208
S. Ghimire et al.
do not dissociate into free charge-carriers. Thus, the exciton recombination becomes
ultrafast, and the isolated semiconductor nanocrystals or QDs show PL blinking. In
contrast, metal halide perovskite nanocrystals and QDs arranged into superlattices
exhibit long-range carrier migration and delayed radiative recombination. This is
analogous to the long-range diffusion of free charge-carriers in bulk perovskites,
suggesting a weak confinement of photogenerated electron-hole pairs. The formation of new inter-particle energy states in superlattices of PNCs assist in the diffusion
of coulombically uncorrelated electrons and holes. Such freely diffusing electrons
are effectively harvested using C 60 . Therefore, superlattices of PNCs are promising
structures for the development of high-efficiency solar cells.
Acknowledgements S. G. acknowledges the MEXT scholarship for doctoral research, and L.
C. acknowledges the JICA scholarship for doctoral research. V. B. acknowledges financial support
(Grants 15H01099 and 17H05243) from MEXT under the JSPS Grant-in-Aid for Scientific Research
on Innovative Areas “Photosynergetics.”
References
1. Kojima A, Teshima K, Shirai Y, Miyasaka T (2009) Organometal halide perovskites as visiblelight sensitizers for photovoltaic cells. J Am Chem Soc 131:6050–6051
2. Dong Q, Fang NY, Shao Y, Mulligan P, Qiu J, Cao L, Huang J (2015) Electron-hole diffusion
lengths > 175 µm in solution-grown CH 3 NH 3 PbI 3 single crystals. Science 347:967–970
3. deQuilettes DW, Vorpahl SM, Stranks SD, Nagaoka H, Eperon GE, Ziffer ME, Snaith HJ,
Ginger DS (2015) Impact of microstructure on local carrier lifetime in perovskite solar cells.
Science 348:683–686
4. Zhang F, Zhong H, Chen C, Wu X, Hu X, Huang H, Han J, Zou B, Dong Y (2015) Brightly
luminescent and color-tunable colloidal CH 3 NH 3 PbX 3 (X = Br, I, Cl) quantum dots: potential
alternatives for display technology. ACS Nano 9:4533–4542
5. Kim Y-H, Cho H, Heo JH, Kim T-S, Myoung N, Lee C-L, Im SH, Lee T-W (2015) Multicolored
organic/inorganic hybrid perovskite light-emitting diodes. Adv Mater 27:1248–1254
6. Yakunin S, Protesescu L, Krieg F, Bodnarchuk MI, Nedelcu G, Humer M, De Luca G, Fiebig
M, Heiss W, Kovalenko MV (2015) Low-threshold amplified spontaneous emission and lasing
from colloidal nanocrystals of caesium lead halide perovskites. Nat Commun 6:8056
7. Saba M, Cadelano M, Marongiu D, Chen F, Sarritzu V, Sestu N, Figus C, Aresti M, Piras R,
Lehmann AG, Cannas C, Musinu A, Quochi F, Mura A, Bongiovanni G (2014) Correlated
electron-hole plasma in organometal perovskites. Nat Commun 5:5049
8. Yang Y, Yang M, Li Z, Crisp R, Zhu K, Beard MC (2015) Comparison of recombination
dynamics in CH 3 NH 3 PbBr 3 and CH 3 NH 3 PbI 3 perovskite films: influence of exciton binding
energy. J Phys Chem Lett 6:4688–4692
9. Jha A, Duan H-G, Tiwari T, Nayak PK, Snaith HJ, Thorwart M, Miller RJD (2018) Direct observation of ultrafast exciton dissociation in lead iodide perovskite by 2D electronic spectroscopy.
ACS Photonics 5:852–860
10. Phuong LQ, Yamada Y, Nagai M, Maruyama N, Wakamiya A, Kanemitsu Y (2016) Free carriers
versus excitons in CH 3 NH 3 PbI 3 perovskite thin films at low temperatures: charge transfer from
the orthorhombic phase to the tetragonal phase. J Phys Chem Lett 7:2316–2321
11. Blancon J-C, Tsai H, Nie W, Stoumpos CC, Pedesseau L, Katan C, Kepenekian M, Soe CMM,
Appavoo K, Sfeir MY, Tretiak S, Ajayan PM, Kanatzidis MG, Even J, Crochet JJ, Mohite
AD (2017) Extremely efficient internal exciton dissociation through edge states in layered 2D
