One-Step Solution Deposition of Tin-Perovskite onto a Self-Assembled Monolayer with a DMSO-Free Solvent System

We show for the first time DMSO-free tin-based perovskite solar cells with a self-assembled hole selective contact (MeO-2PACz). Our method provides reproducible and hysteresis-free devices with MeO-2PACz, having the best device PCE of 5.8 % with a VOC of 638 mV.


Chemicals:
We purchased water-free PEDOT-complex dispersion in toluene (HTL3) from Clevios TM .Formamidinium iodide was purchased from Dyenamo.MeO-2PACz (Product Number: D5798) was purchased from Tokyo Chemical Industry (TCI).Silver shot (1-5 mm, 99.9%) was purchased from Alfa Aesar.C60 was purchased from CreaPhys.All the other chemicals were purchased from Sigma Aldrich and used as received.

Device Fabrication:
The patterned ITO substrates (2.5x2.5cm 2 , Kintec, 10 Ohm per square) were washed with in Hellmanex 2% deionised water (DI) solution, DI water, acetone, and ethanol for 15 minutes at 40 °C sequentially.After that, the well-dried ITO substrates were treated in a UV-ozone cleaner for 30 min at 35 °C.Once completing UV-ozone treatment, the cleaned ITO substrates immediately are transferred to N 2 filled glovebox.It is worth mentioning that all of the device fabrication steps were carried out in a highly pure N 2 -filled glovebox (glovebox temperature was around 24 °C), and glovebox has never been exposed to Dimethyl sulfoxide (DMSO).Solvent regeneration frequently was applied to avoid solvent vapour.The monolayer of MeO-2PACz is deposited from fresh 1 mM stock solution which was prepared in absolute ethanol.100 μL of MeO-2PACz solution is statically poured on a pre-cleaned ITO substrates, after 5 sec (give time to it for attaching ITO coated substrate) the solution spun at 6000 rpm for 30 seconds.Then, the MeO-2PACz coated ITO substrates were annealed at 150 °C for 15 min.The freshly prepared diluted PEDOT-complex (1:4 v:v in dry toluene) was deposited/annealed subsequently as in our previous work. 1The stock solutions of SnI 2 (1.2 M) and EDAI 2 (1 M) were prepared in a DMSO-free solvent system from N,N-diethylformamide:N,N'dimethylpropyleneurea (DEF:DMPU, 1:6, v:v) and left overnight in a thermoshaker at 20 °C before preparing the perovskite final solution.The FASnI 3 solution (1.2 M in 6:1 DEF:DMPU, with 10% over stoichiometry of SnI 2 and eventually 5% EDAI 2 ) was spun at 500 rpm for 5 seconds and 4000 rpm for 40 seconds.After 21 seconds, 100 μL of diethyl ether (DEE) were dropped on the spinning substrate to induce the perovskite crystallisation.The film was annealed at 100 °C for 30 minutes.As electron selective contact, C 60 (50 nm) and BCP (7 nm) were subsequently evaporated at a 10 -6 mbar vacuum level with a deposition rate between 0.1 and 0.3 Å s -1 .Following, silver was evaporated through a shadow mask at a rate of 0.1 Å s -1 up to 5 nm, increasing to 0.3 Å s -1 up to 10 nm and then at 1 Å s -1 up to 150 nm.The completed device area is around 0.17 cm 2 .The devices always were stored in a glovebox before measuring.

Contact Angle Measurement:
The water contact angle measurements were performed with a Kruss Drop Shape Analysis System DSA25 outside the glovebox.The droplet volume was between 1 and 2 µL.

X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM):
Film morphology was characterized using a MIRA3 TESCAN microscope with an accelerating voltage of 5 kV.XRD patterns were recorded with a Bruker D8 Advance diffractometer with Bragg-Brentano geometry equipped with a Cu Ka1(l= 1.544060 Å) anode, operating at 40 kV and 40 mA.All the diffraction patterns were collected at room temperature, with a step size of 0.05 in symmetric scan reflection mode and an acquisition time of 1 s.XRD patterns were recorder on thin films in an inert environment by means of a Bruker air tight specimen holder with dome like X-ray transparent cap, for environmentally sensitive materials.
Current Density-Voltage Scan (J-V): J-V curves were measured with a commercial apparatus (Arkeo-Ariadne, Cicci Research s.r.l.) based on a ring of 12 LEDs ranging from 300 to 1000 nm and calibrated to fit class A and a 4-wire source meter.

Incident Photon to Current Efficiency (IPCE):
The IPCE spectrum was measured with a commercial apparatus (Arkeo-Ariadne, Cicci Research s.r.l.) based on a 300-Watt xenon lamp, able to acquire a spectrum from 300 to 1000 nm.

Figure S5. Corresponding incident photon current efficiency curves which show integrated current density in agreement with values from the J-V curves of PEDOT and MeO-2PACz based
Sn-PSCs.

Figure S2 .
Figure S2.Device performance statistics of a total 20 devices based on various deposition speeds of MeO-2PACz monolayer from fresh devices.

Figure S4 .
Figure S4.Forward and reverse scan statistics of device performance from PEDOT and MeO-2PACz based Sn-PSCs after two weeks.

Table S1 .
Photovoltaic parameters of PEDOT-based Sn-PSCs with forward (FW) and reverse (RV) scan after two weeks.

Table S2 .
Photovoltaic parameters of MeO-2PACz-based Sn-PSCs with forward (FW) and reverse (RV) scan after two weeks.