S1
Supporting Information
Impact of the Growth Conditions of Colloidal PbS Nanocrystals on Photovoltaic
Device Performance
Huiying Fu,† Sai-Wing Tsang,† Yanguang Zhang,† Jianying Ouyang, ‡ Jianping Lu,*, † Kui Yu*, ‡ and Ye Tao*, †
Institute for Microstructural Sciences,† Steacie Institute for Molecular Sciences, ‡ National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
E-mail: Jianping.Lu@nrc-cnrc.gc.ca; Kui.Yu@nrc-cnrc.gc.ca; Ye.Tao@nrc-cnrc.gc.ca;
Table of contents
Absorption and PL spectra of the PbS nanocrystals S2
XPS spectra of the as-synthesized PbS nanocrystals S3
TEM images of cross-linked PbS nanocrystals with 1,3- benzenedithiol S4
FTIR spectra of cross-linked PbS nanocrystals with 1,3- benzenedithiol S5
Nanocrystal mono-dispersivity on PV device performance S6
PbS nanocrystal PV device performance at different light intensities S7
S2 Absorption and PL spectra of the PbS nanocrystals
Figure S1. Absorption and PL spectra of the PbS nanocrystals grown at an OA concentration in ODE of 0.51 mol/kg after growth at 90 °C for 3 min.
S3 XPS spectra of the as-synthesized PbS nanocrystals
1000 800 600 400 200 0 0 20 40 60 80 100 120 140 In te n s it y ( k C P S )
Bonding Energy (eV)
P b 5 d P b 5 p P b 5 p 1 /2 P b 4 f7 /2 P b 4 f5 /2 S 2 p S 2 s C 1 s P b 4 d 5 /2 P b 4 d 3 /2 O 1 s P b 4 p 3 /2 P b 4 p 1 /2 P b 4 s O K L L (a) 152 148 144 140 136 132 0 2 4 6 8 10 12 14 16 18 20 P b 4 f In te n s it y ( k C P S )
Binding Energy (eV) (b) P b 4 f PbS PbS 172 170 168 166 164 162 160 158 156 154 4.0 4.5 5.0 5.5 6.0 6.5 In te n s it y ( k C P S )
Binding Energy (eV)
S 2 p (c) 300 295 290 285 280 275 4 6 8 10 12 14 16 18 20 22 In te n s it y ( k C P S )
Binding Energy (eV)
C 1 s C 1s C-C, C-H C 1S C=O (d)
Figure S2. (a) XPS survey spectra of the as-synthesized PbS nanocrystals. (b), (c) and (d) High resolution of Pb 4f, S 2p and C 1s spectra of PbS nanocrystals.
S4
TEM images of the cross-linked PbS nanocrystals with with 1,3-benzenedithiol
Figure S3. (a) TEM and (b) HRTEM images of PbS nanocrystals cross-linked with 1,3-benzenedithiol.
Thiols strongly binds with the Pb atoms on NC surface. After cross-linking, the inter-nanocrystal distance is reduced from 2 nm to 0.6 nm. The small 1,3- benzenedithiol can tightly crosslink NC thin films and facilitate the layer-by-layer process. Compared with 1,4- benzodithiol, 1,3-benzodithiol can bring NCs into closer contact. Compared with 1,2-ethylene dithiols (EDT), the lower vapour pressure of 1,3-BDT makes it easier to be handled during the fabrication processes.
S5
FTIR spectra of cross-linked PbS nanocrystals with 1,3- benzenedithiol
Figure S4. FTIR spectra of a PbS nanocrystals thin film (15 nm) spin cast on Si substrate before (oleic acid capped) and after (1,3-Benzenedithiol capped) cross-linking. After cross-linking the intensity of C-H (2856 cm-1 and 2925 cm-1) vibration arising from oleic acid is largely reduced. Instead, three new absorption peaks were observed at 1558, 1540, and 1454 cm-1, indicating the pesence of 1,3-benzenedithiol.
S6
Nanocrystal mono-dispersivity on PV device performance
Figure S5 The fill-factor (FF) and power conversion efficiency (PCE) of Schottky-type PbS nanocrystal PV devices fabricated with nanocrystals with different first excitonic peak width (w). The peak widths were obtained by fitting the first excitonic peak with Gaussian functions. The first excitonic peak position of different samples were chosen at 1000±50 nm.
S7
PbS nanocrystal PV device performance at different light intensities
Figure S6 (a) J-V characteristics, (b) VOC and FF, (c) JSC, and (d) PCE of Schottky-type PbS
nanocrystals device performance at different light intensities of AM 1.5G illumination. The linear dependence of JSC on excitation density suggests geminate recombination as the major recombination
S8
Summary of the photovoltaic performance for the PbS nanocrystals with different storage time
Table S1. Summary of the photovoltaic performance of ITO/PbS-BDT/LiF/Al devices based on PbS nanocrystals storied in the glovebox for different time. PbS NCs were from the same batch.
PV cell performance Thickness of PbS NCs (nm) JSC (EQE) (mA/cm2) VOC (V) FF (%) PCE (EQE) (%) As-synthesized PbS NCs 10.85 0.55 59 3.5 1 month 11.33 0.57 58 3.8 2 months 11.19 0.55 59 3.6 Storage time in the glovebox 4 months 110 to 115 11.23 0.55 57 3.5