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 [email protected]: [email protected] Optoelectronic Devices Group Perovskites Perovskite is a calcium titanium oxide, with the chemical formula CaTiO3. 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 CaTiO3, namely ABX3, are termed perovskites. 1892: 1st 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 I3 First Solar Cells Perovskite solar cells Meso-Al2O3 η =10.9% Meso-TiO2 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 Tc Superconductors Publications Vs Efficiency Perovskite Solar Cells Crystallisation of Perovskite Thin Films Crystallisation of perovskite thin films PbX2+ 3 CH3NH3I CH3NH3PbI3+ 2 CH3NH3X (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) (b) (d) Routes developed by Seok et al. and Spiccia et al. Anti-solvent + Excess organic Excess organic + excess PbI2 3MAI:(PbCl(2-2x)PbI(2x)) 3MAI:PbCl2 2% PbI2 5% PbI2 40% PbI2 100% PbI2 N. Saki et al. Small 2017 (in-press) Excess organic + excess PbI2 3MAI:PbCl2 2% PbI2 5% PbI2 30% PbI2 100% PbI2 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(I1-xBrx)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. H2O/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 3.5 5 B t = 0h FA Cs Pb(I Br ) t = 0h MAPb(I Br ) t = 1h C 0.83 0.17 0.6 0.4 3 t = 1h 0.6 0.4 3 3.0 t = 2h 4 t = 2h t = 3h t = 3h t = 4h t = 4h 2.5 t = 6h 3 t = 6h 2.0 2 Absorption (a.u.) 1.5 Absorption (a.u.) 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 C60 derivative PCBM n-type PCBCB n-type Inverted Cell Architecture FA0.85Cs0.15Pb(I0.9Br0.1)3 Ag/Au ZnO nanocrystal SPO: 18.2% PCBM FA(MA)CsPb(I0.9Br0.1)3 NiO ITO Substrates FA0.79MA0.16Cs0.05Pb(I0.9 J SC V (V) FF PCE (%) (mA cm-2) OC Br0.1)3 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 (V) FF PCE (%) (mA cm-2) OC 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 t80 = 1050 h t80 = 694 h t80 = 20.7 h The devices are aged under full spectrum simulated AM1.5, 76 mWcm-2 average irradiance at VOC 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 2 >$40,000/m Up to 33% efficient <$100/m2 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 SnO2/PCBM Perovskite Spiro-OMeTAD Buffer layer ITO + Air 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 60 R (%) R - 50 40 EQE and 1 and EQE 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 Boccard2, Rongrong Cheacharoen1, Jonathan P. Mailoa3, David P. McMeekin4, Robert L. Z. Hoye3, Colin D. Bailie1, Tomas Leijtens1, Ian Marius Peters3, Maxmillian C. Minichetti1, Nicholas Rolston1, Rohit Prasanna1, Sarah Sofia3, Duncan Harwood5, Wen Ma6, Farhad Moghadam6, Henry J. Snaith4, Tonio Buonassisi3, Zachary C. Holman*2, Stacey F. Bent1, 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 1. After spin-coating 2. After immersion 4. After annealing. in anisole bath 50um 10um 2um FAPb1-xSnxI3: Photoluminescence Sn percentage 1.0 0% 12.5% 25% 0.8 37.5% 50% 62.5% 0.6 75% 87.5% 100% 0.4 PL counts (norm) PL counts 0.2 1.55 Eg from absorption(Tauc) (eV) 1.50 PL peak (BP measured - new samples) (eV) 0.0 700 750 800 850 900 950 1000 10501.45 Wavelength (nm) 1.40 1.35 Bandgap (eV) Bandgap 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 VOC 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% APbX3 single junction becomes a 25.9% APbX3/APbX3 tandem Target: cell with a band gap of 2.06eV and Voc 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 . -85C/̊ 85% RH >1000hrs . +85 to -40C̊ 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 85oC/85% baseline 120 100 Moisture ingress accelerates Colour degradation 80 60 Control Interlayer0 hrs perovskite (140) 350hrs Control Cover Glass assembly only 40 Intensity (%) (115) A Interlayer Perovskite Film B Perovskite layer degradation by moisture ingress 20 after early lamination failure C Normalised 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 Next Steps: Development Through to Manufacturing 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. Evolution of Operational loss in perovskite cells SQ- Limit Loss 1.2 [eV] 1.0 9.7% a-Si 0.8 14.1% 10.9% CdTe 17.9% 0.6 20.1% operation(=MP) 22.1% c-Si GaInP GaAs qV 0.4 – ν h 0.2 qV 1.0 1.2 1.4 1.6 1.8 2.0 S-Q from R.Milo,WIS Absorption Edge (eV) Nayak et al.