Title Page
Contents
Abstract 17
Chapter 1. Introduction 19
1.1. Climate change, Net zero and Solar Energy 19
1.2. Perovskite Solar Cells 21
1.3. Metal oxide charge transporting layer for PSCs 23
1.4. PSCs and Atomic Layer Deposition 25
1.4.1. Basic principles of ALD 26
1.4.2. Advantages of atomic layer deposition 28
1.4.3. Charge transporting layer with ALD 31
1.5. Motivation 32
Chapter 2. Hole Transporting Vanadium-containing Oxide(V₂O₅-ₓ) Interlayers Protect α-FAPbI₃-based Perovskite Solar Cells (~ 23%) 34
2.1. Abstract 34
2.2. Introduction 35
2.3. Hole transporting properties of ALD-V₂O₅-ₓ 39
2.4. Stability of perovskite films with ALD-V₂O₅-ₓ 43
2.5. Conclusion 48
Chapter 3. Practical and thermal ALD of NiO with different oxidant for HTL 52
3.1. Abstract 52
3.2. Introduction 52
3.3. Structural and Optical properties of h-NiO and o-NiO 58
3.4. XPS analysis of h-NiO and o-NiO 63
3.5. Effect of oxidation power of oxidant during ALD-NiO process for i-PSCs 67
3.6. Conclusions 72
Chapter 4. Dual Strategies with Defect Suppression and Hole Transporting Bilayer for Inverted Perovskite Solar Cell (PCE ~24%) 76
4.1. Abstract 76
4.2. Introduction 77
4.3. Perovskite composition and additive engineering 82
4.4. Formation of bi-layer HTL with ALD-NiO 90
4.5. Conclusion 105
Summary and Conclusion 111
References 113
Appendix 1. Permission to copyright 130
국문초록 131
Table 3.1. Summarized representing works about i-PSCs utilizing NiO as HTL. To prevent misunderstandings, we directly transcribed the abbreviations and other notations used in the each paper.... 57
Table 3.2. Reported ALD-NiO processes with different Ni precursors and Oxidants. 58
Table 3.3. Atomic ratio analysis of fabricated films conducted by XPS Analysis (ESCA LABII). Through post-annealing process (300℃ at box furnace), residual nitrogen from MABON ligands were annihilated. 59
Table 3.4. Fitted parameter of Time resolved Photoluminescence (TRPL) spectrums at Figure S5. Biexponential decay function: y＝y₀ + A₁e-x/t¹ + A₂e-x/t² was adopted.[이미지참조] 62
Table 3.5. Reported i-PSCs with only ALD based NiO as HTL. Our group : Thermal ALD with O₃ or H₂O₂ Group ▲ : Plasma assist ALD Group ● : atmostpheric spatial ALD[이미지참조] 72
Table 4.1. Fitted parameter of Time resolved Photoluminescence (TRPL) spectrums at Figure 4.3. 85
Table 4.2. Fitted parameter of Time resolved Photoluminescence (TRPL) spectrums at Figure 4.19 100
Table 4.3. Summary of substrate, HTL, PCE and JSC of representative i-PSCs report.[이미지참조] 104
Table 4.4. Photovoltaic parameters of fabricates i-PSCs based on sol-gel NiO and sol-gel NiO/Me-4PACz as HTL. 104
Figure 1.1. U.S. planned utility-scale electric-generating capacity in 2023. 19
Figure 1.2. The prospective market scale of the global solar industry. (TRPV 2022, 13. Edition, March 2022) 20
Figure 1.3. Best Research-Cell Efficiency Chart certified by NREL. (data access: Nov.2023) 21
Figure 1.4. (a) Perovskite structure with ABX₃ and [BX₆]⁴⁻ octahedral cage. (b) Tolerance factor and octahedral factor of perovskite with different A-site and X-site. 22
Figure 1.5. Types of PSCs. n-i-p normal structure n-PSCs, mesostructured n-PSCs and p-i-n inverted structure i-PSCs. 24
Figure 1.6. Periodic table and overview of materials deposited by ALD. 26
Figure 1.7. Schematic of basic Atomic Layer Deposition (ALD) system 27
Figure 1.8. The ALD deposition cycle composed with sequence of steps: a metal precursor pulse-purge with inert gas, followed by an oxidant pulse-purge with inert gas. 28
Figure 1.9. ALD window with different deposition temperature. 30
Figure 1.10. Homemade large scale ALD chamber and thickness mapping of deposited ALD-SnO₂ on Si wafer. The thickness mapping result is carried out with spectroscopic ellipsometry. 31
Figure 2.1. Estimated growth rate (0.4Å/cycs) by XRR depends on the number of cycles. (Equipment and fitting program is Rigaku SmartLAB and GlobalFit respectively) 40
Figure 2.2. XRD analysis without(black) and with(green) ALD-V₂O₅-ₓ deposited onto Spi. (# - PbI₂, α - FAPbI₃, ● - FTO (internal reference)) (b) XRD patterns of V₂O₅-ₓ films on SiO₂ wafer. After annealing at...[이미지참조] 41
