全球環境和資源對未來能源需求和安全的高度關注將不斷增加，這取決於可獲取、可持續和可擴展的能源技術的發展。在過去的幾十年裡，學術界和工業界作一直致力於與聚合物相關的最先進的小分子有機物的研究，因為它們具有許多優點，例如高純度和結晶度、明確的分子結構、不存在端基污染物 、高流動性和批次間重現性。
最成功的二維（2D）電子供體單元, benzo[1,2-b:4,5-b´]dithiophenes (BDTs), 已成為聚合物太陽能電池和小分子有機太陽能電池的熱門結構單元材料，由於高共面性 ，π-π堆積，高遷移率和增強的溶解度。BDT衍生物給供電子基團的橫向柔性側鏈操縱即TB-BDT6T被ethynylthenyl取代, TS-BDT6T被thenylthio取代, 和TT-BDT6T被alkyl thienothiophenes取代。實驗結果表明，在不改變封端受體（氰基乙酸酯）部分的情況下橫向摻入柔性側鏈使基於 BDT 的小分子能夠成功地改善光電特性。與 TB-BDT6T 相比，TS-BDT6T 和 TT-BDT6T 在固態下表現出良好的堆積。此外，TS-BDT6T 和 TT-BDT6T 表現出優異的電荷傳輸特性和有序的分離網絡分佈，從而提高了功率轉換效率。
不對稱苯並[2,1-b:-3,4-b':5,6-b″]三噻吩（不對稱BTT）中擴展的芳香核提供了完全的平面性，從而有利於分子間的π-堆疊和電荷傳輸。不對稱 BTT 單元用作中心核心，其上附加了各種供體基團，咔唑 (BTT-CB)、噻吩並噻吩 (BTTFT)、三苯胺 (BTT-TPA) 和二噻吩 (BTT-TT)。與其他三種空穴傳輸材料相比，BTT-TT具有良好的結晶度和優異的空穴遷移率，並且在覆蓋鈣鈦礦活性層時形成了光滑均勻的表面。BTT-TT作為空穴傳輸材料的最高功率轉換效率為18.58%，儲存700小時以上穩定性良好。
金屬鹵化物鈣鈦礦薄膜的晶界和表面缺陷作為非輻射複合中心，降低鈣鈦礦太陽能電池的性能和/或穩定性。核扭曲四氯苝二亞胺 (ClPDI) 衍生物（n 型小分子）含有各種末端基團（正丁基 (ClPDI-C4) 、二甲基氨基丙基 (ClPDI-OmeA) 和氨基丙基 (ClPDI-DPA)被導入碘化鉛前驅溶液作為添加劑，以控制結晶速率和調節甲基三碘化鉛 (MAPbI3) 鈣鈦礦薄膜的薄膜形態）。這些添加劑與鈣鈦礦之間的強相互作用鈍化了缺陷，減緩了鈣鈦礦晶體的生長，並增加了晶粒尺寸。因此，在鈣鈦礦薄膜形成中使用 ClPDI 添加劑可以有效提高鈣鈦礦太陽能電池的效率和穩定性。

Global environmental and resource highly concern about the future energy demand and security will become continuously increasing depends upon the development of accessible, sustainable and scalable energy technologies. Remarkable research efforts from both academia and industry over the past decades have been dedicated in state-of-art small molecule organic with respect to polymer due to numerous advantages such as high purity and crystallinity, well-defined molecular structures, absence of end group contaminants, high mobility, and batch-to-batch reproducibility.
The most successful two-dimensional (2D)-electron donor unit, benzo[1,2-b:4,5-b´]dithiophenes (BDTs), has emerged as an fascinating building block for PSCs as well as SMOSCs owing to high-coplanarity, π-π stacking, high-mobility and enhanced solubility. Lateral flexible side chains manipulation of the electron-donating groups of BDT derivatives, that B-BDT6T substituted with ethynylthenyl, TS-BDT6T substituted with thenylthio and TT-BDT6T substituted with alkyl thienothiopehenes. The experimental results indicate that the lateral incorporation of flexible side chains without altering the end capped acceptor (cyanoacetate) moieties enable BDT-based small molecules to successfully amend the opto-electronic properties. TS-BDT6T and TT-BDT6T demonstrated good packing, in contrast to TB-BDT6T, in the solid state. Moreover, TS-BDT6T and TT-BDT6T exhibited superior charge transport properties and well-ordered separation networks distributions and, thus enhanced PCE.
The extended aromatic core in the asymmetric benzo[2,1-b:-3,4-b′:5,6-b″]trithiophene (asymmetric BTT) provided full planarity, thereby favoring intermolecular π-stacking and charge transport. The asymmetric BTT unit was used as the central core to which were appended various donor groups, carbazole (BTT-CB), thieno thiophene (BTTFT), triphenylamine (BTT-TPA), and bithiophene (BTT-TT). Good crystallinity and superior hole mobility was exhibited by BTT-TT, compared with those of the other three HTMs, and formed smooth and uniform surfaces when covering the perovskite active layer. The highest power conversion efficiency incorporating BTT-TT as the HTM was 18.58% with good stability after storage for more than 700 h.
Defects at the grain boundaries and surfaces of metal-halide perovskite films function as non-radiative recombination centers that decrease the performance and/or stability of perovskite solar cells (PSCs). Core-twisted tetrachloroperylene diimide (ClPDI) derivatives (n-type small molecules) presenting various terminal groups (n-butyl (ClPDI-C4), dimethylaminopropyl (ClPDI-OmeA), and aminopropyl (ClPDI-DPA)) were introduced into the lead iodide precursor solution as additives to control the crystallization rate and modulate the film morphology of methylammonium lead triiodide (MAPbI3) perovskite films. The strong interactions between these additives and perovskite passivated defects, slowed perovskite crystal growth, and increased the grain size. Thus, the use of ClPDI additives in perovskite film formation can effectively enhance both efficiency and stability of perovskite solar cells.

