Metal Halide Perovskites: a New Family of Semiconductors for - PowerPoint PPT Presentation

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 Photovoltaics and henry.snaith@physics.ox.ac.uk e-mail: james.ball@physics.ox.ac.uk Optoelectronic Devices Group

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 (1792 –1856).” All materials with the same crystal structure as CaTiO 3 , namely ABX 3 , are termed perovskites.

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

First Solar Cells

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

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

Publications on perovskites Perovskite solar cells High T c Superconductors

Publications Vs Efficiency Perovskite Solar Cells

Crystallisation of Perovskite Thin Films

Crystallisation of perovskite thin films PbX 2 + 3 CH 3 NH 3 I CH 3 NH 3 PbI 3 + 2 CH 3 NH 3 X (X= Cl, I, Ac) W. Zhang et al. 2014 Nature Communications

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

“Anti - solvent” quenching crystallisation (a) (c) Routes developed by Seok et al. and Spiccia et al.

Anti-solvent + Excess organic

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

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

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

What are the cation options? Goldshmidt Tolerance factor G. Eperon et al. 2014

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

Influence of Colloids In solution

Influence of Addition of Acid (HI and HBr)

Increased crystallinity and crystal orientation

Microstrain and Charge Carrier Mobility

Crystallinity Matters D. McMeekin et al. 2017 Submitted

A new route for single crystal Growth

Breaking up of colloids

Breaking up of colloids Nature Communications 2016 ( Accepted )

What we think about the mechanism

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

N. Noel et al. EES 2016 In-press

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

Enhanced Stability Perovskite Solar Cells

Thermal stability good B 3.5 C 5 t = 0h t = 0h FA 0.83 Cs 0.17 Pb(I 0.6 Br 0.4 ) 3 MAPb(I 0.6 Br 0.4 ) 3 t = 1h t = 1h t = 2h t = 2h 3.0 4 t = 3h t = 3h Absorption (a.u.) Absorption (a.u.) t = 4h t = 4h 2.5 3 t = 6h t = 6h 2.0 2 1.5 1 1.0 0 400 500 600 700 800 400 500 600 700 800 Wavelength (nm) Wavelength (nm) D. McMeekin et al. Science 2016

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

Inverted Cell Architecture FA 0.85 Cs 0.15 Pb(I 0.9 Br 0.1 ) 3 Ag/Au ZnO nanocrystal SPO: 18.2% PCBM 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 J SC V OC (V) FF PCE (%) Br 0.1 ) 3 (mA cm -2 ) FB-SC 23.27 1.04 0.78 18.9 SPO: 19.3% SC-FB 23.30 1.03 0.76 18.1 J SC V OC (V) FF PCE (%) (mA cm -2 ) FB-SC 23.05 1.08 0.79 19.7 SC-FB 23.15 1.07 0.78 19.2 S. Bai et al. (In preparation) 2017

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.

Sealed vs unsealed

But…

And cheaper…

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

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

Simple 4-T configuration Glass FTO SnO 2 /PCBM Perovskite Spiro-OMeTAD Buffer layer ITO + Ai ITO (80 nm) - (p)a-Si:H (~10nm) (i)a-Si:H (<10nm) (n)c-Si (~200µm) Demonstrates Feasibility for > 25% (i)a-Si:H (<10nm) efficiency (n + )a-Si:H (~30nm) Al D. McMeekin et al. Science 2016 DOI 10.1126/science.aad5845

Perovskite-on-Si Tandem EQE and 1-R 100 90 80 70 EQE and 1-R (%) 60 50 40 30 20 10 0 300 400 500 600 700 800 900 1000 1100 1200 Wavelength (nm) EQE Sum IR HIT2 - Perovskite EQE - 18.57mA IR HIT2 - Silicon EQE - 18.26mA IR HIT 2 - 1-R In collaboration with m. McGehee et al. in Stanford University

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.

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

1.2eV planar devices? 1:1 MAI:SnI2 in DMF? … not so promising morphology. Tin-based materials seem to crystallise very rapidly, during spin-coating Noel et al, EES 2014

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

FAPb 1-x Sn x I 3 : Photoluminescence Sn percentage 0% 1.0 12.5% 25% 37.5% 0.8 PL counts (norm) 50% 62.5% 0.6 75% 87.5% 100% 0.4 0.2 1.55 Eg from absorption(Tauc) (eV) PL peak (BP measured - new samples) (eV) 1.50 0.0 Bandgap (eV) 700 750 800 850 900 950 1000 1050 1.45 Wavelength (nm) 1.40 1.35 1.30 1.25 1.20 0% 12.5% 25% 37.5% 50% 62.5% 75% 87.5% 100% Sn %

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

All perovskite tandems G. Eperon et al. Science 2016

Sn-Pb devices show unprecedented stability

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)

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

Calculated Band-gaps and effective mass

Single Crystal Data G. Volonakis et al. JPCL 2016

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

Test and reliability laboratory Requirements: Climatic testing to IEC61646  -8 5̊ C/85% RH >1000hrs  +85 to -4 0̊ C cycling >200 cycles  “ Full Spectrum ” Light soaking to AM1.5G  3000hrs (not IEC) High UV exposure  Etc etc etc 

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

Proper Encapsulation of Cells Encapsulation selection using 1000hr 85 o C/85% baseline 120 Normalised perovskite Colour Moisture ingress accelerates 100 degradation Intensity (%) 80 60 Control 0 hrs Interlayer 350hrs (140) assembly only Control Cover Glass 40 (115) Interlayer A Perovskite Film B Perovskite layer degradation by moisture ingress 20 after early lamination failure C Module 0 Glass 0 200 400 600 800 1000 1200 Stressing Time (hours)

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