Supplementary information for

Efficient and stable perovskite solar cells thanks to dual functions of oleyl amine-coated PbSO4(PbO)4

quantum dots: defect passivation and moisture/oxygen blocking

Chong Chen,a*§ Fumin Li,a§ Liangxin Zhu,a Zhitao Shen,a Yujuan Weng,a Qiang Lou, a Furui Tan,a

Gentian Yue, a Qingsong Huang,b* Mingtai Wangc*

aHenan Key Laboratory of Photovoltaic Materials, Henan University, Kaifeng 475004, P.R.China,

bSchool of Chemical Engineering, Sichuan University, Chengdu 610065, P.R.China

cInstitute of Applied Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences,

Hefei, 230031, PR China

E-mail: chongchen@henu.edu.cn (C. Chen), qshuang@scu.edu.cn (Q. Huang), mtwang@ipp.ac.cn (M.

Wang).

1. First-principles calculations

Electronic structure calculations are performed with the density functional theory as implemented in

the Vienna ab initio simulation package,1,2 employing projected augmented wave potentials to describe

the atomic core electrons and a plane wave basis set with a kinetic energy cutoff of 450 eV to expand

the Kohn−Sham electronic states. For the exchange and correlation functional, the generalized gradient

approximation (GGA) in the Perdew–Burke–Ernzerhof (PBE) format was used.3 The

CH3NH3PbI3/PbSO4(PbO)4 interface was simulated by 5 atomic layers CH3NH3PbI3 (001) contacted

with a PbSO4(PbO)4 (100) slice of 7.3 Å, and a vacuum thickness of 20 Å was added along the z

direction. To give a better lattice matching between CH3NH3PbI3 and PbSO4(PbO)4, the surface unit cell

of CH3NH3PbI3 (001) were rotated by 45˚ and enlarged by 21/2 times. The periodic slab model includes

160 atoms in total. The Brillouine zone was sampled in (3 × 3 × 1) and (5 × 5 × 1) Monkhorst–Pack 4 k-

point meshes in structure relaxations and DOS calculations, respectively. The DFT+D2 scheme

proposed by Grimme5 was adopted to include the dispersion interactions. During structural

optimization, the bottom 3 atomic layers of CH3NH3PbI3 were fixed, and all the other atoms were fully

relaxed until the atomic forces are smaller than 0.05 eV Å-1. At last, the wavefunction was analyzed by

virtue of the VASPKIT code.6

Similar numerical simulation was performed for the oleylamine adsorbed on the CH3NH3PbI3

surface. A 3 × 1 CH3NH3PbI3 (001) surface unit cell with 6 atomic layers was used, and a vacuum

thickness of 20 Å was added along the z direction. The Brillouine zone was sampled in (1 × 3 × 1)

Monkhorst–Pack4 k-point meshes. The dispersion correction was also include by the DFT+D2 scheme5.

To reduce computational cost and mimic the bulk influence, the bottom 4 atomic layers of CH3NH3PbI3

were fixed during structural optimization, and other atomic layers and the oleylamine molecule were

relaxed until the atomic forces are smaller than 0.05 eV Å-1.

References:

1. G. Kresse, J. Hafner, Phys. Rev. B 1993, 47, R558

2. G. Kresse, J. Furthmuller, Phys. Rev. B 1996, 54, 11169

3. J. P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett., 1996, 77, 3865.

4. H. J. Monkhorst, J. D. Pack, Phys. Rev. B: Solid State, 1976, 13, 5188.

5. S. Grimme, J. Comput. Chem., 2006, 27, 1787.

6. V. Wang, N. Xu, VASPKIT: A Pre- and Post-Processing Program for the VASP Code. http://vaspkit.sourceforge.net

2. Supplementary Figures

Figure S1Fig. S1 XRD patterns of the PbSO4(PbO)4.

Figure S2

Fig. S2 The low-magnification (a) and high- magnification (b) TEM images of PbSO4(PbO)4 QDs after ultrasonic dispersion treatment.

Figure S3 Fig. S3 XRD patterns of the CH3NH3PbI3 films with and without the PbSO4(PbO)4 QDs in the regions (a)10.6º-59º, (b)13.0º to 15.0º, and (c) 28.0º to 30.0º.

Figure S4

Fig. S4 AFM images (a) FTO/cp-TiO2/mp-TiO2/CH3NH3PbI3 and (c) FTO/cp-TiO2/mp-TiO2/ CH3NH3PbI3/PbSO4(PbO)4, the corresponding 3D surface plot images of (b) FTO/cp-TiO2/ mp-TiO2/CH3NH3PbI3 and (d) FTO/cp-TiO2/mp-TiO2/CH3NH3PbI3/PbSO4(PbO)4.

Figure S5Fig. S5 UV-Vis absorption spectra of (a) pure CH3NH3PbI3 and CH3NH3PbI3/PbSO4(PbO)4 films and (b) pure PbSO4(PbO)4 QDs.

Figure S6

Fig. S6 (a) UV–vis absorption spectra of pure CH3NH3PbI3 and CH3NH3PbI3/PbSO4(PbO)4 films. (b) Normalized photoluminescence decay dynamics of the FTO/cp-TiO2/mp-TiO2/CH3NH3PbI3 and FTO/cp-TiO2/mp-TiO2/CH3NH3PbI3/PbSO4(PbO)4 probed at 775 nm after excitation at 515 nm (The solid lines are fitted results). The laser was incident from the PbSO4(PbO)4 QDs layer.

Figure S7

Fig. S7 The water contact angle: (a) ITO/TiO2/CH3NH3PbI3 and (b) ITO/TiO2/ CH3NH3PbI3/PbSO4(PbO)4 films

Figure S8Fig. S8 (a) Electrochemical impedance spectra (EIS) of the device under illumination100 mW/cm2 with zero applied potential, (b) Equivalent circuit for fitting Data.

Table S1 The fitting parameters for measured EIS results with different device.

Devices RS (Ω cm2)

RCT1

(mA cm-2)RCT2

(mA cm-2)CPE1(nF cm-2)

CPE2

(μF m-2)CH3NH3PbI3 67.03 1192.01 1057.01 38.41 28.05CH3NH3PbI3/PbSO4(PbO)4 64.97 639.70 962.01 27.64 86.11

Figure S9Fig. S9 UPS spectra of the CH3NH3PbI3/PbSO4(PbO)4 film.