Perovskite Solar Cells Fabrication Guide using I101 Perovskite Precursor Ink

This guide describes our recommended fabrication routine for perovskite solar cells using Ossila I101 Perovskite Precursor Ink which is designed to be used with a bottom ITO/PEDOT:PSS anode and a top PC70BM/Ca/Al cathode.

ITO / PEDOT:PSS / CH3NH3PbI3-xClx / PC70BM / Ca / Al

perovskite photovoltaic device
We have achieved an average peak power conversion efficiency of 11.7% which is in line with other literature reports using similar ink formulations [1-3].

 

A complete description of our process routine is shown below. You can also download a one page condensed version for use in clean rooms.

We have also produced a full length video guide for this fabrication routine which includes each step, including substrate cleaning, encapsulation and testing of the devices.

Should you have any queries or technical questions about this perovskite fabrication routine please contact us and we'll be happy to help. For more information and recommended reading on perovskites, please see our article Perovskites and Perovskite Solar Cells.

Equipment Required
Substrate Cleaning
PEDOT:PSS Anode Preparation
Perovskite Deposition
PC70BM Deposition
Cathode Deposition
Device Performance



Process chemicals and consumables required

Processing equipment required

1. Substrate clean: Clean Ossila pre-patterned ITO substrates S171 under a laminar flow hood using our standard cleaning routine: Substrates should be sonicated for 5 minutes in hot (70°C) 1% Hellmanex. Rinse substrates twice in boiling, deionised (DI) water (a dump rinse), followed by a further 5 min sonication in IPA and two final dump-rinses in boiling DI water. Dry substrates using compressed nitrogen.

2. PEDOT:PSS anode preparation: All preparation and spin-coating of PEDOT:PSS should be performed in air under a laminar flow hood. Firstly, filter AI 4083 PEDOT:PSS (M121) using a 0.45 μm PVDF filter. Then dispense 35 μl of the filtered PEDOT:PSS solution using a pipette onto the ITO substrate spinning at 6000 rpm (so-called dynamic dispense) with total spin-time set to 40s. The substrate should now be placed onto a hotplate at 120°C. This process creates a PEDOT:PSS film having a thickness of between 40 and 50 nm. After all ITO substrates have been coated, the hotplate temperature must be reduced to 90°C and the substrates held at this temperature until coating with perovskite precursor. Note that the cathode strip is not wiped at this stage to allow complete and smooth coverage of the substrate by the perovskite in step 3 below.

3. Perovskite deposition: Before beginning this step it is essential that humidity is no higher than approximately 40%. You can see the effects of high humidity on the perovskite films in this video presented by Ossila Research Scientist Darren Watters. Should you require a humidity tester or dehumidifier we'd be happy to provide you with our recommendations; please contact us for this information.

I101 Perovskite precursor ink MAI:PbCl2 (3:1) should be first heated for 30 to 60 minutes at 70°C prior to use and then held at this temperature during the entire deposition process. To coat the perovskite precursor, rapidly transfer the ITO/PEDOT:PSS substrate from the hot plate onto the spin-coater (again in air) and spin it at 3000 rpm. Now dispense 30 μl of I101 ink without delay onto the hot substrate, which should be spun for a total of 30s. This will create a bright-yellow coloured film. Place this substrate back onto the hot-plate (in air) at 90°C.

After you have coated all the substrates with the perovskite precursor (films should still appear a bright-yellow colour), take a dry micro-precision cleanroom swab (product C201) and wipe the cathode strip clean. This removes the perovskite-precursor from the surface. Now place the substrates back onto the hot plate and anneal for a further 90 minutes to fully convert the perovskite precursor into the CH3NH3PbI3-xClx perovskite. After this time, all films should have turned from yellow to grey-brown. Under a microscope, the film should appear as a dense, polycrystalline layer. The video below demonstrates this step.

Preparing perovskite thin films for photovoltaics.

4. PC70BM deposition: Firstly, prepare a solution of PC70BM (M113) at 50 mg/ml in chlorobenzene. This should be placed on a hot-plate at 70°C inside a nitrogen-filled glove-box and stirred for 3 to 5 hours before use. For shorter heating times, filtering the solution with a 0.45 µm PTFE filter (C101) is advised. When you are ready, transfer your perovskite-coated substrates into the glove-box. Use a pipette to dispense 20 μl of the PC70BM solution onto the film surface while it is spinning at 1000 rpm on a spin coater. Spin-coat for a total of 30s to create a PC70BM film having a thickness of 120 nm.

5. Cathode deposition: Devices are now ready to be completed via the deposition of the cathode. At a base-pressure of <10-6 mbar, thermally evaporate a composite of calcium/aluminium cathode (5 and 100 nm respectively) onto the film surface through a pixelated cathode mask (E341) to define the active area of the device. Finally, encapsulate your devices using a glass coverslip (C181) and encapsulation epoxy E131 and then expose to UV radiation (350 nm) for 30 minutes to cure the epoxy. Your devices are now ready to be tested and evaluated using the Ossila Push-Fit Test Board (E371) and measurement aperture mask (E361).


Device performance

We show device characteristics for our best pixel fabricated using our process recipe below in Figure 1, using I101 perovskite ink, batch I101-DCW-001. Here, devices were tested under a standard AM1.5 Solar Simulator following a reverse bias sweep. Here, the best performing device had power conversion efficiency (PCE) of 11.7%, a Voc of 0.96 V, a FF of 73.19% and a Jsc of -16.71 mA/cm2.

I101 Perovskite Ink JV curve
Figure 1: JV curve under AM1.5 irradiation for a PV device based on perovskite ink I101 batch I101-DCW-001. Device characteristics were recorded on a reverse sweep.
I101 Perovskite Ink efficiency graph
Figure 2: Distribution in device efficiencies recorded for a typical process run. Data taken from 5 substrates containing 30 pixels. 10 pixels having low operational efficiency resulting from their proximity to the edge of the device substrate were removed from this analysis.

 


Perovskite Photovoltaic Fabrication Video Guide

 

 

Full length fabrication guide detailing all steps necessary for the fabrication and measurement of perovskite solar cells using Ossila I101 Perovskite Precursor Ink.

References (please note that Ossila has no formal connection to any of the authors or institutions in these references):

[1] Efficient planar heterojunction mixed-halide perovskite solar cells deposited via spray-deposition. A. T. Barrows et al., Energy Environ. Sci., 7, 2944-2950 (2014)

[2] Additive Enhanced Crystallization of Solution-Processed Perovskite for Highly Efficient Planar-Heterojunction Solar Cells. P.-W. Liang et al., Adv. Mater., 26, 3748-3754 (2014)

[3] The Roles of Alkyl Halide Additives in Enhancing Perovskite Solar Cell Performance. Chu-Chen Chueh, et al., J. Mater. Chem. A, (2014) DOI: 10.1039/C4TA05012F