"Nano-infused Solar Cells: Quantum - Rice University

“Nano-infused solar cells: quantumdot/polymer and block copolymer approachesProf. Michael S. Wong (mswong@rice.edu)Prof. Rafael Verduzco, Prof. Lisa BiswalDepartment of Chemical and Biomolecular EngineeringRice University, Houston, TXRice Technology ShowcasePower Generation, Storage and TransmissionNassau Bay, TXJuly 29, 2014

Solar cells The first generation: Silicon-based solar cellsTheoretical power conversionefficiency (PCE) limit 33 %Pros: Good PCECons: High costMRS Bulletin, 2008, 33, 355-364 The second generation: Advanced thin film solar cellsPros: Lower costCons: Market share17.0 %120.0 %National Renewable Energy Laboratory (NREL)

The basic facts aboutthe third generation solar cellsIdeal rateChallenge:the morphology insidethe active layer is difficultto controlLightAdvantage:low cost, light weight, easy to process, strong opticalabsorption2Adv. Coll. Interface Sci., 2008, 138, 1-23National Renewable Energy Laboratory (NREL)

5Semiconductor NanomaterialsAt least one feature in 1-100 nanometer (nm; 10-9 m) rangeElectronic StructureSurface PropertiesBulkDonega, C. M.; Chem. Soc. Rev. 2011, 40, 1512-1546.Smith, A. M. et al.; Acc. Chem. Res. 2010, 43, 190-200Liu, G. et al.; Chem. Commun. 2010, 46, 755-757.

6Cadmium Selenide (CdSe) Bulk CdSe– Semiconductor– Fixed Band gap – 1.74 eV– High electron mobility (600 cm2/Vs) CdSe nanoparticles (NPs) 10 nm––––Size dependent variable band gap1.74 eV to 2.75 eV; Visible spectrumDiscrete absorption spectrumWide variety of shapesMadelung O., Crystal and Solid State Physics, Vol. 17, 1982,Springer-Verlag, Berlin.Saunders B.R. et al., Adv. Coll. Interface Sci., 2008, 138, 1-23.Peng X., Adv. Mater. 2003, 14, 459-463.Manna L. et al., J. Am. Chem. Soc., 2000, 122, 12700-12706.Leekumjorn S., Gullapalli S. and Wong M.S. et al., J. Phys.Chem. B, 2012, 116, 13063-13070.Gullapalli S. et al., Nanotechnology, 2012, 23, 495606 (1-10).

7Shapes of CdSe NPs Used for Solar CellsIPH: Inter particle hoppingIPHIPHIPHLeekumjorn S., Gullapalli S. et al., J. Phys. Chem. B, 2012, 116, 13063-13070.Choi C.L. et al., Annu. Rev. Phys. Chem. 2010, 61, 369-389.Saunders B.R. et al., Adv. Coll. Interface Sci., 2008, 138, 1-23.

8CdSe Tetrapod (TP) Solar Cell ApplicationsShape directingagent1CdSe TPs demonstrate thehighest power conversionefficiencies in hybrid solar cells250 nmLong TP: P3HTShort TP: P3HT7308601. Huang J. et al., J. Am. Chem. Soc., 2010, 132, 15866-15868.3.362.3346401.120.82. Saunders B.R. et al., Adv. Coll. Interface Sci., 2008, 138, 1-23.

9New Method to CdSe HNPs1.2.3.4.Cd precursorCd(NO3)2·4H2O(Melting Point: 59.5 C)Selenium PrecursorSe powder inOctadecene (ODE)SurfactantCetyltrimethylammoniumbromide (CTAB)SolventOctadeceneColloidally stablefor 24 monthsHeat@ 10 ̊C /min@ 190 C5 min1.2.CentrifugeRemove solids3.4.Ethanol washCollect cleanedparticlesRedisperse inchloroform (CF)5.Reddish brownclear suspensionin CFReddish browncloudy solution

1050 nm

11General Synthesis Route for ChalcogenidesCdTeCdSAbsorption spectra50 nm50 nmZnSZnSe Synthesis strategy canbe applied to othercompositions Requires optimization50 nm50 nm

