perovskite solar cell (PSCs)PSC Lecture .pptx

perovskite solar cell (PSCs)PSC Lecture .pptx

1. Perovskite Solar Cell (PSCs)

2. General Introduction

3. What is perovskite PV? ABX 3 A = (CH 3 NH 3 ) + ,(HC(NH 2 ) 2 ) + B = Pb 2+ , Sn 2+ X = Cl - , Br - , I - Typical perovskite structure ： CH 3 NH 3 PbI 3 HC(NH 2 ) 2 PbI 3 high molar extinction coefficient broad absorption spectrum tunable band gap (1.5 eV) high charge carrier mobility Preovskite is ideal for PV application: Using perovskite crystals as light absorption materials Corner-sharing octahedral structure 400 500 600 700 800 Wavelength (nm) 1 2 3 Absorbance (a.u.)

4. The first perovskite solar cell T. Miyasaka, J. Am. Chem. Soc ., 2009 , 131, 6050 4 Perovskite as dye for DSCs, η = 3.8% Nanocrystalline CH 3 NH 3 PbBr 3 on TiO 2 surface

5. Glass PT Cathode Electrolyte (iodide/triiodide) Dye TiO 2 TCO Glass D S SC Ag Cathode HTM (Spiro-OMeTAD) Dye TiO 2 TCO Glass Novel solar cell ssDSSC Perovskite PV TCO Ag Cathode HTM Perovskite TiO 2 TCO Glass Organic vs Inorganic sensitizer

6. Perovskite solar cell (PSCs) Dye sensitized solar cell (DSCs) 1991  2009  CH 3 NH 3 PbI 3 6

7. Solid State Perovskite Cell S tructure

8. Different Perovskite solar cell structures Meso-TiO 2 Planar structure Reverse structure 12

9. Perovskite Solar Cell Efficiency Progress The Best and Average Efficiency H. Zhou, et al, Science, 2014, 345, 542. N. J . Je o n , e t al., N a tu r e M a t e r . 2 1 4 , 1 3 , 897. 14 M. M. Lee, et al., Science, 2012, 338, 643. Low reproducibility Low stability Small cell area

10. Reproducibility of device Perovskite Solar Cells Research at NIMS Efficient and stable large-area PSCs Cell size: 0.09 cm 2 15

11. Our work on perovskite solar cells 16 Small Cell size: 0.09 cm 2 Device Stability Need to develop Reproducibility of device Al 2 O 3 /CH 3 NH 3 PbI 2 Cl TiO 2 /CH 3 NH 3 PbI 2 Cl

12. 17 1 . Perovskite film deposition

13. Progress of perovskite film deposition (1) One-step spin-coating a mixture of PbI 2 and CH 3 NH 3 I. η = 12.0 % (the best in meso-TiO 2 structure cells) It is difficult to control the perovskite film morphology . S. I. Seok, Nat. Photon., 2013, 7 , 486-491 The initial method 19

14. Progress of perovskite film deposition Two-step sequential deposition. η = 15.0 % (meso-TiO 2 structure) Firstly depositing PbI 2 , then dipping in CH 3 NH 3 I solution. M. Grätzel, Nature , 2013 , 499, 316-319. One-step spin-coating Two-step Improve the surface coverage! 20

15. Progress of perovskite film deposition (3) Dual-source vacuum co-evaporation. η = 15.4 % (planar structure) H. J. Snaith, Nature , 2013 , 501, 395-398. Improve the thickness uniformity! 21

16. Progress of perovskite film deposition (4) Vapor-Assisted Solution Process, VASP. η = 12.1 % (planar structure) Y . Y a n g, J. Am . Chem . Soc , 2013 , 136, 62 2 -62 5 . Two-step dipping VASP CH 3 NH 3 I vapor reacted with PbI 2 film. Improving grain size and surface roughness! 22

17. Progress of perovskite film deposition (5) Solvent engineering on one-step method. η = 16.2 % (meso-TiO 2 ） S. I. Seok, Nat. Mater ., 2014 , 13, 897-903. Toluene dripping before annealing Solution method with good surface morphology! 23

