Metal Halide Perovskites: a New Family of Semiconductors for Photovoltaics and Optoelectronics

Transcription

1 Metal Halide Perovskites: a New Family of Semiconductors for Photovoltaics and Optoelectronics Henry J. Snaith Department of Physics Clarendon Laboratory Parks Road Oxford OX1 3PU henry.snaith@physics.ox.ac.uk james.ball@physics.ox.ac.uk Photovoltaics and Optoelectronic Devices Group

2 Perovskites Perovskite is a calcium titanium oxide, with the chemical formula CaTiO 3. The mineral was discovered in the Ural Mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist Count Lev Alekseevich Perovski ( ). All materials with the same crystal structure as CaTiO 3, namely ABX 3, are termed perovskites.

3 1892: 1 st paper on lead halide perovskites Structure deduced 1959: Kongelige Danske Videnskabernes Selskab, Matematisk-Fysike Meddelelser (1959) 32, p1-p17 Author: Moller, C.K. Title: The structure of cesium plumbo iodide Cs Pb I 3

4 First Solar Cells

5 Perovskite solar cells Meso-Al 2 O 3 η =10.9% Meso-TiO 2 η =7.6% Planar Junction η =1.8%

6 Efficient Planar Heterojunction Solar Cells M. Liu et al. Nature 2013

7 Publications on perovskites Perovskite solar cells High T c Superconductors

8 Publications Vs Efficiency Perovskite Solar Cells

9 Crystallisation of Perovskite Thin Films

10 W. Zhang et al Nature Communications Crystallisation of perovskite thin films PbX CH 3 NH 3 I CH 3 NH 3 PbI CH 3 NH 3 X (X= Cl, I, Ac)

11 XRD The more volatile the MAX component, the faster crystallisation occurs

12 Anti-solvent quenching crystallisation (a) (b) (c) (d) Routes developed by Seok et al. and Spiccia et al.

13 Anti-solvent + Excess organic

14 Excess organic + excess PbI 2 3MAI:(PbCl (2-2x) PbI (2x) ) 3MAI:PbCl 2 2% PbI 2 5% PbI 2 40% PbI 2 100% PbI 2 N. Saki et al. Small 2017 (in-press)

15 Excess organic + excess PbI 2 3MAI:PbCl 2 2% PbI 2 5% PbI 2 30% PbI 2 100% PbI 2

16 Control over nucleation and growth 19.1% Efficiency Formulation 1 Formulation 2 Formulation 3 Formulation 1 Formulation 2 Formulation 3 Formulation 1 Jsc Formulation 1 SPO Formulation 2 Jsc Formulation 2 SPO Formulation 3 Jsc Formulation 3 SPO

17 What are the cation options? G. Eperon et al Goldshmidt Tolerance factor

18 Adding a small amount of Cs to FAPb(I 1-x Br x ) 3 Ability to crystallise throughout the entire I-Br compositional range

19 Influence of Colloids In solution

20 Influence of Addition of Acid (HI and HBr)

21 Increased crystallinity and crystal orientation

22 Microstrain and Charge Carrier Mobility

23 Crystallinity Matters D. McMeekin et al Submitted

24 A new route for single crystal Growth

25 Breaking up of colloids

26 Breaking up of colloids

27 What we think about the mechanism

28 Solvent Mixtures Solvent needs to be polar and aprotic. H 2 O/MA EtOH/MA ACN ACN/MA

29 N. Noel et al. EES 2016 In-press

30 Devices from ACN/MA solvent mix annealed unannealed inverted N. Noel et al. EES 2016 In-press

31 Enhanced Stability Perovskite Solar Cells

32 Thermal stability good B Absorption (a.u.) MAPb(I 0.6 Br 0.4 ) 3 t = 0h t = 1h t = 2h t = 3h t = 4h t = 6h 5 C FA 0.83 Cs 0.17 Pb(I 0.6 Br 0.4 ) 3 Absorption (a.u.) t = 0h t = 1h t = 2h t = 3h t = 4h t = 6h Wavelength (nm) D. McMeekin et al. Science Wavelength (nm)