12Photovoltaic Performance of CdSe HNPsList of abbreviationsPincident – Incident PowerOpen circuit voltage – VocShort circuit current – Jsc or IscFill Factor - FFPower conversion efficiency – PCESeries Resistance – RsActual hybridsolar cell deviceDevice schematicPCE Isc Voc FFPincidentPhotoactive LayerPCE (%)Jsc (mAcm-2)Voc (V)FF (%)Rs(Ωcm2)Standard QD(90 wt%):P3HT(10 wt%)0.16 0.090.86 0.180.48 0.1438.1 4.527.5 11.5SampleHNP S1HNP(90 wt%):P3HT(10 wt%)0.08 0.021.36 0.090.18 0.0231.6 1.010.7 3.2HNP S2HNP(80 wt%):P3HT(20 wt%)0.10 0.021.34 0.070.23 0.0333.6 1.310.9 3.4

Structures of hybrid solar cellsConventional setupPhotocathodePhotoactive layerBuffer layerInverted setupAgPEDOT:PSS,MEH-PPV : CdSe TPshole t(Biswal group)Lightelectron collecting layer

Multilayer deposition by LB technique1. Start the compression exp.2. Pull up the solid substrateOne-layer3. Keep surface pressure constant2 µmRepeat the dipping and pulling-up transfer process toget the multi-layer stackMulti-layer1 µm4. Dipping backChao et al., in preparation, 2014

New fabrication with short TPs20 nm 1 µmMethodSCLB-SCmixVoc (V) Jsc (mA/cm2)0.700.6900.741.895FF (%)34.134.4MEH-PPV: short TPs 1:3,[MEH-PPV] 2.5 mg/mLLB-SC: LB for 5-layer Spin-coating MEH-PPV LB for 5-layerPCE (%)0.1650.482Chao et al., in preparation, 2014

All-conjugated block copolymers provide molecularcontrol over organic semiconductor interfaces(Verduczo group)liquid crystalsurfaceorderinginteractionsAll-Conjugated Block ated polymer blocksRRacceptorSONnRPNDI-TTONRSOSNC8H17 C8H17SNOSSFOP3HTmSSSmLinking group determinescharge separation andrecombination ratesPFTBTSdonormolecular 10 nmCharge separation at blockcopolymer interfaceOSmesoscale10 – 100 nmOOPTB7eh

All-conjugated block copolymers provide molecularcontrol over organic semiconductor interfacesliquid crystalsurfaceorderinginteractionsAll-Conjugated Block ated polymer blocksRRacceptorSONCharge separation at blockcopolymer interfaceOnSRPNDI-TTONRSOSNC8H17 C8H17SNPFTBTOSSdonorSFOP3HTmSSSmesoscale10 – 100 nmOOPTB7mmolecular 10 nm

P3HT-b-PFTBT block copolymerP3HTC6H13S2.9 eVSSnC8H17 C8H17NSNP3HT-b-PFTBTPFTBT3.2 eVPCBM3.7 eVm4.9 eV5.4 eV6.1 eV Majority P3HT (56 wt % P3HT, 44 wt % PFTBT) Some homopolymer impurities ( 17 wt % P3HT homopolymer) Conjugation across linker between block copolymer (fluorene linker) Large HOMOacceptor LUMOdonor offsetGuo, Gomez, Verduzco et al., Nano Lett., 2013, 13, 2957.

High-temperature processing leads toBlock Copolymer OPVs with near 3% PCE2Light (AM 1.5)Block Copolymer OPV(annealed at 165 oC):2J (mA/cm )0-2-4P3HT/PFTBT 165 CP3HT/PFTBT 100 CP3HT-PFTBT 100 CP3HT-PFTBT 165 C-600.20.40.60.8V (V)11.21.4Guo, Gomez, Verduzco et al., Nano Lett., 2013, 13, 2957.Efficiency :Fill Factor:VOC :JSC:3.1 %0.471.21 V5.28 mA/cm2

"Nano-infused solar cells: quantum dot/polymer and block copolymer approaches. Department of Chemical and Biomolecular Engineering. Rice University, Houston, TX . efficiencies in hybrid solar cells 2. 9 New Method to CdSe HNPs Heat @ 10 ̊C /min. 1. Cd precursor Cd(NO 3) 2 ·4H 2 O (Melting Point: 59.5 C) 2. Selenium Precursor Se powder in