for this interface architecture. Another underestimated degradation mechanism we propose is
the reaction between the I2 from perovskite and
the HTMs with HOMO levels of around –5.0 eV
near the oxidation potential of I–/I3–. After a
2-min exposure to I2 vapor, both P3HT and spiro-MeOTAD films exhibited notable color changes,
which we mainly attributed to their polaron absorption after reaction with I2. In strong contrast,
PDCBT maintained its purple color unchanged
(Fig. 4I), which demonstrates its robustness under
I2 vapor treatment due to a lower HOMO level
approaching –5.3 eV. All of these findings highlight the importance of the deep HOMO level of
H TMs (Fig. 4J) in efficient and stable perovskite
solar cells and lead us to properly design hetero-junction interfaces for perovskite solar cells with
enhanced efficiency and longevity.
REFERENCES AND NOTES
1. National Center for Photovoltaics (NCPV) at the National
Renewable Energy Laboratory (NREL), “Best research-cell
2. H. J. Snaith et al., J. Phys. Chem. Lett. 5, 1511–1515
3. T. M. Brenner, D. A. Egger, L. Kronik, G. Hodes, D. Cahen,
Nat. Rev. Mater. 1, 15007 (2016).
4. B. Hailegnaw, S. Kirmayer, E. Edri, G. Hodes, D. Cahen, J. Phys.
Chem. Lett. 6, 1543–1547 (2015).
5. C. Eames et al., Nat. Commun. 6, 7497 (2015).
6. F. Bella et al., Science 354, 203–206 (2016).
7. X. Li et al., Science 353, 58–62 (2016).
8. M. Saliba et al., Science 354, 206–209 (2016).
9. E. T. Hoke et al., Chem. Sci. 6, 613–617 (2015).
10. M. Saliba et al., Nat. Energy 1, 15017 (2016).
11. M. A. Green, A. Ho-Baillie, H. J. Snaith, Nat. Photonics 8,
12. C. C. Chueh, C. Z. Li, A. K. Y. Jen, Energy Environ. Sci. 8,
13. P. Ganesan et al., Energy Environ. Sci. 8, 1986–1991
14. G. W. Kim et al., Energy Environ. Sci. 9, 2326–2333 (2016).
15. Y. Liu et al., Adv. Mater. 28, 440–446 (2016).
16. P. Schulz et al., ACS Appl. Mater. Interfaces 8, 31491–31499
17. P. Liu et al., Appl. Phys. Lett. 106, 193903 (2015).
18. J. Xu et al., Adv. Mater. 28, 2807–2815 (2016).
19. Y. Hou et al., Adv. Energy Mater. 5, 1500543 (2015).
20. See supplementary materials.
21. Y. Hou et al., Adv. Mater. Interfaces 4, 1700007 (2017).
22. Y. Hou et al., Adv. Mater. 28, 5112–5120 (2016).
23. M. Zhang, X. Guo, W. Ma, H. Ade, J. Hou, Adv. Mater. 26,
24. X. Lan, S. Masala, E. H. Sargent, Nat. Mater. 13, 233–240
25. J. Gao et al., Nano Lett. 11, 3263–3266 (2011).
26. R. C. Shallcross et al., J. Phys. Chem. Lett. 6, 1303–1309
27. K. Zilberberg et al., Adv. Funct. Mater. 21, 4776–4783 (2011).
28. J. Meyer et al., Adv. Mater. 24, 5408–5427 (2012).
29. K. Domanski et al., ACS Nano 10, 6306–6314 (2016).
30. W. Li, W. S. C. Roelofs, M. Turbiez, M. M. Wienk,
R. A. J. Janssen, Adv. Mater. 26, 3304–3309 (2014).
31. C. Huang et al., J. Am. Chem. Soc. 138, 2528–2531 (2016).
32. M. Stolterfoht et al., Energy Environ. Sci. 10, 1530–1539
33. K. Rakstys et al., J. Mater. Chem. A 5, 7811–7815 (2017).
We acknowledge funding from the SAO T at FAU Erlangen-Nürnberg,
which is funded by the German Research Foundation [Deutsche
Forschungsgemeinschaft (DFG)] within the framework of its
“Excellence Initiative.” The work was further supported by the
Cluster of Excellence “Engineering of Advanced Materials.” We
acknowledge financial support from the DFG research training group
GRK 1896 at FAU and from the Bavarian Ministry of Economic
Affairs and Media, Energy and Technology, for the joint projects in
the framework of the Helmholtz Institute Erlangen-Nürnberg for
Renewable Energy (IEK-11) of Forschungszentrum Jülich. We thank
O. Lytken, C. O. Ramirez Quiroz, X. Tang, S. Chen, G. J. Matt,
and A. Osvet for conducting XPS, UPS, UV-Vis absorption, AFM,
electroluminance, and PXRD characterizations and valuable
discussions. Additionally, C.J.B. gratefully acknowledges financial
support through the “Aufbruch Bayern” initiative of the state of
Bavaria, the Bavarian Initiative “Solar Technologies go Hybrid”
(Sol Tech), and the “Solar Factory of the Future” with the Energy
Campus Nürnberg (EnCN). N. L. acknowledges financial support from
the Emerging Talents Initiative at FAU and DFG grant BR 4031/13-1.