33 Champion Devices C 60 derivative 1.6eV gap PCBM n-type PCBCB n-type

34 Inverted Cell Architecture Ag/Au ZnO nanocrystal PCBM FA 0.85 Cs 0.15 Pb(I 0.9 Br 0.1 ) 3 SPO: 18.2% FA(MA)CsPb(I 0.9 Br 0.1 ) 3 NiO ITO Substrates FA 0.79 MA 0.16 Cs 0.05 Pb(I 0.9 Br 0.1 ) 3 SPO: 19.3% J SC (ma cm -2 ) V OC (V) FF PCE (%) FB-SC SC-FB J SC (ma cm -2 ) V OC (V) FF PCE (%) FB-SC SC-FB S. Bai et al. (In preparation) 2017

35 Non-encapsulated solar cells Burn-in t 80 = 1050 h t 80 = 694 h t 80 = 20.7 h The devices are aged under full spectrum simulated AM1.5, 76 mwcm -2 average irradiance at V OC in air without a UV filter, 53 C. The Suntest XLS+ aging box irradiates pulsed light.

36 Sealed vs unsealed

37

38 But

39 And cheaper

40 Best Way to Raise Efficiency Epitaxially Grown Single Crystal III-V Tandem 46% efficient >$40,000/m 2 Perovskite on Conventional Silicon Tandem Up to 33% efficient <$100/m 2 Image: US Naval Research Lab

41 Perovskite on Si Eg. See papers by Baliff et al and McGehee et al,

42 Simple 4-T configuration Glass FTO SnO 2 /PCBM Perovskite Spiro-OMeTAD Buffer layer ITO ITO (80 nm) (p)a-si:h (~10nm) + Ai - (i)a-si:h (<10nm) Demonstrates Feasibility for > 25% efficiency D. McMeekin et al. Science 2016 DOI /science.aad5845 (n)c-si (~200µm) (i)a-si:h (<10nm) (n + )a-si:h (~30nm) Al

43 EQE and 1-R (%) Perovskite-on-Si Tandem EQE and 1-R Wavelength (nm) EQE Sum IR HIT2 - Perovskite EQE mA IR HIT2 - Silicon EQE mA IR HIT 2-1-R In collaboration with m. McGehee et al. in Stanford University

44 23.6%-Efficient Monolithic Perovskite/Silicon Tandem Solar Cells with Improved Stability Kevin A. Bush 1, Axel F. Palmstrom 1, Zhengshan J. Yu 2, Mathieu Boccard 2, Rongrong Cheacharoen 1, Jonathan P. Mailoa 3, David P. McMeekin 4, Robert L. Z. Hoye 3, Colin D. Bailie 1, Tomas Leijtens 1, Ian Marius Peters 3, Maxmillian C. Minichetti 1, Nicholas Rolston 1, Rohit Prasanna 1, Sarah Sofia 3, Duncan Harwood 5, Wen Ma 6, Farhad Moghadam 6, Henry J. Snaith 4, Tonio Buonassisi 3, Zachary C. Holman* 2, Stacey F. Bent 1, and Michael D. McGehee* 1 1 Stanford University, Stanford, 94305, USA. 2 Arizona State University, Tempe, 85281, USA. 3 Massachusetts Institute of Technology, Cambridge, 02139, USA. 4 University of Oxford, Oxford, UK. 5 D2 Solar LLC, San Jose, 95131, USA. 6 SunPreme, Sunnyvale, 94085, USA.

45 Can we go to All-Perovskite tandem We need a low band gap perovskite cell

46 1.2eV planar devices? Noel et al, EES :1 MAI:SnI2 in DMF? not so promising morphology. Tin-based materials seem to crystallise very rapidly, during spin-coating

47 Precursor-phase Antisolvent Immersion for high quality films 1. After spin-coating 2. After immersion in anisole bath 4. After annealing. 50um 10um 2um

48 FAPb 1-x Sn x I 3 : Photoluminescence PL counts (norm) Sn percentage 0% 12.5% 25% 37.5% 50% 62.5% 75% 87.5% 100% Wavelength (nm) Bandgap (ev) Eg from absorption(tauc) (ev) PL peak (BP measured - new samples) (ev) % 12.5% 25% 37.5% 50% 62.5% 75% 87.5% 100% Sn %

