Solution-processed organic-inorganic halide perovskites have demonstrated immense potential in photovoltaic applications, but scaling up the perovskite solar cell production is faced with big challenges. Inkjet printing is a facile scalable approach to deposit thin films due to its cost-effectiveness and near unity material utilization ratio, which makes it worthy of exploration from the perspective of both environmental protection and economic benefit. The objective of my thesis research is to develop the inkjet printing technology and to understand the underlying mechanisms for efficiently fabricating perovskite thin films and solar cells.

Chapter 1 is dedicated to the background of organic-inorganic halide perovskite. Their working principles and properties are reviewed. The...[ Read more ]

Solution-processed organic-inorganic halide perovskites have demonstrated immense potential in photovoltaic applications, but scaling up the perovskite solar cell production is faced with big challenges. Inkjet printing is a facile scalable approach to deposit thin films due to its cost-effectiveness and near unity material utilization ratio, which makes it worthy of exploration from the perspective of both environmental protection and economic benefit. The objective of my thesis research is to develop the inkjet printing technology and to understand the underlying mechanisms for efficiently fabricating perovskite thin films and solar cells.

Chapter 1 is dedicated to the background of organic-inorganic halide perovskite. Their working principles and properties are reviewed. The objectives of my thesis are elaborated.

Chapter 2 is dedicated to the fabrication approaches for perovskite thin films. In particular, I further elaborate the advantage of inkjet printing technology and current challenges to employ it to deposit perovskite thin films.

Chapter 3 describes all the characterizations methods used, including characterizations for perovskite precursors (inks), perovskite thin films and perovskite solar cells used in the further chapters.

In Chapter 4, I have demonstrated that high-quality CH₃NH₃PbI₃ patterns, including dots, uniform lines, and compact films, by inkjet printing under ambient condition. The dynamics of perovskite droplets including spreading, coalescence and evaporation have been studied. Crystallization processes of the perovskite during the inkjet printing processes have been studied. Basing on these studies, I have achieved a champion power conversion efficiency (PCE) of 16.6% for the ambient printed devices.

Exploration of novel perovskite compositions has a strong demand for high throughput fabrication. In Chapter 5, I have developed a high throughput approach to deposit mixed perovskite thin films by inkjet printing. Twenty-five FA_xMA_1-xPbI_yBr_3-y perovskite films have been fabricated via high throughput inkjet printing. Basing on these perovskite films, I have built a properties database (including crystal phases, bandgaps, and PL lifetimes) to screen optimal perovskite composition (MAPbBr_0.75I_2.25).

Perovskite films with similar optimization levels can largely enhance the effectiveness composition screening based on comparison of their properties. In Chapter 6, thirty mixed tribromide perovskite films including FA_xMA_1-xPbBr₃, MA_xCs_1-xPbBr₃, and Cs_xFA_1-xPbBr₃ have been fabricated via high throughput inkjet printing. The printing conditions under which printed films shows similar optimization level have been examined. Optimal perovskite composition (FA_0.4MA_0.6PbBr₃) has been screened out for further high-photovoltage solar cells fabrication via spin-coating.

All-inorganic carbon-based perovskite solar cells with high efficiency and excellent stability are promising for commercialization. In Chapter 7, I have developed a two-step inkjet printing approach to deposit high-purity inorganic CsPbBr₃ layers. Upon optimization of the print process for CsPbBr₃ layers, I have achieved a efficiency of 8.37% with a V_oc of 1.49V for the printed all-inorganic carbon-based perovskite solar cells.

Based on these studies, I have demonstrated that inkjet printing can be a facile and low-cost approach to fabricate high quality perovskite thin films. For organic-inorganic perovskite composition, it can be utilized to exploration of novel composition. For inorganic perovskite compositions, it can be utilized to fabricate high-performance device.