q.; Xing, G.; Liu, X.; Fu, D.; Liu, B.; Tan, J.; Tang, W. et al. Achieving Ultrafast Hole Transfer at the Monolayer MoS2 and CH3 NH3 PbI3 Perovskite Interface by Defect Engineering. Acs Nano 2016, 10, 6383–6391. (24) Yanagida, M.; Shimomoto, L.; Shirai, Y.; Miyano, K. Effect of Carrier Transport in NiO on the Photovoltaic Properties of Lead Iodide Perovskite Solar Cells. Electrochem. 2017, 85, in press. (25) Islam, M.; Yanagida, M.; Shirai, Y.; Nabetani, Y.; Miyano, K. NiOx Hole Transport Layer for Perovskite Solar Cells with Improved Stability and Reproducibility. ACS Omega 2017, 2, 2291–2299. (26) Tripathi, N.; Yanagida, M.; Shirai, Y.; Masuda, T.; Han, L.; Miyano, K. Hysteresis-free and highly stable perovskite solar cells produced via a chlorine-mediated interdiffusion method. J. Mater. Chem. A 2015, 3, 12081–12088. 16 ACS Paragon Plus Environment

Page 16 of 24

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(27) Khadka, D.; Shirai, Y.; Yanagida, M.; Masuda, T.; Miyano, K. Enhancement in efficiency and optoelectronic quality of perovskite thin films annealed in MACl vapor. Sustainable Energy Fuels 2017, 1, 755–766. (28) Xie, Z.; Liu, S.; Qin, L.; Pang, S.; Wang, W.; Yan, Y.; Yao, L.; Chen, Z.; Wang, S.; Du, H. et al. Refractive index and extinction coefficient of CH3 NH3 PbI3 studied by spectroscopic ellipsometry. Opt. Mater. Exp. 2015, 5, 29–43. (29) Price, M.; Butkus, J.; Jellicoe, T.; Sadhanala, A.; Briane, A.; Halpert, J.; Broch, K.; Hodgkiss, J.; Friend, R.; Deschler, F. Hot-carrier cooling and photoinduced refractive index changes in organic-inorganic lead halide perovskites. Nat. Commun. 2015, 6, 8420. (30) Anand, B.; Sampat, S.; Danilov, E.; Peng, W.; Rupich, S.; Chabal, Y.; Gartstein, Y.; Malko, A. Broadband transient absorption study of photoexcitations in lead halide perovskites: Towards a multiband picture. Phys. Rev. B 2016, 93, 161205. (31) Manser, J.; Kamat, P. Band filling with free charge carriers in organometal halide perovskites. Nat. Photon. 2014, 8, 737–743. (32) Sum, T.; Mathews, N.; Xing, G.; Lim, S.; Chong, W.; Giovanni, D.; Dewi, H. Spectral Features and Charge Dynamics of Lead Halide Perovskites: Origins and Interpretations. Acc. Chem. Res. 2016, 49, 294–302. (33) Sakamoto, S.; Okumura, M.; Zhao, Z.; Furukawa, Y. Raman spectral changes of PEDOT-PSS in polymer light-emitting diodes upon operation. Chem. Phys. Lett. 2005, 412, 395–398. (34) Endres, J.; Kulbak, M.; Zhao, L.; Rand, B.; Cahen, D.; Hodes, G.; Kahn, A. Electronic structure of the CsPbBr3 /polytriarylamine (PTAA) system. J. Appl. Phys. 2017, 121, 035304.



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(35) Guo, Z.; Manser, J.; Wan, Y.; Kamat, P.; Huang, L. Spatial and temporal imaging of long-range charge transport in perovskite thin films by ultrafast microscopy. Nat. Commun. 2015, 6, 7471. (36) Staub, F.; Hempel, H.; Hebig, J.; Mock, J.; Paetzold, U.; Rau, U.; Unold, T.; Kirchartz, T. Beyond Bulk Lifetimes: Insights into Lead Halide Perovskite Films from Time-Resolved Photoluminescence. Phys. Rev. Appl. 2016, 6, 044017. (37) Dong, Q.; Fang, Y.; Shao, Y.; Mulligan, P.; Qiu, J.; Cao, L.; Huang, J. Electronhole diffusion lengths > 175µm in solution grown CH3 NH3 PbI3 single crystals. Science 2015, 347, 6225. (38) Olthof, S.; Meerholz, K. Substrate-dependent electronic structure and film formation of MAPbI3 perovskites. Sci. Rep. 2017, 7, 40267. (39) Miyano, K.; Yanagida, M.; Tripathi, N.; Shirai, Y. Hysteresis, Stability, and Ion Migration in Lead Halide Perovskite Photovoltaics. J. Phys. Chem. Lett. 2016, 7, 2240–2245. (40) Khadka, D. B.; Shirai, Y.; Yanagida, M.; Ryan, J. W.; Miyano, K. in submission.


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(a) Absorption spectra of the MAPbI3 film without HTM and of the HTM layers only. Broken line and arrow indicate the wavelengths of the pump and probe lights. (b) External quantum efficiencies for the solar cells with three different HTMs. Inset in (b) schematically illustrates the solar cell structure. 206x135mm (144 x 144 DPI)



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Figure 3 Transient transmission changes of MAPbI3 with different HTMs and without, pumped at 400 nm and probed at 720 nm; on picosecond (a), sub-nanosecond (b) and nanosecond (c) time scales. Solid and broken curves denote the transient transmission photoexcited on the HTM and PVK sides, ∆THTM/T and ∆TPVK/T, as illustrated in Fig. 1b. Pump density is 0.5 µJ/cm2. 212x266mm (144 x 144 DPI)


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Figure 4 Differential transient transmission ∆Tdiff= ∆TPVK –∆THTM of MAPbI3 with different HTMs and without. 198x149mm (144 x 144 DPI)



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Figure 5 (a) Calculated hole distributions NPVK and NHTM as a function of distance z from the perovskite/HTM interface for excitation on the PVK and HTM sides at different times t. Diffusion constant D=4 cm2/s and recombination time τ=1.6 ns are used. (b) Calculated differential number of holes NdiffS as a function of time after photoexcitation for different values of D. 227x261mm (144 x 144 DPI)


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Direct Observation of Ultrafast Hole Injection from Lead Halide

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