49 Cs addition enables a very high V OC for a 1.2 ev band gap material G. Eperon et al. Science 2016

50 All perovskite tandems G. Eperon et al. Science 2016

51 Sn-Pb devices show unprecedented stability

52 Is it worth going tandem without the low gap perovskites? Calculated EQE and JVs assuming KRICT record cell parameters A 22.1% APbX 3 single junction becomes a 25.9% APbX 3 /APbX 3 tandem Target: cell with a band gap of 2.06eV and V oc of 1.59V On Silicon, a 30.1% hybrid-tandem becomes a 33.6% triple junction (+ 0.7V Voc due to Si rear, and FF boost to 0.85)

53 Beyond Group XIV elements: G. Volonakis et al. JPCL 2016 ALSO See: Slavney, A. H et al. JACS 2016 McClure, E. T. et al. Chem. Matter. 2016

54 Calculated Band-gaps and effective mass

55 Single Crystal Data G. Volonakis et al. JPCL 2016

56 Commercialisation Device and mini-module development Present Target: Develop stable and efficient materials stack Develop processing methodology to deliver Efficient perovskite/silicon tandem cells at high yield Partner with existing Si-PV industry to manufacture

57 Test and reliability laboratory Requirements: Climatic testing to IEC C/85% RH >1000hrs +85 to -40 C cycling >200 cycles Full Spectrum Light soaking to AM1.5G 3000hrs (not IEC) High UV exposure Etc etc etc

58 IEC Stability testing 85 C for 1000 s of hrs 85 C 85% RH for 1000 s hrs High levels of UV light exposure Thermal Cycling from -40 to +85 C Full sun light exposure at 60 to 85C Important note: IEC = 1000hrs 25 years = 218,850 hrs

59 Proper Encapsulation of Cells Normalised perovskite Colour Intensity (%) Encapsulation selection using 1000hr 85 o C/85% baseline Moisture ingress accelerates degradation Control (140) Control (115) A B C Module 0 Glass Stressing Time (hours) Cover Glass Interlayer Perovskite Film 0 hrs Interlayer assembly only 350hrs Perovskite layer degradation by moisture ingress after early lamination failure

60 Stability: IEC61646 Results Thermal Cycling: Pass Full sun light soaking: Pass Damp heat: Pass

61 Next Steps: Development Through to Manufacturing

62 Oxford PV acquires thin-film development line for perovskite scale-up It has acquired the production site previously operated by Bosch Solar CISTech GmbH. The site, located in Brandenburg an der Havel, Germany, will be equipped to provide modern, pilot-scale capacity to scale-up Oxford PV s perovskite technology to industry-standard wafer size and to perfect the manufacturing processes necessary for commercial deployment.

63 qv hν qv operation(=mp) [ev] Evolution of Operational loss in perovskite cells 1.2 SQ- Limit Loss c-si GaAs CdTe 22.1% 9.7% a-si 14.1% 10.9% 17.9% 20.1% GaInP 0.2 S-Q from R.Milo,WIS Nayak et al. Adv. Mater., ,3-2014; updated Absorption Edge (ev)

64 Why are metal halide perovskites such good solar cell materials???

65 Sharp and strong absorption edge Urbach energy as low as 13 mev Steepness of absorption edge depicts quality of semiconductor Steeper = lower disorder = higher voltage Technology Urbach Energy (mev) GaAs 7 c-si 11 Perovskite 15 Christoph Baliff and co workers JPCL (6), pp CIGS 25 Organics 25-50

66 Electroluminescence vs Absorption onset.

67 PLQE and lasing!! Very High Photo Luminescent quantum yield Negligible nonradiative decay PLQE (%) Excitation power (mw/cm²) Counts (x10 6 ) Fluence ( J/cm 2 ) (scaled x25) PL Spectrum Wavelength (nm) Even room temperature lasing of as cast films within a cavity Felix Deschler et al. JPCL 2014

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69 Acknowledgements Group Research group Collaborators: Oxford: Laura Herz, Michael Johnston, Robin Nicholas, Moritz Reide Cambridge: Richard Friend and co-workers Stanford: M. McGehee et al. GT: Seth Marder et al. Bordeaux: Guillaume Wantz et al. Funding EPSRC, ERC & FP7, Oxford John Fell Fund, Oxford Martin School, Royal Society.