perovskites. Science 355:1288–1292
S. Ghimire et al.
do not dissociate into free charge-carriers. Thus, the exciton recombination becomes
ultrafast, and the isolated semiconductor nanocrystals or QDs show PL blinking. In
contrast, metal halide perovskite nanocrystals and QDs arranged into superlattices
exhibit long-range carrier migration and delayed radiative recombination. This is
analogous to the long-range diffusion of free charge-carriers in bulk perovskites,
suggesting a weak confinement of photogenerated electron-hole pairs. The formation of new inter-particle energy states in superlattices of PNCs assist in the diffusion
of coulombically uncorrelated electrons and holes. Such freely diffusing electrons
are effectively harvested using C 60 . Therefore, superlattices of PNCs are promising
structures for the development of high-efficiency solar cells.
Acknowledgements S. G. acknowledges the MEXT scholarship for doctoral research, and L.
C. acknowledges the JICA scholarship for doctoral research. V. B. acknowledges financial support
(Grants 15H01099 and 17H05243) from MEXT under the JSPS Grant-in-Aid for Scientific Research
on Innovative Areas “Photosynergetics.”
References
1. Kojima A, Teshima K, Shirai Y, Miyasaka T (2009) Organometal halide perovskites as visiblelight sensitizers for photovoltaic cells. J Am Chem Soc 131:6050–6051
2. Dong Q, Fang NY, Shao Y, Mulligan P, Qiu J, Cao L, Huang J (2015) Electron-hole diffusion
lengths > 175 µm in solution-grown CH 3 NH 3 PbI 3 single crystals. Science 347:967–970
3. deQuilettes DW, Vorpahl SM, Stranks SD, Nagaoka H, Eperon GE, Ziffer ME, Snaith HJ,
Ginger DS (2015) Impact of microstructure on local carrier lifetime in perovskite solar cells.
Science 348:683–686
4. Zhang F, Zhong H, Chen C, Wu X, Hu X, Huang H, Han J, Zou B, Dong Y (2015) Brightly
luminescent and color-tunable colloidal CH 3 NH 3 PbX 3 (X = Br, I, Cl) quantum dots: potential
alternatives for display technology. ACS Nano 9:4533–4542
5. Kim Y-H, Cho H, Heo JH, Kim T-S, Myoung N, Lee C-L, Im SH, Lee T-W (2015) Multicolored
organic/inorganic hybrid perovskite light-emitting diodes. Adv Mater 27:1248–1254
6. Yakunin S, Protesescu L, Krieg F, Bodnarchuk MI, Nedelcu G, Humer M, De Luca G, Fiebig
M, Heiss W, Kovalenko MV (2015) Low-threshold amplified spontaneous emission and lasing
from colloidal nanocrystals of caesium lead halide perovskites. Nat Commun 6:8056
7. Saba M, Cadelano M, Marongiu D, Chen F, Sarritzu V, Sestu N, Figus C, Aresti M, Piras R,
Lehmann AG, Cannas C, Musinu A, Quochi F, Mura A, Bongiovanni G (2014) Correlated
electron-hole plasma in organometal perovskites. Nat Commun 5:5049
8. Yang Y, Yang M, Li Z, Crisp R, Zhu K, Beard MC (2015) Comparison of recombination
dynamics in CH 3 NH 3 PbBr 3 and CH 3 NH 3 PbI 3 perovskite films: influence of exciton binding
energy. J Phys Chem Lett 6:4688–4692
9. Jha A, Duan H-G, Tiwari T, Nayak PK, Snaith HJ, Thorwart M, Miller RJD (2018) Direct observation of ultrafast exciton dissociation in lead iodide perovskite by 2D electronic spectroscopy.
ACS Photonics 5:852–860
10. Phuong LQ, Yamada Y, Nagai M, Maruyama N, Wakamiya A, Kanemitsu Y (2016) Free carriers
versus excitons in CH 3 NH 3 PbI 3 perovskite thin films at low temperatures: charge transfer from
the orthorhombic phase to the tetragonal phase. J Phys Chem Lett 7:2316–2321
11. Blancon J-C, Tsai H, Nie W, Stoumpos CC, Pedesseau L, Katan C, Kepenekian M, Soe CMM,
Appavoo K, Sfeir MY, Tretiak S, Ajayan PM, Kanatzidis MG, Even J, Crochet JJ, Mohite
AD (2017) Extremely efficient internal exciton dissociation through edge states in layered 2D
perovskites. Science 355:1288–1292