الفهرس 
Introduction and Thesis MotivationOnly 14 pages are availabe for public view
 |  | from | 145 |  |  |
| | | from | 145 | | |
Abstract
English summary.
This thesis discusses different types of semiconductors such as
TiO2, WO3, ZnO, and SnO2 which are used as the electron transporting materials for perovskite solar cells.
The present thesis work aimed at achieving perovskite solar cells
of higher performance and stability with a low-cost fabrication
method and at a better understanding of the energetic alignment
of the band levels of the device layers. To reach these goals, we
have investigated the use of the simple spin coating technique for
layer deposition for the preparation of electron transport layers
with controlled optical, electrical, morphological, and structural
properties. We have investigated the effect of the ETM oxide layer
(WO3, ZnO, TiO2, and SnO2) on the preparation and performance
of PSCs.
We have presented the context of the research on solar cells, with
a special focus on the perovskite solar cells as one of sustainable
energy. In this chapter, we have introduced the structure and the
functioning mechanism of these cells, along with the recent research progress made on the topic showing its advantages and its
stability issue. In the last part of this chapter, we have introduced
our thesis motivation via a comparison of the commonly reported
device with our motivating device.
We focus on SnO2 due to its high carrier mobility and high transparency than other semiconductors via solving the problem of
band gap unalignment with the perovskite layer.
We prepare the SnO2 thin-film via facile low-cost method using a
solution-proceed technique from an abundant precursor with the
addition of CTAB as a directing agent. CTAB has a role in the formation of a network structuring carrying SnO2 particles leading to
high dispersing in the solution and preventing the agglomeration
of the particles leading to a reduction in the particle size to 5-6
nm.
English summary
The reduction in particle size to quantum size reveals the known
phenomena of the quantum confinement effect so, we are successful in tunning the SnO2 band gap and widening the band gap
has occurred.
Synthesized SnO2 films are characterized using XRD and XPS to ensure the formation of the desired pure phase. Also, optical were
investigated to ensure the band gap value and verify carrier transportation. The findings from optical investigations were further
examined by electrical four props to ensure high mobility and low
resistivity of the deposited films.
In all results, We compare the commercial bulk SnO2 with the synthesized one to verify the tunning of the band gaps and raising of
carrier mobility of the deposited films.
We test the fabricated cell using a solar simulator to achieve enhanced power conversion efficiency and we conclude these critical points:-
QD-SnO2 can be prepared via a facile solution process at
300 oC using a CETAB surfactant as a dispersing agent.
Using this method, we could get a pin-hole-free uniform
SnO2 layer which improves the reproducibility of these devices.
Synthesized QD-SnO2 achieves quantum confinement
phenomena with the widening of its band gap resulting in
interfacial and favorable, energy-level tuning with the perovskite absorber layer.
Experimentally, QD-SnO2 has a significant role in the interfacial modification of the interface between the blocking
SnO2 and the perovskite absorber layer leading to better
energy alignment of the device layers, finally achieving
better efficiency and reproducibility.
We have performed systematic experiments to solve the
interfacial issue of SnO2 with the Perovskite interface via
English summary
tuning the sno2 band gap to be energetically aligned with
the perovskite conduction band
The achieved favorable energy level tuning was tested in
perovskite solar cells and resulted in substantially enhanced efficiency with an increase in the average stabilized power conversion efficiency PCE and enhanced reproducibility represented with less standard deviation (
10.67±0.5% ).
We have optimized the power-conversion efficiency of an
n-i-p structured solar cell with QD-SnO2 as an interfacial
layer. The maximum efficiency obtained is 11.76% which
is the highest in the literature using hole-free PSCs.
We have shown that increasing SnO2 annealing temperature can be leading to decreasing in film transparency and
get cracking in the crystal structure leading to depression
in carrier mobilities of these films.
We have also developed a new method to reduce device
cost by replacement of gold electrodes with carbon film
which has a second role in increasing device stability via
the creation of a hydro-repel passive layer on the top of
Perovskite active layer.
We have also developed a modified equivalent circuit
model to understand the change in photovoltaic parameters of perovskite solar cells using a comparison of devices with and without QD-SnO2.
An ultrathin layer of QD-SnO2 with high carries mobility
was inserted at SnO2/CH3NH3PbI3 interface in metal-free
and HTL-free fully air-fabricated PSCs. The QD-SnO2 acted
as superfast electron channels and improved the electron
extraction. Additionally, we found that the optimal crystallization temperature of QD-SnO2 is 300 ℃ to obtain the
highest optical transmittance, superior charge recombination rate, and homogenous pinhole-free films. In addition,
the carbon-based fabricated PSC exhibited very good stability after shelf storage of four months in the humid air.
Our results, therefore, verify that the synthesized QDSnO2 at low temperature is an excellent additive ETL
English summary
material for stable and high-performance PSCs. Furthermore, the low-temperature process is compatible with the
roll-to-roll manufacturing of PSCs on flexible substrates
which will reduce the cost of fabrication as well.
Publications:
‘Solution-processed quantum dot SnO2 as an interfacial electron
transporter for stable fully-air-fabricated metal-free perovskite
solar cells ‘Journal of Materiomics,Volume 8, June 2022,
https://doi.org/10.1016/j.jmat.2022.06.001 with cite score of 9.6
and impact factor 8.5.
Rabie M. Youssef, A.M.S. Salem, Ahmed Shawky, Shaker Ebrahim,
Moataz Soliman, Mohamed S.A. Abdel-Mottaleb, Said M. El-Sheikh.
Conferences:
2
nd International Conference on Materials science and Engineering (ICMSE-2019),Cairo, Egypt;
Mar.2019 : Article presentation, Fabrication of ambient air
SnO2/mesoporous-TiO2 Perovskite solar cell ; Rabie.M.Youssef,
Aliaa Salem, Said M.El-Sheikh, Moataz Soliman, Shaker Ebrahim, Mohamed S A Abdel-Mottaleb.