Разработка новых электрон-транспортных материалов для высокоэффективных и стабильных перовскитных солнечных батарей Элнаггар Мохамед Мохамед Рагаб

Краткое описание

Элнаггар Мохамед Мохамед Рагаб.
Разработка новых электрон-транспортных материалов для высокоэффективных и стабильных перовскитных солнечных батарей : диссертация ... кандидата физико-математических наук : 01.04.17 / Элнаггар Мохамед Мохамед Рагаб; [Место защиты: ФГАОУ ВО «Московский физико-технический институт (национальный исследовательский университет)»]. - Москва, 2021. - 110 с. : ил.
Введение диссертации (часть автореферата)на тему «Разработка новых электрон-транспортных материалов для высокоэффективных и стабильных перовскитных солнечных батарей»
Abstract
Hybrid perovskite solar cells (PSCs) have shown a rapid increase in the solar light power conversion efficiency (PCE) within the last few years surpassing recently 25.5 % threshold and coming close to crystalline silicon. However, the progress in improving the stability of PSCs is far from being satisfactory, and therefore, short operation lifetimes represent the main obstacle for the successful commercialization of perovskite photovoltaic technology. Decay in the efficiency of completed p-i-n or n-i-p PSC architectures under light exposure can be caused by tens of different factors. Even when the experiments are performed under an inert atmosphere, which excludes the impact of extrinsic factors, such as oxygen and moisture, the device failure can be induced by degradation of the absorber layer, HTL or ETL materials, absorber/HTL and absorber/ETL interfaces, and interfaces between the chargetransport materials and the electrodes. As such, this thesis is dedicated to the development of advanced electron transport layers (ETLs) for p-i-n perovskite solar cells. ETL is an essential component of PSCs and is responsible for the collection of photogenerated electrons. Optimal ETLs should be chemically inert with respect to the complex lead halides, have minimized LUMO energy level offsets with the conduction band of the absorber material, enable efficient and selective extraction of charge carriers, and provide good isolation of perovskite layer, thus preventing its decomposition. Therefore, we tried to fill this gap by exploring a family of new fullerene derivatives, conjugated polymers, and metal oxides as promising ETL materials for p-i-n PSCs.
In the initial part of the thesis, we discuss the growing evidence that the stability of perovskite solar cells (PSCs) is strongly dependent on the interface chemistry between the absorber films and adjacent charge-transport layers, whereas the exact mechanistic pathways remain poorly understood. A straightforward approach is presented for decoupling the degradation effects induced by the top fullerene-based electron transport layer (ETL) and various bottom hole-transport layer (HTL) materials assembled in p-i-n PSCs. It is shown that the chemical interaction of MAPbb absorber with ETL comprised of the fullerene derivative most aggressively affects the device operational stability. However, washing away the degraded fullerene derivative and depositing fresh ETL leads to the restoration of the initial photovoltaic performance when the bottom perovskite/HTL interface is not degraded. Following this approach, it is possible to compare the photostability of stacks with various HTLs. It is shown that poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)
and NiOx induce significant degradation of the adjacent perovskite layer under light exposure, whereas poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) provides the most stable perovskite/HTL interface.
The second part of the thesis is dedicated to the study of a series of functional fullerene derivatives as suitable ETLs for p-i-n PSCs to enable a stable interface and also improve the device ambient stability (i.e. resistance to moisture). We carried out a systematic study of a family of structurally similar fullerene derivatives as electron transport layer (ETL) materials for p-i-n perovskite solar cells. It is shown that even minor modifications of the molecular structure of the fullerene derivatives have a strong impact on their electrical performance and, particularly, ambient stability of the devices. Indeed, an optimally functionalized fullerene derivative applied as an ETL enables stable operation of perovskite solar cells when exposed to air for >800 h, which is manifested in retention of 90% of the original photovoltaic performance. In contrast, the reference devices with phenyl-C61-butyric acid methyl ester as the ETL degraded-almost completely within less than 100 h of air exposure. Most probably, the side chains of the best-performing fullerene ETL materials are filling the gaps between the carbon spheres, thus preventing the diffusion of oxygen and moisture inside the device.

We also present and discuss the results of a systematic study of other series of fullerene derivatives as promising ETL materials for p-i-n perovskite solar cells. The devices fabricated using new fullerene derivatives demonstrated power conversion efficiencies approaching 17.2%, which is higher than the reference cells assembled using PC61BM, which is a benchmark ETL material (15.9%). The improved photovoltaic performance of the devices incorporating new fullerenes derivatives originated from the decreased nonradiative recombination at the MAPbb/ETLs interface, efficient electron extraction, and full coverage of the perovskite absorber layer. These obtained results feature new functionalized fullerene derivatives as promising ETLs for efficient and potentially stable perovskite solar cells.