Armantas Melianas received his PhD from Linköping University (Sweden) in 2017 for his work on time-resolved charge motion in organic solar cells. He joined Stanford on October 2017 as a recipient of the prestigious Wallenberg Foundation Postdoctoral Fellowship and is currently working on brain-like computing applications using organic semiconductors.
Honors & Awards
Wallenberg Postdoctoral Fellowship, The Knut and Alice Wallenberg Foundation (2017)
Doctor of Philosophy, Linkoping University (2017)
MSc, Vilnius University, Materials Technology (2012)
BSc, Vilnius University, Physics (2010)
Alberto Salleo, Postdoctoral Faculty Sponsor
Organic Electronics for Neuromorphic Computing
2018; 1 (7): 386-397
View details for DOI 10.1038/s41928-018-0103-3
Charge Transport in Pure and Mixed Phases in Organic Solar Cells
ADVANCED ENERGY MATERIALS
2017; 7 (20): 1700888
View details for DOI 10.1002/aenm.201700888
Photogenerated Carrier Mobility Significantly Exceeds Injected Carrier Mobility in Organic Solar Cells
ADVANCED ENERGY MATERIALS
2017; 7 (9): 1602143
View details for DOI 10.1002/aenm.201602143
Photo-generated carriers lose energy during extraction from polymer-fullerene solar cells
In photovoltaic devices, the photo-generated charge carriers are typically assumed to be in thermal equilibrium with the lattice. In conventional materials, this assumption is experimentally justified as carrier thermalization completes before any significant carrier transport has occurred. Here, we demonstrate by unifying time-resolved optical and electrical experiments and Monte Carlo simulations over an exceptionally wide dynamic range that in the case of organic photovoltaic devices, this assumption is invalid. As the photo-generated carriers are transported to the electrodes, a substantial amount of their energy is lost by continuous thermalization in the disorder broadened density of states. Since thermalization occurs downward in energy, carrier motion is boosted by this process, leading to a time-dependent carrier mobility as confirmed by direct experiments. We identify the time and distance scales relevant for carrier extraction and show that the photo-generated carriers are extracted from the operating device before reaching thermal equilibrium.
View details for DOI 10.1038/ncomms9778
View details for Web of Science ID 000366294700004
View details for PubMedID 26537357
View details for PubMedCentralID PMC4659933
- Dispersion-Dominated Photocurrent in Polymer: Fullerene Solar Cells ADVANCED FUNCTIONAL MATERIALS 2014; 24 (28): 4507-4514
- Automated open-source software for charge transport analysis in single-carrier organic semiconductor diodes ORGANIC ELECTRONICS 2018; 61: 318–28
- Dead Ends Limit Charge Carrier Extraction from All-Polymer Bulk Heterojunction Solar Cells ADVANCED ELECTRONIC MATERIALS 2018; 4 (8)
- Relating open-circuit voltage losses to the active layer morphology and contact selectivity in organic solar cells JOURNAL OF MATERIALS CHEMISTRY A 2018; 6 (26): 12574–81
- Optimized pulsed write schemes improve linearity and write speed for low-power organic neuromorphic devices JOURNAL OF PHYSICS D-APPLIED PHYSICS 2018; 51 (22)
- Thermal annealing reduces geminate recombination in TQ1:N2200 all-polymer solar cells JOURNAL OF MATERIALS CHEMISTRY A 2018; 6 (17): 7428–38
- A fullerene alloy based photovoltaic blend with a glass transition temperature above 200 degrees C JOURNAL OF MATERIALS CHEMISTRY A 2017; 5 (8): 4156-4162
Role of coherence and delocalization in photo-induced electron transfer at organic interfaces
Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.
View details for DOI 10.1038/srep32914
View details for Web of Science ID 000382648800001
View details for PubMedID 27605035
View details for PubMedCentralID PMC5015064
- New method for lateral mapping of bimolecular recombination in thin-film organic solar cells PROGRESS IN PHOTOVOLTAICS 2016; 24 (8): 1096-1108
- Nonequilibrium drift-diffusion model for organic semiconductor devices PHYSICAL REVIEW B 2016; 94 (3)
High-Entropy Mixtures of Pristine Fullerenes for Solution-Processed Transistors and Solar Cells
2015; 27 (45): 7325-?
The solubility of pristine fullerenes can be enhanced by mixing C60 and C70 due to the associated increase in configurational entropy. This "entropic dissolution" allows the preparation of field-effect transistors with an electron mobility of 1 cm(2) V(-1) s(-1) and polymer solar cells with a highly reproducible power-conversion efficiency of 6%, as well as a thermally stable active layer.
View details for DOI 10.1002/adma.201503530
View details for Web of Science ID 000367833200008
View details for PubMedID 26460821
- A New Fullerene-Free Bulk-Heterojunction System for Efficient High-Voltage and High-Fill Factor Solution-Processed Organic Photovoltaics ADVANCED MATERIALS 2015; 27 (11): 1900-?
- Fully-solution-processed organic solar cells with a highly efficient paper-based light trapping element JOURNAL OF MATERIALS CHEMISTRY A 2015; 3 (48): 24289-24296
- Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells POLYMER CHEMISTRY 2015; 6 (42): 7402-7409
- Origin of Reduced Bimolecular Recombination in Blends of Conjugated Polymers and Fullerenes ADVANCED FUNCTIONAL MATERIALS 2013; 23 (34): 4262-4268
Unified Study of Recombination in Polymer:Fullerene Solar Cells Using Transient Absorption and Charge-Extraction Measurements
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2013; 4 (12): 2069-2072
Recombination in the well-performing bulk heterojunction solar cell blend between the conjugated polymer TQ-1 and the substituted fullerene PCBM has been investigated with pump-probe transient absorption and charge extraction of photogenerated carriers (photo-CELIV). Both methods are shown to generate identical and overlapping data under appropriate experimental conditions. The dominant type of recombination is bimolecular with a rate constant of 7 × 10(-12) cm(-3) s(-1). This recombination rate is shown to be fully consistent with solar cell performance. Deviations from an ideal bimolecular recombination process, in this material system only observable at high pump fluences, are explained with a time-dependent charge-carrier mobility, and the implications of such a behavior for device development are discussed.
View details for DOI 10.1021/jz4009745
View details for Web of Science ID 000320979400014
View details for PubMedID 26283254