A Review: Organic Tandem Cells

A Review:
ORGANIC TANDEM CELLS
Abstract
In these review theoretical considerations trying to address the would-be of tandem photovoltaic
cells, experimental realizations, basic design considerations to ensure effective and efficient
material combinations and conclusion are presented.
1. Introduction
Over 80% of the world’s consumption of energy is provided by non-renewable sources. Non-
renewable sources of energy compose mainly the fossil fuels like coal, gas and oil. In the process
of the fossil fuels producing energy for machines, motor vehicles and industrial and domestic
heating, they produce a lot of carbon dioxide which is the major of climate change. (Choy, 2012)
(Qiao, 2017) Carbon dioxide causes greenhouse effect due to destruction of ozone layer (O3). In
addition these energy sources are increasingly becoming more and more expensive. Hence, a
need for the world to shift its focus to the renewable sources of energy has become inevitable.

1.0 figure: Showing the concentration of carbon (IV) oxide overtime until 2016 (Horstmeyer,
2011)
Renewable sources of energy have thus become a major focus of worldwide new energy
strategy. This is because they represent a viable alternative in reducing overdependence on fossil
fuels, and a long term strategy in ensuring renewable sources of energy become the major source
of energy. (Rim, 2010)
There are various sources of renewable energy among the wind power, biomass, solar energy and
fuel cells. We know that renewable sources of energy have their own shortcomings and their
dependence, and total overhaul of the energy strategy won’t solve all environmental problem and
may not stabilize world climate. (Soga, 2006) But renewable energies represent viable options to
solving the present and foreseeable energy crises. The earth receives huge amounts of energy
from the sun that is approximated to 4 yottaJoules. Since the world consumption in 2013 was
0.000567 yottaJoules, it means that our consumption is dwarfed by the energy received from the
sun. Thus earth receives enough energy to fulfil world demand.
Due to increased exploration of renewable energies viability coupled with harming effects of
fossil fuels our attention has shifted to carbon free energy, photovoltaic technology. (Choy,
2012) In recent years a number of publications and journals have detailed the great strides
scientists and researchers have done in dealing with solar electricity and solar cell. (Choy, 2012)
The advancements in technology of solar cells increased steadily starting in the 1980s.This was
possibly caused by the crisis in oil industry that occurred in 1973. (Chen, 2011) (Formann, 2016)
The latest stead rise in the production of solar electricity and PV industry was witnessed in the
last decade. (Hsin-Fei, 2013)This rise might have been triggered by changing climatic conditions
caused by global warming. Since 2006 the solar technology has been advancing each year at the
rate of at least 40%.
Organic solar cells (OSC) are photovoltaic devices working on knowledge based on organic
semiconductors. OSC are still in developmental stage but are predicted to become major
candidate for PV industries. Examples include organic tandem cells and single junction cells.
Some of th e factors which favour them include ease of processing, mechanical flexibility and

low cost of large scale production
2.0 figure: showing production of PV cells since 2006 (World, 2019)
The graph above shows the impressive figures posted and recorded for years starting 2006 up to
2013. They show how the production of PV cells has been evolving greatly.
Our aim we aim to review current trends regarding organic tandem photovoltaic cells, existing as
well as discuss major experimental calculations and results and later on make some design
parameters for effective and efficient material combinations for manufacture of organic tandem
cells. (Bisquert, 2017)
2. Theoretical considerations
Organic Tandem Cells
In 1961, Shockley and Quieisser did some calculations in trying to evaluate thermodynamics
efficiency conversion of a solar energy cell. The parameters that they took into account are:
 Energy from Photons is bigger than a band packet of the proactive materials which are
absorbed and lead to contribution to conversion in photovoltaic. (Ikhmayies, 2018)
 Creation of carriers which are Hot on photon absorption decrease due to band conduction
of photoactive substances; this is known as thermalization. (Tress, 2014)
Thus the maximum efficiency is given by;
h ( EG )=¼ JSC( EG)×VOC(EG )× FF
But Voc observed in a device differs by 0.3eV due to losses. As such Voc obeys the empirical
formula of equation;