Figure 2.3. (a)UV-Vis absorption spectra for perovskite/Spiro-OMeTAD without (black curve) and with (green) V₂O₅-ₓ films, respectively, and (b) estimated optical band gap of 1.55 eV following Tauc plot with... 41
Figure 2.4. Steady-state photoluminescence (SSPL) spectrums of the perovskite/Spi layer with (green line)/without (red line) the V₂O₅-ₓ layer. 42
Figure 2.5. Measured XPS spectrums of (a) as-deposited and (b) post-annealing (400℃, 1h) ALD-V₂O₅-ₓ films (~4 nm, 100 cycles of ALD) on FTO. The fitted curves correspond to V⁵⁺ state, V⁵⁺ and integrated are... 43
Figure 2.6. Normalized absorbance at 600nm of Perovskite/Spi and Perovskite/Spi/V₂O₅-ₓ. Absorbance of Perovskite/Spi decrease less than 70%, while Perovskite/Spi/V₂O₅-ₓ maintained. 45
Figure 2.7. XRD patterns of perovskite/spi films without and with V₂O₅-ₓ stored under high humidity condition (RH~80± 5%) for 30hour 46
Figure 2.8. (a) XRD patterns of perovskite films without or with ALD-V₂O₅-ₓ. Morphological change in SEM images of films for (b) perovskite/Spi and (c) perovskite/Spi/V₂O₅-... 46
Figure 2.9. (a) Schematic illustration of fabricated PSCs with ALD V₂O₅-ₓ and (b) Best performing PSCs without and with different number of cycles of ALD-V₂O₅-ₓ 47
Figure 2.10. Statistical photovoltaic parameters of a) power conversion efficiency (%), b) short-circuit current density (J SC ; mA/cm²), c) open-circuit voltage (VOC ; V), and e) FF.[이미지참조] 47
Figure 3.1. (a) GIXRD patterns of ALD-NiO films deposited with H₂O₂ as an oxidant (h-NiO). The peak corresponding to JCPDS was consistent with a cubic rock-salt crystal structure of NiO, as shown... 59
Figure 3.2. GIXRD patterns of h-NiO, o-NiO and s-NiO on Si wafer and JCPDS (00-047-1049). All films are after annealing state. The thickness of h-NiO and o-NiO is around 7.0 nm and s-NiO is around 25.0 nm.... 60
Figure 3.3. UV-Vis spectroscopy of as-deposited(as-dep) and post-annealing NiO films with the optimized thickness of ~7nm on FTO substrate (a), corresponding tauc plot indicating the electronic band gap of ~... 61
Figure 3.4. (a) Steady State Photoluminescence (ssPL) and (b) Time resolved Photoluminescence (TRPL) spectrums of FTO/Perovskite, FTO/h-NiO/Perovskite, FTO/o-NiO/Perovskite. The thickness of both... 62
Figure 3.5. XPS results of the (a, d) as-deposited h-NiO, (b, e) annealed h-NiO, and (c, f) annealed o-NiO films. Ni 2p spectra of (a) as-deposited h-NiO, (b) annealed h-NiO, and (c) annealed o-NiO films.... 63
Figure 3.6. X-ray Photoelectron Spectroscopy (XPS) of the (a, c) as-deposited o-NiO; (b, d) annealed sol-gel NiO. Ni 2p spectrums of (a) o-NiO as-deposited (b) annealed s-NiO respectively. High-resolution (a,... 64
Figure 3.7. Ultra-violet Photoelectron Spectroscopy (UPS) spectrum of o-NiO and h-NiO films on Si wafer. a) full spectrum b) and c) cutoff spectrum. Work function is calculated by WF＝21.22eV -(Ecutoff-...[이미지참조] 67
Figure 3.8. Photovoltaic properties dependance statistics about thickness of h-NiO. a) Power conversion efficiency (%) b) Open circuit voltage (VOC; V) c) Short-circuit current density (JSC; mA/cm²) d) FF.[이미지참조] 68
Figure 3.9. Plotted photovoltaic parameters of each perovskite solar cells based on 3 types of NiO. The thickness of both h-NiO and o-NiO was ~ 7.0 nm and s-NiO 20~30 nm. a) Power conversion efficiency... 69
Figure 3.10. The I-V characteristic comparison of h-NiO and o-NiO at asdep and post-annealing state. The device configuration is Si/h-NiO or o-NiO/Au. The thickness of ALD-NiO is 8nm and Au electrode radius... 69
Figure 3.11. Scanning electron microscopy (SEM) image of the fabricated device and perovskite layer on top of the FTO/h-NiO or o-NiO substrate. (a) and (b) show cross-sectional images of FTO/h-... 70
Figure 3.12. (a) J-V curves of the best-performing i-PSC and statistical photovoltaic parameters of b) power conversion efficiency (%), c) open-circuit voltage (VOC; V), d) short-circuit current density (JSC;...[이미지참조] 71
Figure 4.1. Device performance of fabricated i-PSCs with ALD-NiO depending on concentration of MAPbBr₃. (a) Power conversion efficiency (%) (b) Short-circuit current density (JSC; mA/cm²) (c) Open... 82