Abstract--------------------------------------------------------------------iii
摘要-------------------------------------------------------------------------v
Acknowledgment---------------------------------------------------------vii
Table of Content ----------------------------------------------------------viii
List of Figure---------------------------------------------------------------xi
List of Tables--------------------------------------------------------------xvii
CHAPTER 1: Introduction---------------------------------------------------1
1.1. Solar cell----------------------------------------------------------------1
1.2. Organic solar cells -----------------------------------------------------2
1.2.1. Basic principle of OSC -----------------------------------------------3
1.2.2. OSC device structure-------------------------------------------------5
1.2.2.1.Single polymer layer device----------------------------------------6
1.2.2.2.Bilayer polymer/acceptor structure--------------------------------6
1.2.2.3.BHJ organic solar cell structure-------------------------------------8
1.2.3.Small molecules solar cells-------------------------------------------9
1.3.Perovskite Material for Solar Cells Application-----------------------11
1.4.Solar Cells Device Characteristics-------------------------------------16
1.4.1.Short circuit current density-----------------------------------------17
1.4.2.Open circuit voltage (VOC) -----------------------------------------17
1.4.3. Fill Factor -----------------------------------------------------------17
1.4.4.Maximum power point----------------------------------------------17
1.4.5.Power conversion efficiency (PCE) ----------------------------------18
1.5.Thesis Organization---------------------------------------------------18

CHAPTER 2: Experimental Section ---------------------------------------20
2.1.Preparation of benzodithiophene-based small molecule solar cells-20
2.2.Preparation of MAPbI3 using single step method--------------------22
2.3.Preparation of ClPDI additive based perovskite solar cells-----------25
2.4.Characterization techniques------------------------------------------28

CHAPTER 3: Lateral Side Chains Engineering on Benzodithiophene-Based Small Molecules for Bulk Heterojunction Solar Cells --------------------30
3.1.Overview --------------------------------------------------------------31
3.2.Result and discussion-------------------------------------------------35
3.2.1.Optical properties---------------------------------------------------35
3.2.2.Electrochemical properties------------------------------------------37
3.2.3.Molecular order and packing ---------------------------------------39
3.2.4.Device Performance-------------------------------------------------40
3.2.5.Morphology and charge transport----------------------------------46
3.3.Summary--------------------------------------------------------------50

CHAPTER 4: Asymmetric Benzotrithiophene-Based Small Molecules for Hole Transporting Materials of Perovskite Solar Cells--------------------51
4.1.Overview--------------------------------------------------------------52
4.2.Result and discussion -------------------------------------------------56
4.2.1.Hole Transporting Material properties -----------------------------56
4.2.2.Photovoltaic performance------------------------------------------62
4.2.3.Transport properties------------------------------------------------71
4.3.Summary--------------------------------------------------------------78

CHAPTER 5: Core-Twisted Tetrachloroperylenediimides as Additives in Perovskite Solar Cells-----------------------------------------------------79
5.1.Overview--------------------------------------------------------------80
5.2.Result and Discussion-------------------------------------------------84
5.2.1.Crystallinity and Morphology of Perovskite Films------------------84
5.2.2.Photovoltaic performance------------------------------------------90
5.2.3.Photoluminescence and molecular interaction---------------------94
5.2.4.Stability of perovskite solar cells devices----------------------------99
5.3.Summary ------------------------------------------------------------102

CHAPTER 6: Conclusion and Future Perspective------------------------104
6.1.Conclusion-----------------------------------------------------------104
6.2.Future Perspective---------------------------------------------------106
References---------------------------------------------------------------108
Appendix A : Synthesis of Small Molecules -----------------------------120
Synthesis of the BDT-based small molecules TB-BDT6T, TS-BDT6T, and TT-BDT6T
Synthesis of Asymmetric Benzotrithiophene-Based BTT-CB, BTT-FT, BTT-TPA, and BTT-TT
Syntheses of the Core-Twisted Tetrachloroperylenediimide Derivatives ClPDI-C4, ClPDI- C3DMeA, and ClPDI-DPA
Appendix B : List of Publication------------------------------------------150

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