18. A summary of perovskite deposition techniques V a c uu m c o- Hi gh c ov e r a g e 120 - 32 o C > 1 h w i th c omp li c a t ed evaporation Low roughness 24 Method Film quality Temperature Time Vacuum Operation One-step spin coating Low coverage, High roughness 100-130 o C 10-40 min without simple T w o - s t ep dipping High coverage High roughness 70 o C 1-10 min without simple We want to imp rove the two step dip ping method VASP High coverage Low roughness 150 o C > 2 h without complicated Solvent engineering High coverage Low roughness 100 o C 10 min without simple High surface coverage and low roughness films are required. Simple and reproducible methods are favorable.

19. CH 3 NH 3 I Solution dipping Substr a te PbI 2 Controlling the crystallization of PbI 2 for sequential deposition CH 3 NH 3 PbI 2 Sequential deposition schedule: PbI 2 •DMF Large size PbI 2 crystals Slow and incomplete perovskite conversion from large PbI 2 crystals 25

20. Strong coordinative DMSO leads to amorphous PbI 2 film Difference between DMSO and DMF based PbI 2 films: SEM characterization of DMF and DMSO based PbI 2 films. UV-vis and XRD characterization of DMF and DMSO based PbI 2 films. No PbI 2 diffraction peaks in DMSO based film! 26 c r yst a l l i n e am o r p h o u s Layered packed PbI 2 crystals not formed in DMSO based film Amorphous PbI 2 films has smooth surface because of strongly coordinative DMSO

21. Coordination between PbI 2 and solvents Coordination ratio, 1:1 Pb-O bond length: 2.431 Å PbI 2 •DMF PbI 2 •(DMSO) 2 DMF I Pb A. Wakamiya, et al., Chem. Lett., 2014, 43 , 711-713. H. Miyamae, et al., Chem. Lett ., 1980, 9 , 663-664. DMSO has stronger coordination capability with PbI 2 in comparison to DMF. Coordination ratio, 1:2 Pb-O bond length: 2.386 Å D M SO Pb I

22. Control the crystallization of perovskite films PbI 2 -DMSO complexes control the reaction kinetics between PbI 2 and CH 3 NH 3 I; The Pb 2+ in the amorphous film has almost equal probability to react with CH 3 NH 3 I; Complete conversion on planar substrate is much easier for amorphous PbI 2 . (a) evolution of absorbance at 750 nm upon dipping time of the PbI 2 films in CH 3 NH 3 I solutions. (b) XRD patterns of the films obtained by dipping DMF and DMFO based PbI 2 films in CH 3 NH 3 I solutions for 10 min, * are signals come from substrate. Complete conversion! Incomplete conversion! Slow conversion of inner PbI 2 , Conversion finished within 10 min. Amorphous PbI 2 show fast and complete conversion into perovskite film via sequential deposition Energy Environ. Sci ., 2014, 7, 2934

23. Particle size statistics Crystalline PbI 2 produced perovskite particles are broadly distributed from 50 to 330 nm. Amorphous PbI 2 produced perovskite has a smaller distribution of particle size, with more than 80% located in a small range around 200 ± 20 nm T op vie w of the film Broad distribution! Uniform distribution! Uniform perovskite film was obtained from amorphous PbI 2 29 Uniform perovskite film generated from amorphous PbI 2

24. Reproducible planar-structured perovskite solar cells The amorphous PbI2 based perovskite films enabled reproducible planar-structured perovskite solar cells with the best efficiency of 13.5%, average efficiency of 12.5% and a small standard deviation of 0.57 from 120 specimens. Amorphous PbI 2 Crystalline PbI 2 The highest efficiency 13.5% 14.2% The lowest efficiency 10.8% 1.3% The average efficiency 12.5% 9.7% The standard deviation 0.57 2.47 Table 1 Statistics of device performance in group A and B. a The data were analyzed from totally 120 cells for each group. Jsc[mA/mc 2 ] Voc[V] F.F. Eff[%] 20.71 1.02 0.64 13.5 L . Y . Ha n, e t al., E n er g y E n vi ron . S ci., DOI: 10.1039/C4EE01624F (2014) A m o r pho u s Pb I 2 Crystalline PbI 2 Planar structure, High efficiency! High reproducibility! The device reproducibility was improved by controlling the perovskite morphology