Figure 4.2. Steady state Photoluminescence (ssPL) spectrums of perovskite with different concentration of MAPbBr₃. The peak position of FAPbI₃, X＝2.5%, X＝5%, X＝7.5% and X＝15%... 83
Figure 4.3. (a) Spin coating process with and without PyBF₄ as additive and molecular structure of Py BF₄ (b)-(e) Statistical analysis of i-PSCs with different concentration of x-... 84
Figure 4.4. (a) Steady state Photoluminescence (ssPL) spectrums and (b) time-resolved Photoluminescence (TRPL) of reference and 0. 25 % of PyBF₄ PSCs. The TRPL data was... 85
Figure 4.5. FESEM image of fabricated i-PSCs with (a, b) reference, and (c, d) perovskite with 0.25mol% PyBF₄ (a,c) show cross sectional image of fabricated i-PSCs and (b, d) are morphological... 86
Figure 4.6. X-ray diffraction (XRD) patters of reference and perovskite with 0.25mol% of PyBF₄. The ● peak is SnO₂ from FTO as internal references. No significant change was observed...[이미지참조] 87
Figure 4.7. Device structure of TAS analysis and (b) C vs. V curve and extracted Mott-Schottky plot 88
Figure 4.8. Thermal admittance spectroscopy (TAS) of reference or with 0.25mol% PyBF₄ perovskite layer. (a,b) capacitance vs. frequency curve (c, d) first derivative of capacitance with respect to frequency (e)... 89
Figure 4.9. Cross-sectional Transmission Electron Microscopy (TEM) image of ALD-NiO (10nm) on FTO. (a) Mosaic images with low magnification (see, scale bar is 200 nm in length). The ALD NiO showed an... 91
Figure 4.10. FESEM images of perovskite deposited on each substrate (a) FTO (b) FTO/ALD-NiO (c) FTO/ALD-NiO/Me-4PACz (d)FTO/Me-4PACz. The inset is grain size histogram of 100 perovskite grains... 92
Figure 4.11. Contact angle measurement with each film with water droplet. The contact angle was measured after 1 min of drop. 92
Figure 4.12. FESEM image and EDS mapping conducted with FESEM. Perovskite with 0.25mol% PyBF₄ deposited on (a-c) FTO/ALD-NiO (d-f) FTO/ALD-NiO/Me-4PACz (g-i) FTO/Me-4PACz 93
Figure 4.13. (a,b) Cross-sectional TEM images of FTO/ALD-NiO/Me-4PACz and FTO/Me-4PACz and inset shows EDS signal from P(cyan), Sn(green) and Ni(Pink) (c,d) TEM EDS mapping of yellow box and... 94
Figure 4.14. (a) Ni 2p spectrums of ALD-NiO with main lattice (Peak A), nonlocal screening peak (Peak B) and satellites (Peak C and Peak D). (b) Ni 2p spectrums without or with Me-4PACz. The binding energy... 95
Figure 4.15. (a) Histogram summarizes 300 points of contact potential difference. The tip is calibrated by HOPG. (b) Schematic diagram of ALD-NiO or ALD-NiO/Me-4PACz. Each layer deposited on FTO. 97
Figure 4.16. (a) Ambient pressure photoemission spectroscopy (APS) of each HTL and (b) UV-Vis spectroscopy of ALD-NiO and (c) corresponding tauc plot. The optical band gap was... 97
Figure 4.17. Ultra-violet photoemission spectroscopy of ALD-NiO (a,b) and perovskite with 0.25mol% PyBF₄(c,d). Workfunction (WF) calculated with extracting cut-off values from He (I)... 98
Figure 4.18. (a) Band structure of reference and with 0.25mol% PyBF₄ calculated with (b) KP and (c) corresponding APS (d) UV-Vis spectroscopy and (e) corresponding tauc plot. The optical band... 99
Figure 4.19. (a) ssPL spectra and (b) Decay curves of perovskite with 0.25mol% of PyBF₄ on each HTL. The TRPL data was fitted with biexponential decay function and detailed fitting parameters... 99
Figure 4.20. Photovoltaic properties dependance statistics about ALD-NiO, standalone Me-4PACz and ALD-NiO/Me-4PACz. (a) Power conversion efficiency (%) (b) Short-circuit current density... 101
Figure 4.21. (a) J-V curves of i-PSCs with ALD-NiO/Me-4PACz bi-layer HTL and (b) corresponding external quantum efficiency spectra with current density integrated from incident photon-to-current... 101
Figure 4.22. A plot of JSC vs. PCE of representative i-PSCs in Table S3. Most of reports using ITO substrates and organic HTL.[이미지참조] 102
Figure 4.23. J-V curves of i-PSCs with ALD-NiO(black), standalone Me-4PACz(blue) and ALD-NiO/Me-4PACz bi-layer(green) as HTL. 103