S1

Electronic Supplementary Information

2-Methoxyethanol as a new solvent for processing methyl ammonium lead

halide perovskite solar cells

Koen H. Hendriks, Jacobus J. van Franeker, Bardo J. Bruijnaers, Juan A. Anta, Martijn M. Wienk,

and René A. J. Janssen*

Table S1. Physical characteristics of solvents used for perovskite deposition.

Solvent Boiling Point (°C) Vapour Pressure at 20 °C (Pa)

2-Methoxyethanol (2ME) 124 823

N,N-Dimethylformamide (DMF) 153 360

-Butyrolactone (GBL) 206 200

N,N-Dimethylacetamide (DMAc) 165 176

Dimethylsulfoxide (DMSO) 189 56

N-Methylpyrrolidone (NMP) 203 39

Table S2. Slow sweep J–V characteristics for 2ME triple anion cells annealed for various times.

Anneal Time Voc (V) FF Jsc (mA/cm2) Jsc,sr(mA/cm2) PCE (%)

5 min 0.989 0.793 17.05 16.99 13.32

10 min 0.983 0.791 18.37 18.22 14.18

15 min 0.935 0.788 17.82 18.13 13.35

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2017

S2

Figure S1. AFM height images of the SEM images of methyl ammonium lead triiodide perovskite

layers processed on glass/ITO/PEDOT:PSS. (a) 10 μm × 10 μm, height 500 nm, Rq = 148 nm. (b)

10 μm × 10 μm, height 200 nm, Rq = 62 nm. (c) 5 μm × 5 μm, height 100 nm, Rq = 24 nm. (d) 5

μm × 5 μm, height 50 nm, Rq = 10 nm.

S3

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2-20

-15

-10

-5

0

5

10

Dark Fast up Fast down Slowsweep

Cur

rent

Den

sity

(m

A/c

m2)

Voltage (V)

DMF Single Anion

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2-20

-15

-10

-5

0

5

10

Dark Fast up Fast down Slowsweep

Curr

ent D

ens

ity (

mA

/cm

2)

Voltage (V)

2ME Single Anion

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2-20

-15

-10

-5

0

5

10

Dark Fast up Fast down Slowsweep

Cur

rent

Den

sity

(m

A/c

m2 )

Voltage (V)

DMF Triple Anion

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2-20

-15

-10

-5

0

5

10

Dark Fast up Fast down Slowsweep

Cur

rent

Den

sity

(m

A/c

m2 )

Voltage (V)

2ME Triple Anion

Figure S2. Upwards and downwards fast measurements (0.25 V/s), and slow sweep J–V curves

of the best perovskite cells made from single and triple anion precursors.

S4

0.80 0.85 0.90 0.95 1.00 1.050

5

10

15

20

25

# C

ells

Open-circuit Voltage (V)

DMF TA 2ME TA

0.70 0.75 0.80 0.850

5

10

15

20

# C

ells

Fill Factor

DMF TA 2ME TA

15 16 17 18 19 200

5

10

15

# C

ells

Short-circuit Current Density (mA/cm2)

DMF TA 2ME TA

0 20 40 60 80 100 12013

14

15

16

2ME DMF

Time (s)

Pm

ax (m

W/c

m2 )

0.0

0.2

0.4

0.6

0.8

1.0

App

lied

bia

s (V

)

(b)

Figure S3. Histograms and normal curves of all fabricated devices using 2ME or DMF triple anion

precursor solutions, determined by a fast downward J–V sweep in the solar simulator, (a) Voc, (b)

FF, and (c) Jsc. (d) Maximum power point tracking curves for the best solar cells, showing the

applied bias (dotted line) and Pmax (thick line) measured by the solar simulator.

S5

Figure S4. SEM images of perovskite layers processed on glass/PEDOT:PSS (left), glass/PSSH

(middle), and glass (right) for photoluminescence lifetime measurements. From top to bottom:

2ME single anion, 2ME triple anion and DMF triple anion.

2ME SA PEDOT:PSS PSSH Glass

2ME TA PEDOT:PSS PSSH Glass

DMF TA PEDOT:PSS PSSH Glass

S6

700 720 740 760 780 800 820 840102

103

104

Cou

nts

Wavelength (nm)

2ME SA DMF TA 2ME TA

(a)

0 200 400 600 800 1000

101

102

103

Cou

nts

Time (ns)

2ME SA DMF TA 2ME TA

3.9 ns

225 ns

238 ns

(b)

Figure S5. (a) Photoluminescence emission spectra and (b) photoluminescence decay traces of

perovskite layers on glass processed from 2ME or DMF. The solid lines are the stretched

exponential fits. The lifetimes depicted in the graph are the average lifetimes for the respective

curves. For the single-anion precursor a stretched exponential does not fit that data correctly and

an amplitude average lifetime was determined from a tri-exponential fit.

Table S3. Time resolved fluorescence data fit to a stretched exponential decaya

Precursor Solvent Substrate τc (ns) β < τ > (ns) τave (ns) b

Triple-anion DMF PSSH 618 0.66 828 855

Glass 68 0.40 225 195

2ME PSSH 125 0.57 202 219

Glass 49 0.35 238 183

Single-anion 2ME PSSH 2 0.64 3 3.8

Glass 2 0.93 2 3.9

a c( / )( ) (0) tI t I e where τc is the lifetime, β the distribution coefficient, and

1c( ) ( ) the average lifetime. b Amplitude average lifetime determined from a bi-

exponential (for triple-anion) and tri-exponential (for sing-anion) fits.

S7

0 250 500 750 1000 1250 1500 1750

0

-250

-500

-750

-1000

0.858 V 0.881 V 0.908 V 0.926 V 0.942 V 0.961 V

Z''

Z'

DMF Triple Anion

0 250 500 750 1000 1250 1500 1750

0

-250

-500

-750

-1000

0.891 V 0.915 V 0.943 V 0.961 V 0.977 V 0.999 V 1.016 V

Z''

Z'

2ME Triple Anion

Figure S6. Nyquist plots of impedance data measured at open-circuit conditions at various light

intensities of perovskite solar cells processed from triple anion precursors of (a) DMF and (b) 2ME.

The solid dots are the measured data points, the lines are fits of the medium-frequency arc to an -

Rs(RrecC)- equivalent circuit.

Figure S7. Low magnification cross-section SEM images of perovskite solar cells processed from

2ME and DMF triple anion precursors.

2ME Triple Anion DMF Triple Anion

S8

-0.5 0.0 0.5 1.0 1.51E-6

1E-5

1E-4

1E-3

0.01

0.1

1

10

100

Cur

rent

Den

sity

(m

A/c

m2 )

Bias (V)

DMF Triple Anion 2ME Tiple Anion

Figure S8. Fast downward J-V sweeps in the dark of the DMF and 2ME triple anion processed

cells shown in Table 1 and Figure 2 (thin lines) showing that the 2ME cells have a lower dark

current. The thick lines with symbols are the average dark curves. The fact that not all curves have

a minimum current density at 0 V is likely due to the fast measurement protocol, inducing a

displacement current or it is related to the little hysteresis that is present.