25. The strategy of using coordinative DMSO-PbI 2 complexes for FAPbI 3 perovskite lead to high PCE over 20% S. I. Seok, et al., Science , 2015, 348 , 1234-1237 Jsc: 24.7 mA cm -2 Voc: 1.06 V FF: 0.775 31 PCE: 20.2% (0.096 cm 2 ) DMSO-PbI 2 Normal PbI 2 Optimization of the coordinative DMSO-PbI 2 complexes

26. 32 2. Reverse structure: Efficient and stable large-area PSCs

27. 33 Normal structure Reverse structure Two Typical Structures of Perovskite Solar Cells L i ght L i ght Reverse structure PSCs Inorganic HTM like NiO can have better stability than organic HTM However its efficiency is relatively low

28. 34 Problem of Inorganic HTM SEM of Perovskite film on different HTM layers Thin NiO Caves in perovskite film may reduce the device performance

29. Inverted perovskite solar cells based on NiO/meso-Al 2 O 3 Hybrid interfacial layer of compact NiO/meso-Al 2 O 3 , with minimal light absorption and interfacial recombination losses. 35 (20 nm) (50 nm) N i O TiO 2 Al 2 O 3

30. Top view on NiO/meso-Al 2 O 3 FTO Thin NiO Thick NiO Meso-Al2O3 Meso-Al2O3: 80 nm Thin NiO: 20 nm Thick NiO: 50 nm (a-d) SEM images; (e-f) TEM images NiO films made by spray pyrolysis Energy Environ. Sci., 2014 , DOI: 10.1039/C4EE02833C 36

31. Device performance Jsc V oc FF Efficiency NiO/meso-Al 2 O 3 hybrid interlayer shows better Fill Factor and higher Voc because it can suppress the formation of caves in perovskite film. 37 Efficiency increased to > 13%

32. 38 Robust inorganic nature Heavily doped inorganic charge extraction layers Fig. (A) Scheme of the cell configuration; composition of Ti(Nb)Ox and the crystal structure of NiMg(Li)O. (B) SEM image of a complete solar. (C) Band alignments of the solar cell. Inverted PSCs based on robust charge extraction layers

33. J-V curves of solar cells based on different combinations of charge extraction layers with standard thickness (NiO, NiMg(Li)O = 20 nm; TiOx, Ti(Nb)Ox = 10 nm). Doping enhanced photovoltaic performance 39

34. Normalized PL transient decay curves of perovskite Perovskite and perovskite at the controlled interfaces of NiO and NiMg(Li)O 40 PL decays to 1/e of the initial intensity is defined as the characteristic lifetime (τ) of free carriers after photoexcitation. Doping has a negligible influence on the hole injection

35. Transient photocurrent and photo-voltage decay curves The charge transport (τ t ) and recombination time (τ r ) are defined as the time interval during which the photocurrent or photovoltage decays to 1/e of the their initial value immediately after excitation. 41 Undoped and doped charge carrier extraction layers The doping-induced difference in charge transport/ recombination kinetics should be the main reason responsible for their performance enhancement

36. Certified large size (1 cm 2 ) perovskite solar cell >90% of the initial PCE remained after 1000 hours light soaking Efficient and stable large-area perovskite solar cells 42

37. 43 3. Graded perovskite-fullerene heterojunction

38. Graded perovskite-fullerene heterojunction (GHJ) Pe r o vsk it e : F A 0.8 5 M A 0. 1 5 Pb(I 0.8 5 B r . 1 5 ) 3 PCBM: phenyl–C 61 –butyric acid methyl ester HEL: Ni ( Mg L i )O EEL: T i(N b )Ox Ano d e : F T O gl a ss C a th od e : Ag 44 The inverted-structured perovskite solar cells have shown less hysteresis and high stability. However, their efficiency is lagged behind the normal- structure. Electron-transporting characters of perovskite layer and EEL play important roles on affecting the photovoltaic performance of inverted PSCs. We report an inverted device architecture with a graded heterojunction (GHJ) structure

