I joined the theory group at the Max Planck Institute for Polymer Research as a Postdoctoral fellow in March 2018. In my current research, I am focusing on the design of non-fullerene acceptors for organic sollar cells.
I obtained my PhD in Physics from Moscow State University in 2017, under the supervision of Prof. V. Ivanov. My research addressed a hybrid simulation scheme which combines the fast equilibration on long times and large scales and the ability to account for the details of the chemical structure of molecules. As an intern, I worked in Schlumberger Moscow Research Center on a project aimed to improve the estimation methods of storage capacity and hydrocarbon flow through nanopores. I obtained my Diploma with Honours in Condensed Matter Physics (Polymer Physics) from Moscow State University in 2014.
Reduced bimolecular charge recombination in efficient organic solar cells comprising non-fullerene acceptors
Y. Wu, Y. Li, B. van der Zee, W. Liu, A. Markina, H. Fan, H. Yang, C. Cui, Y. Li, P. W. M. Blom, D. Andrienko, G.-J. A. H. Wetzelaer
Chemical design rules for non-fullerene acceptors in organic solar cells
A. Markina, K.-H. Lin, W. Liu, C. Poelking, Y. Firdaus, D. R. Villalva, J. I. Khan, S. H. K. Paleti, G. T. Harrison, J. Gorenflot, W. Zhang, S. De Wolf, I. McCulloch, T. D. Anthopoulos, D. Baran, F. Laquai, D. Andrienko
Adv. Energy Mater.,
Efficiencies of organic solar cells have practically doubled since the development of non-fullerene acceptors (NFAs). However generic chemical design rules for donor-NFA combinations are still needed. Such rules are proposed by analyzing inhomogeneous electrostatic fields at the donor–acceptor interface. It is shown that an acceptor–donor–acceptor molecular architecture and molecular alignment parallel to the interface results in energy level bending that destabilizes the charge transfer state thus promoting its dissociation into free charges. By analyzing a series of PCE10:NFA solar cells with NFAs including Y6 IEICO and ITIC as well as their halogenated derivatives it is suggested that the molecular quadrupole moment of 75 Debye A balances the losses in the open circuit voltage and gains in charge generation efficiency.
Impact of Acceptor Quadrupole Moment on Charge Generation and Recombination in Blends of IDT-Based Non-Fullerene Acceptors with PCE10 as Donor Polymer
J. I. Khan, M. A. Alamoudi, N. Chaturvedi, R. S. Ashraf, M. N. Nabi, A. Markina, W. Liu, T. A. Dela Pena, W. Zhang, W. Alsufyani, D. Andrienko, I. McCulloch, F. Laquai
Adv. Energy Mater.,
Advancing non-fullerene acceptor (NFA) organic photovoltaics requires the mitigation of the efficiency-limiting processes. Acceptor end-group and side-chain engineering are two handles to tune properties and a better understanding of their specific impact on the photophysics could facilitate a more guided acceptor design. Here the device performance energetic landscape and photophysics of rhodanine and dicyanovinyl end-capped IDT-based NFAs namely O-IDTBR and O-IDTBCN in PCE10-based solar cells are compared by transient optical and electro-optical spectroscopy techniques and density functional theory calculations. It is revealed how the acceptors’ quadrupole moments affect the interfacial energetic landscape in turn causing differences in exciton quenching charge dissociation efficiencies and geminate versus non-geminate recombination losses. More precisely it is found that the open circuit voltage (VOC) is controlled by the acceptors’ electron affinity (EA) while geminate and non-geminate recombination and the field dependence of charge generation rely on the acceptors’ quadrupole moments. The kinetic parameters and yields of all processes are determined and it is demonstrated that they can reproduce the performance differences of the devices’ current–voltage characteristics in carrier drift-diffusion simulations. The results provide insight into the impact of the energetic landscape specifically the role of the quadrupole moment of the acceptor beyond trivial considerations of the donor–acceptor energy offsets.
N-Doping improves charge transport and morphology in the organic non-fullerene acceptor O-IDTBR
A. F. Paterson, R. Li, A. Markina, L. Tsetseris, S. MacPhee, H. Faber, A.-H. Emwas, J. Panidi, H. Bristow, A. Wadsworth, D. Baran, D. Andrienko, M. Heeney, I. McCulloch, T. D. Anthopoulos
J. Mater. Chem. C,
Doping improves critical performances metrics in electronic devices. Research into n-doped organic small molecules is comparatively limited because of a historical combined lack of available n-dopants and unfavourable microstructural effects. This prevents further advancement of existing materials such as non-fullerene acceptors (NFAs) that have already shown great promise for (opto)electronic devices: from record-efficiency organic photovoltaics to promising semiconductors for n channel organic thin-film transistors. Here we show that several molecular n dopants namely [12-b:2'1'-d]benzo[i][2.5]benzodiazocine potassium triflate adduct (DMBI-BDZC) tetra-n-butylammonium fluoride (TBAF) and 4-(23-dihydro-13-dimethyl-1H-benzimidazol-2-yl)-NN-dimethylbenzenamine (N-DMBI) improve charge transport properties in the NFA O-IDTBR and increase the electron charge carrier mobility to over 1 cm2/Vs in thin-film transistors. By combining complementary experimental techniques with computer simulations of doping and charge dynamics we show that improved charge transport arises from synergistic effects of n-type doping and morphological changes. Specifically a new previously unreported dopant-induced packing orientation results in one of the highest electron mobility values reported to-date for an NFA molecule. Overall this work underpins an important mechanism on dopant-interactions and their impact on morphology showing that dopant induced packing orientation morphology and preferential phase is a key part of the charge transport enhancement process in doped organic systems – rather than a hinderance.
Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells
S. Karuthedath, J. Gorenflot, Y. Firdaus N. Chaturvedi, C. S. P. De Castro, G. T. Harrison, J. I. Khan, A. Markina, A. H. Balawi, T. A. D. Pena, W. Liu, R.-Z. Liang, A. Sharma, S. H. K. Paleti, W. Zhang, Y. Lin, E. Alarousu, D. H. Anjum, P. M. Beaujuge, S. De Wolf, I. McCulloch, T. D. Anthopoulos, D. Baran, D. Andrienko, F. Laquai
In bulk heterojunction (BHJ) organic solar cells (OSCs) both the electron affinity (EA) and ionization energy (IE) offsets at the donor–acceptor interface should equally control exciton dissociation. Here we demonstrate that in low-bandgap non-fullerene acceptor (NFA) BHJs ultrafast donor-to-acceptor energy transfer precedes hole transfer from the acceptor to the donor and thus renders the EA offset virtually unimportant. Moreover sizeable bulk IE offsets of about 0.5 eV are needed for efficient charge transfer and high internal quantum efficiencies since energy level bending at the donor–NFA interface caused by the acceptors’ quadrupole moments prevents efficient exciton-to-charge-transfer state conversion at low IE offsets. The same bending however is the origin of the barrier-less charge transfer state to free charge conversion. Our results provide a comprehensive picture of the photophysics of NFA-based blends and show that sizeable bulk IE offsets are essential to design efficient BHJ OSCs based on low-bandgap NFAs.
Charge Photogeneration in Non-Fullerene Organic Solar Cells: Influence of Excess Energy and Electrostatic Interactions
M. Saladina, P. S. Marques, A. Markina, S. Karuthedath, C. Woepke, C. Goehler, Y. Chen, M. Allain, P. Blanchard, C. Cabanetos, D. Andrienko, F. Laquai, J. Gorenflot, C. Deibel
Adv. Funct. Mater.,
In organic solar cells photogenerated singlet excitons form charge transfer (CT) complexes which subsequently split into free charge carriers. Here we consider the contributions of excess energy and molecular quadrupole moments to the charge separation process. We investigate charge photogeneration in two separate bulk heterojunction systems consisting of the polymer donor PTB7-Th and two non-fullerene acceptors ITIC and h-ITIC. CT state dissociation in these donor--acceptor systems is monitored by charge density decay dynamics obtained from transient absorption experiments. We study the electric field dependence of charge carrier generation at different excitation energies by time delayed collection field (TDCF) and sensitive steady-state photocurrent measurements. Upon excitation below the optical gap free charge carrier generation becomes less field dependent with increasing photon energy which challenges the view of charge photogeneration proceeding through energetically lowest CT states. We determine the average distance between electron--hole pairs at the donor--acceptor interface from empirical fits to the TDCF data. The delocalisation of CT states is larger in PTB7-Th:ITIC the system with larger molecular quadrupole moment indicating the sizeable effect of the electrostatic potential at the donor--acceptor interface on the dissociation of CT complexes.
Long-range exciton diffusion in molecular non-fullerene acceptors
Y. Firdaus, V. M. Le Corre, S. Karuthedath, W. Liu, A. Markina, W. Huang, S. Chattopadhyay, M. M. Nahid, M. I. Nugraha, Y. Lin, A. Seitkhan, A. Basu, W. Zhang, I. McCulloch, H. Ade, J. Labram, F. Laquai, D. Andrienko, L. J. A. Koster, T. D. Anthopoulos
The short exciton diffusion length associated with most classical organic semiconductors used in organic photovoltaics (5-20 nm) imposes severe limits on the maximum size of the donor and acceptor domains within the photoactive layer of the cell. Identifying materials that are able to transport excitons over longer distances can help advancing our understanding and lead to solar cells with higher efficiency. Here we measure the exciton diffusion length in a wide range of nonfullerene acceptor molecules using two different experimental techniques based on photocurrent and ultrafast spectroscopy measurements. The acceptors exhibit balanced ambipolar charge transport and surprisingly long exciton diffusion lengths in the range of 20 to 47 nm. With the aid of quantum-chemical calculations we are able to rationalize the exciton dynamics and draw basic chemical design rules particularly on the importance of the end-group substituent on the crystal packing of nonfullerene acceptors.
Barrierless Free Charge Generation in the High-Performance PM6:Y6 Bulk Heterojunction Non-Fullerene Solar Cell
L. Perdigon-Toro, H. Zhang, A. Markina, J. Yuan, C. M. Wolff, M. Stolterfoht, Y. Zou, F. Gao, D. Andrienko, S. Shoaee, D. Neher
Organic solar cells (OSCs) are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein we thoroughly investigate free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 as a function of internal field temperature and excitation energy. Results show that generation is essentially barrierless with near-unity efficiency regardless of excitation energy. Efficient generation is maintained over a wide temperature range down to 100 K despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA measurements of the energetic disorder and theoretical modelling suggest that charge generation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier. This field also repels charges from donor-acceptor interfaces reducing non-geminate recombination.