EE-611 Lab Report

Fabrication and Characterization of Organic

Solar cell

Submitted By:-

Birendra Kumar Birua

(13104029)

M-Tech VLSI

Date 27-Apr-14

Fabrication and Characterization of Organic Solar Cell

Device Structure

ITO/ZnO/P3HT:PCBM/MoO3/Au

Figure 1 Device Structure

Pre Requisite:

ITO (Indium Tin Oxide) coated patterned glass Substrates.

Chemicals / Elements Required

Liquid Ammonia : For RCA solution

Acetone: Used to clean the vacuum system, boat etc., Au wire etc.

Deionised Water (DI): For wet processing.

ZnO: ZnO nanoparticles used to reduce resistance between ITO and

active layer, and also help in enhancing Voc of solar cell.

P3HT: PCBM: This is used as active layer for the organic solar cell.

MoO3: used as a cathode buffer layer.

Gold: Gold is used for second electrode and having work-function

~5.0eV.

Miscellaneous items: Tissue papers, plastic gloves, hair net and mouth

masks, cleaning Brush, Beakers, Petridis, Drier, and Syringe etc are also

needed.

Apparatus Required

Substrate Holder: Used to hold the substrate as shown in fig-3.

Vacuum Coater: Is used for deposition of desired thickness of Pentacene and Gold in vacuum

having vacuum of 10-6

mbar, shown below in fig-4 and fig-5 (made by Hind HIVAC Vacuum

systems).

Desiccators: Used to protect the samples from contaminations and degradation due to

atmospheric conditions shown in fig-6.

Ultrasonicator: Used for Ultrasonically Cleaning the Substrates so as to remove tiny suspended

particles shown in fig-7.

Figure 2 DI Water Apparatus

Spin Coater: Used for spin coating purpose shown in fig-8.

Steps involved in fabrication of Organic Solar Cell I. Substrate cleaning and ITO patterning.

II. RCA cleaning of substrate.

III. ZnO spin coating and oven annealing.

IV. P3HT:PCBM spin coating and vacuum annealing.

V. MoO3 deposition.

VI. Gold thermal deposition.

VII. Encapsulation and Contact making using silver paste.

I. Substrate cleaning and ITO patterning

The glass substrate is cleaned with soap and DI water with the help of brush then the substrate is put in the

substrate holder and rinsed well thoroughly in the DI water. The process is repeated 3-4 times.The substrate is

put in DI water with the help of substrate holder in a beaker and the beaker was put in ultrasonicator for 5

minutes as shown in fig-7 above. And repeated 3-4 times changing beaker DI water.

II. RCA Cleaning

RCA Solution Preparation

a. RCA solution is prepared by mixing DI water, H2O2 and NH3 in the ratio of 5:1:1 (300ml: 60ml:

60ml) in a clean beaker.

b. This prepared solution is now heated at 60-65oC for 20 minutes on the hot plate inside the fume hood.

c. A cleaned thermometer is immersed in this solution to measure the temperature.

Figure 3 Substrate Holder Figure 4 Vacuum Coater Figure 5 Inside Box Coater

Figure 6 Desiccator

Figure 3 Substrate Holder

Figure 7 Ultrasonicator Figure 8 Spin Coater

ITO coated substrate is now immersed in this prepared RCA solution for 20 minutes at 60-65oC. After

removing from this RCA solution the substrates are again cleaned with DI water. Again the substrate in

substrate holder is dipped in a beaker containing DI water and is put on a UV cleaning machine for 5 minutes.

Then the substrate is removed from the UV machine and dries the same using drier so as to dry out DI water

droplets. Lastly the substrate in the drying oven so as to evaporate the DI water completely for 20 minutes at

1200-140

0C.

III. ZnO coating

A coating of ZnO layer is done by spin coater shown in fig-8 at a rotation speed of 2000 rpm for 1 minute; we

get a uniform layer of ZnO spread all over the substrate which dries within 45 sec during spin coating. We can

get different thickness of layer by varying rotation speed of spin coater. Then the substrate is kept in oven at a

temperature of 2500C for 15 minutes, which hardens ZnO layer above ITO.

IV. P3HT:PCBM coating and annealing

P3HT:PCBM Solution Preparation

a. The P3HT:PCBM solution is made in the following composition:

P3HT: PCBM: Chlorobenze: 10gm: 10gm: 1ml

b. The solution is put on a magnetic stirrer for stirring for 8-12 hours.

The solution is filtered using a 0.4 micron size paper filter using a metal stand. The P3HT:PCBM blend is spin

coated at 1000 rpm for 1 minute as shown in fig-9. The metal masks were placed and substrates were fixed on

the substrate holder and the substrate holder was placed into vacuum. Also we placed some amount of Au in

boat before closing the chamber of vacuum system. Then the P3HT: PCBM coated substrates were annealed

at 1300C in vacuum. The vacuum system took 5-6 hours for cooling.

c.

V. MoO3 deposition

MoO3 layer is deposited after annealing of P3HT:PCBM at a rate of 0.1-0.2/sec. Thickness of MoO3 layer

6nm, this step takes 5-10 minutes but a precise deposition is needed.

VI. Au deposition

The thickness was measured using the DTM. Before starting the evaporation of Au, the following values were

set: Density =19.30 g/cm3, Acoustic Impedance = 23.18

Gold deposition of 100 nm was done on the substrate at a rate of 0.1-0.5 /sec.

.

Figure 9 Spin coating of P3HT

VII. Encapsulation and Contact making

The devices were encapsulated using glass substrates in nitrogen ambient. Epoxy was used to seal the glass

cover over device substrate and it was put under UV treatment for 10 minutes so that epoxy gets hardened.

Silver paste and thin Al wires were used for contact making. The Amyl acetate is used to dilute the silver

paste.

Characteristics of the device

I. Input Characteristics in dark

Figure 10 Forward I-V Characteristics in dark (device C2)

II. Input Characteristics in Light

Figure 11 Forward I-V Characteristics in light (device C2)

III. Voc and Isc

Figure 12 Zoomed View of I-V curve (Device C2-R22)

IV. Power Curve

Figure 4 Power Curve (Device C2-R22)

Voc 0.4 V Isc 0.616 mA Vm 0.28 V Im 0.41 mA Pmax 0.1148 mW FF 0.466 Efficiency(%) 0.7175 %

=

% =

100 ; = 1000 2 0.004 0.004 2