Presentation on theme: "Jason D. Myers, Sang-Hyun Eom, Vincent Cassidy, and Jiangeng Xue"— Presentation transcript:
1Enhanced Organic Photovoltaic Cell Performance using Transparent Microlens Arrays Jason D. Myers, Sang-Hyun Eom, Vincent Cassidy, and Jiangeng XueDepartment of Materials Science and EngineeringUniversity of FloridaGainesville, FL, USA
2Outline Introduction Enhancement concept Results Conclusions Photovoltaic technologyOrganic photovoltaicsPerformance limitationsEnhancement conceptResultsExperimentalSimulationConclusionsImages courtesy of Global Photonic Energy Corp.
3Solar EnergySunlight is an ubiquitous, clean and abundant energy source.Readily available energy source for:Remote locationsDeveloping nationsOuter space
4Photovoltaic Technology OrganicsInorganicsInexpensive substratesHigh-throughput processingFlexibleEfficiency : 8%Expensive processingHigh installation costsEfficiency: >20% (c-Si), 10-20% (thin film)Image courtesy of Konarka, Inc.
5Organic Photovoltaic (OPV) Basics SubstrateTransparent ElectrodeActive LayersMetal ElectrodeIlluminationAbsorption ≈ 1- e-αdα = absorption coefficientd = light path lengthGlass or plasticActive layer materials can be small molecules, polymers, inorganic nanoparticles, or blendsTwo different materials are required: electron donor and electron acceptorMaterials are generally neat layers or intermixed
7Fundamental Tradeoffs There is a fundamental tradeoff between light absorption and exciton diffusion/charge collection.SubstrateTransparent ElectrodeActive LayersMetal ElectrodeSubstrateTransparent ElectrodeActive LayersMetal ElectrodeSubstrateTransparent ElectrodeActive LayersMetal ElectrodeIncrease layer thickness:Light absorption ↑Charge collection ↓Decrease layer thickness:Light absorption ↓Charge collection ↑
8Transparent Electrode Improvement RoutesDevelop new active materialsImprove device architecturesManipulate light propagation and absorptionSubstrateTransparent ElectrodeActive LayersActive LayersActive LayersMetal Electrode
9Microlens Arrays for OPVs (2)(1)SubstrateTransparent ElectrodeActive Layerspath length > layer thicknesspath length = layer thicknessMetal ElectrodeRefraction due to incident angle and index of refractionSurface reflection into neighboring featuresEffectively increase light absorption without altering active layer
10Array Fabrication (a) Convective self-assembly of PS microspheres UV-glass or SiO2PDMS(a)Convective self-assembly of PS microspheresCure PDMS, make moldScotch tape to remove spheresMold optical adhesive and cure, form array(a)PSPDMS(b)(b)Cured PDMS(c)Concave PDMS mold(c)PS = 100μm(d)SubstrateMicrolens Array(d)Optical AdhesivePDMS mold
11Enhancement is more significant in regions of poor spectral response Experimental ResultsGlassITOAluminumCuPcC60BCPAbsorption ≈ 1- e-αdIf α is small, path length increase is more significantEnhancement is more significant in regions of poor spectral responseCuPcC6080nm30nm60nm8nm100nm
12Results, cont.Enhancement is seen with a variety of active layer materials.Enhancement is also present at all angles of incidence.Small MoleculePolymerHybrid(CuPc/C60)(P3HT:PCBM)(P3HT:CdSe)Enhancement in current30%29%7%GlassITOAluminumP3HT:PCBMθ80nm100nm100nm
13Device Area Dependence Laboratory-scale devices: mm x mmProduction-scale devices: cm x cmGlass80nmITOCuPc40nm70nmC608nmBCP100nmAluminumEnhancement increases with device area
14Ray Tracing Simulations AirDeviceITOGlassBufferIlluminationn = 1Lens layer, n = 1.5n = 1.5, 0.5mm thickn = 2.0, 100nm thickn = 1.7, 100nm thickIn-house codeRays fired at the stackPropagation behavior is trackedMore rays are being absorbed after multiple passes through the device areaExcellent qualitative agreement with experiment
15Large Area Enhancement Small area device:Large area device:Larger devices allow for:increased light trappingmultiple absorption opportunities
16Practical Applications Lens arrays provide large-area enhancementOptical enhancement effect is not specific to one material systemSoft lithography is compatible with roll-to-roll productionImage courtesy of Frederik KrebsVery promising for future development
17ConclusionsControlling light propagation is a viable route for enhancing organic photovoltaic device performance.Enhancement is due to increased path length in active layerMechanisms are compatible with different active materials, and production-scale processing and device sizes.
18AcknowledgementsFunding:NSF CAREER GrantDOE SETPUF OTLXue Group