All data are presented in the main text and supplementary materials.
Materials and Methods
Figs. S1 to S13
Tables S1 to S4
3 August 2017; accepted 27 October 2017
Published online 9 November 2017
Egg accumulation with 3D embryos
provides insight into the life
history of a pterosaur
Xiaolin Wang,1,2 Alexander W. A. Kellner,3 Shunxing Jiang,1 Xin Cheng,1
Qiang Wang,1 Yingxia Ma,4 Yahefujiang Paidoula,4 Taissa Rodrigues,5 He Chen,1,2
Juliana M. Sayão,6 Ning Li,1 Jialiang Zhang,1,2 Renan A. M. Bantim,6 Xi Meng,1
Xinjun Zhang,1,2 Rui Qiu,1,2 Zhonghe Zhou1,2
Fossil eggs and embryos that provide unique information about the reproduction and early
growth of vertebrates are exceedingly rare, particularly for pterosaurs. Here we report
on hundreds of three-dimensional (3D) eggs of the species Hamipterus tianshanensis from
a Lower Cretaceous site in China, 16 of which contain embryonic remains. Computed
tomography scanning, osteohistology, and micropreparation reveal that some bones lack
extensive ossification in potentially late-term embryos, suggesting that hatchlings might
have been flightless and less precocious than previously assumed. The geological context,
including at least four levels with embryos and eggs, indicates that this deposit was formed by
a rare combination of events, with storms acting on a nesting ground. This discovery supports
colonial nesting behavior and potential nesting site fidelity in the Pterosauria.
Despite recent progress, the general pau- city of pterosaur bonebeds confidently composed of a single species hampers our understanding of several biological ques- tions (1, 2), including their ontogenetic
development and reproductive strategy. Only
a handful of isolated occurrences of eggs and
embryos have been reported so far (2–6). Three-
dimensionally preserved eggs include one from
Argentina (7) and five from the Turpan-Hami
Basin, Xinjiang, northwestern China (8, 9). Ex-
tensive fieldwork in this area has revealed not
only an extraordinary quantity of eggs, but also
the first pterosaur three-dimensional (3D) em-
bryos, providing new information on the embry-
ology and reproductive strategy of these flying
reptiles. The specimens can be attributed to
Hamipterus tianshanensis, the sole species in
this bonebed. The most important section is a
sandstone block (3.28 m2) that yielded 215 eggs,
but up to 300 may be present, because several
more appear to be buried under the exposed
ones (Figs. 1 and 2 and figs. S1 to S13). The eggs
are in an accumulation without a preferential
orientation, clearly showing transport (Fig. 2A).
Their external surface shows cracking and crazing,
and all are deformed to a certain extent, which
indicate their pliable nature (Fig. 2, B to F). Al-
though most eggs are complete, small fissures
resulting from decomposition and compression
during burial must have occurred because all
eggs are filled with sandstone, which ultimately
accounts for their three-dimensionality.
No nests were found, precluding the establishment of clutch sizes. However, the large
number of eggs indicates that they belonged to
several clutches and were laid by different females, which is one plausible explanation for
their moderate size variation (table S1). Furthermore, egg size discrepancy is common within
1Key Laboratory of Vertebrate Evolution and Human Origins,
Institute of Vertebrate Paleontology and Paleoanthropology
(IVPP), Chinese Academy of Sciences, Beijing 100044,
China. 2University of Chinese Academy of Sciences, Beijing
100049, China. 3Laboratory of Systematics and Taphonomy
of Fossil Vertebrates, Department of Geology and
Paleontology, Museu Nacional–Universidade Federal do Rio
de Janeiro, Rio de Janeiro, 20940-040, Brazil. 4Hami
Museum, Hami 839000, China. 5Laboratório de
Paleontologia, Departamento de Ciências Biológicas, Centro
de Ciências Humanas e Naturais, Universidade Federal do
Espírito Santo, Vitória, ES, 29075-910, Brazil. 6Laboratório de
Biodiversidade do Nordeste, Centro Acadêmico de Vitória,
Universidade Federal de Pernambuco, Alto do Reservatório
Street, s/n, 55608-680, Vitória de Santo Antão,
*Corresponding author. Email: email@example.com (X. W.);
firstname.lastname@example.org (A. W.A.K.)