39. Perovskite/PCBM GHJ film fabricated by the fullerene solution dripping deposition SEM image of the dripping-induced perovskite–PCBM XRD patterns of perovskite films with PCBM without PCBM The disappearance of the grain texture was caused by the coating of PCBM through the dripping solvent deposition XRD patterns indicate the crystal structure is the same for the perovskite films fabricated without or with PCBM. Top-view SEM: 45 perovskite/PCBM GHJ pristine perovskite

40. Graded perovskite-fullerene heterojunction Time-resolved PL spectra of perovskite film Sample of perovskite-PCBM PHJ (Planar heterojunction) quenches PL   only by 81%, while GHJ sample quenches PL >95% Transient PL measurements showed faster decay of GHJ sample The increased PL quenching yield of the GHJ sample indicates an improved electron transfer from perovskite to fullerene of the GHJ. PH J GHJ PL spectra of perovskite film No PCBM 46

41. Device performance of FA-MA based GHJ solar cell The GHJ greatly enhanced the pe r forma n ce of F A -MA mi x ed c a tion based perovskite in inverted- structured PSCs. A PCE of 18.21% was obtained with cell area of 1.022 cm 2 Eff. = 18.21% Area = 1.022 cm 2 GHJ PH J GHJ Nature Energy, Vol 1, November 2016 47 PH J J – V curves and IPCE spectra

42. Hysteresis, reproducibility and stability of GHJ devices 48

43. Graded heterojunction Fabrication and characterization of perovskite–fullerene GHJ 49

44. 1 5 Diffusion engineering of ions and charge carriers: stable PSCs E. Bi, A. Islam, M. Gratzel, L. Han, et al.; NATURE COMMUNICATIONS June 2017, Hinder unfavourable iodide/water molecules diffusion Accelerate photo generated charges diffusion SEM cross-section FTO/ NiMgLiO/Perovskite/G-PCBM/CQDs/Ag G-PCBM: PCBM doped with 2 wt% N-doped graphene to block the layer-to-layer diffusion of iodide or water molecules CQDs: carbon quantum dots Diffusion processes within nanocarbon-based EEL Energy band structure

45. FTO/NiMgLiO (20 nm)/MAPbI 3 (350 nm)/G-PCBM (150 nm)/CQDs (10 nm)/Ag I-V and IPCE characteristics Stability of sealed devices under dark and under air AM 1.5G Stability of sealed cells in thermal ageing test at 85 ºC in 50% humidity 51 PCE 17.0% small hysteresis J SC matched well with I-V The stable efficient PSCs (over 15%) during long-term thermal ageing and light soaking test Indicates nanocarbon layer (G-PCBM/CQDs) plays the key role in the device stability

46. Electron extraction and charge recombination TRPL decay curves A faster charge extraction observed in G-PCBM steady-state PL Transient photocurrent decay Transient photovoltage decay 52 A strong quenching of PL was observed for the perovskite/G-PCBM film; indicate faster electron transport CQDs/G-PCBM based devices exhibited a much more rapid photocurrent decay, confirming the faster electron transport The CQDs/G-PCBM device with a V OC of 1.09V exhibited slower photovoltage decay (109.45  s), indicating a better retardation of carrier recombination

47. Summary The amorphous PbI 2 based perovskite films enabled reproducible planar-structured perovskite solar cells with the best efficiency of 13.5% Developed a hybrid interfacial layer of “compact NiO/meso-Al 2 O 3 ” for inverted PSC, which leads to a high efficiency of > 13% A record efficiency of 15% in the large size (1 cm 2 ) perovskite solar cell (PSC) obtained using a robust charge extraction layers: >90% of the initial PCE remained after 1000 h light soaking Graded perovskite-fulllerene heterojunction (GHJ) structure can greatly improve the performance of inverted-structured PSCs. A PCE of 19.2% was obtained with cell area of 1.022 cm 2 Issues to be addressed Toxicity of Pb : CH 3 NH 3 Pb X 3  Led free Long term stability at critical environment condition 53

48. Thank you for your kind attention