Adding Interstitial Layers For Improved Open-Circuit Voltage in Organic Solar Cells

Adding Interstitial Layers For Improved Open-Circuit

Voltage in Organic Solar Cells

SUNNY WITH A CHANCE OF POWER:

Husna Anwar ’15Arango Lab

Leap Symposium 2013

What’s the big deal?•CO2 levels are at 400 parts per million

(ppm) in the atmosphere –

What’s the big deal?•- at 450 ppm temperatures will rise by 2

°C

What’s the big deal?•Fossil Fuels are a finite resource

What’s the big deal?•Fossil Fuels are a finite resource

Image: National Geographic

Alberta Tar Sands

Why Organic Photovoltaics (PV)Silicon-based panels are bulky, expensive and difficult to produce and install.

Image: Birmingham MailImage: Birmingham Mail

Why Organic Photovoltaics (PV)Silicon-based panels are bulky, expensive and difficult to produce and install.

Organic PV is light-weight, flexible and can be produced in a matter of hours. Image:SoloPower

Image: Birmingham Mail

Image: SoloPower

Image: Birmingham Mail

Image: SoloPower

Why Organic Photovoltaics (PV)

Image: Global Solar

Why Organic Photovoltaics (PV)

Image: Global Solar

Image: Global Solar

Image: Global Solar

Image: Global Solar

Why Organic Photovoltaics (PV)

Image: Global Solar

Image: Global Solar

Image: Global Solar

Image: Global Solar

Image: Global Solar

The Donor/Acceptor Concept

Image: Phoebe Tengdin

Donor Acceptor

The Donor/Acceptor Concept

Image: Phoebe Tengdin

Donor

Acceptor

The Donor/Acceptor Concept

Image: Phoebe Tengdin

1

Photocurrent generation

Electrons

Holes

Voltage and Current•Current is the flow of charge

Voltage and Current•Current is the flow of charge•Voltage is what drives charge to flow

Voltage and Current•Current is the flow of charge•Voltage is what drives charge to flow•Power depends on

both current and voltage

P=IV

Issues with Organic PV•Low efficiency due to low open-circuit

voltage (Voc)

Issues with Organic Solar•Low efficiency due to low open-circuit

voltage (Voc)•Voc is connected to interfacial bandgap

Issues with Organic Solar•Low efficiency due to low open-circuit

voltage (Voc)•Voc is connected to interfacial bandgap

-3.0 eV

-4.9 eV

VOC depends on interfacial bandgap

LUMO

HOMO

P3HT

PCBM

-4.0 eV

-6.5 eV

Deposition methods•Spin-coating

A B C D

Image: Andrea Miranda

Substrate

Materialdropped

Spinning

Deposition methods•Vapor Deposition

A B C

Substrate

MaterialThermal

Evaporator(under

vacuum)

Material evaporates

Coated substrate

Image: Sophia Weeks

Deposition methods•Transfer Printing

PDMS

PCBM

Glass

PEDOT:PSSP3HT

PCBM spin-coated

A B C D

ITO

What we did•Vapor deposition of small molecule with a

wide bandgap

LUMO

HOMO

P3HT

PCBM

Charge recombination

at the interface

What we did•Vapor deposition of small molecule with a

wide bandgap-3.0 eV

-4.9 eV

-3.1 eV

-4.0 eV

-5.7 eV -6.5 eV

LUMO

HOMO

P3HTAlq3

PCBM

very thin interstitial layer of Alq3

Results

dark

light

Results

Voc =0.27 V

Jsc =0.013 mA

Results

Voc =0.44 V

Voc =0.27 V

Jsc =-0.011 mA

Jsc =0.013 mA

Issues•Very low short-circuit current (Jsc)

Issues•Very low short-circuit current (Jsc)•Inconsistent device performance

Issues•Very low short-circuit current (Jsc)•Inconsistent device performance

PCBM film on a PDMS stamp

Issues•Very low short-circuit current (Jsc)•Inconsistent device performance

Surface topography imaged through Atomic Force Microscopy (AFM)

PCBM film on a PDMS stamp

-29 nm

68 nm

5 nm

5 nm

10 nm

0 nm0 nm

What we found out•Alternative energy is essential

What we found out•Alternative energy is essential•Organic PV is a very viable solution

What we found out•Alternative energy is essential•Organic PV is a very viable solution•Adding a small molecule almost doubled

our Voc

What we found out•Alternative energy is essential•Organic PV is a very viable solution•Adding a small molecule almost doubled

our Voc

•We need better Jsc and consistency

What we found out•Alternative energy is essential•Organic PV is a very viable solution •Adding a small molecule

almost doubled our Voc

•We need better Jsc and consistency

•We all want this jacket for when our phones die:

Image: Crunch Wear

Future Work•Vapor deposition of C60 instead of PCBM

for consistency-3.0 eV

-4.9 eV

-3.1 eV

-4.5 eV

-5.7 eV

LUMO

HOMO

P3HTAlq3

C60

-6.2 eV

Buckministerfullerene (C60) can be vapor deposited for uniform films

The people who made this summer awesome…• Professor Alexi Arango,

Kanchi Gashaw and Ednah Louie

• Sarah Byrne, Len and Thomas

• Mount Holyoke College

Image: Alexi Arango