The Stratakis Lab

The Stratakis Lab

Ultrafast Laser Micro and Nano Processing Laboratory

Applications of Lasers in Photovoltaic and Thermoelectric Devices

Objective: The objective of this activity is the application of laser-based processing, fabrication, and diagnostics in the fields of photovoltaic and thermoelectric devices.

Abstract: Organic (plastic) photovoltaic devices (OPVs) and new generation organo-metal and inorganic halide perovskite absorbers thin-film photovoltaic cells (PSCs) have recently emerged displaying exceptional properties and power conversion efficiencies. OPVs and PSCs have attracted significant attention because they facilitate low-cost solution processing, and are simple to fabricate. Furthermore, OPVs and PSCs can be tuned chemically in order to adjust separately band gap, and energy levels. Finally, all-plastic devices can potentially be recyclable, minimizing their impact on the environment at the end of their life cycle. The research aim of this activity is to exploit laser-based processing and diagnostics techniques in the area of Solar Cells. Over the years, we have focused on the pulsed laser assisted synthesis and functionalization of new types of nanostructures that can be exploited for the OPV cells performance improvement. In particular, enhancement of both the efficiency and stability of bulk heterojunction polymer-fullerene OPV devices is demonstrated by the addition of laser-fabricated Au or Al NPs in either the active layer or the interface between the buffer and the active layers (Figure 1a). On a similar manner, we recently start working on the development of novel PSCs upon following laser assisted crystallization techniques, as well as, by employing different types of hole transport layer polymers (Figure 1b), aiming to enhance photovoltaic performance while optimizing device stability.

Figure 1: (a) J-V characteristics of OPV devices with laser-synthesized Au NPs, embedded into the active layer. (b) J-V characteristics of PSC devices with different types of HTL polymers. The insets depict the device architectures.

In addition, among other techniques, femtosecond time-resolved Transient Absorption Spectroscopy (TAS) is used for studying the fundamental photo-physics and decay dynamics in OPVs and PSCs. Namely, TAS provides important insights on the charge carrier dynamics such as electron-hole injection times and exciton recombination rates that are well known to be directly correlated with the performance of the devices. Figure 2a presents a schematic representation of TAS experimental setup, while Figure 2b depicts a typical optical density (ΔOD) spectrum of a glass/ITO/PEDOT:PSS/CH3NH3PbI3 architecture as a function of wavelength and time from which the charge carrier dynamics are revealed upon following fitting analysis. Notably, the TAS setup in ULMNP Laboratory allows the performance of measurements under dry ambient, as well as, in-situ probing at variable temperatures. This part of the research activity is implemented by a joint effort between the ULMNP Group and the Nanomaterials and Organic Electronics Group of the Center of Materials Technology and Photonics (CEMATEP) of the Hellenic Mediterranean University (HMU), headed by Prof. Emmanuel Kymakis. Our continuous mission is to provide research facilities for state-of-the-art research in the multidisciplinary field of nanotechnology and advanced electronics.

Further information:

Figure 2: (a) Schematic representation of TAS experimental setup. (b) Optical density (ΔOD) transient absorption spectra of a glass/ITO/PEDOT:PSS/CH3NH3PbI3 architecture.

Along similar lines, the application of TAS technique is expanded recently to thermoelectric composite polypropylene-based polymers that contain carbon nanotubes (CNTs). The latter are responsible for generating electrical current upon exposure to temperature differentials. Recent data from our Laboratory reveal that TAS is powerful technique and a figure-of-merit method to explore ultrafast phenomena and relaxation processes that take place within these CNT composite polymers, and thus, providing important information for the design and development of novel configurations with enhanced thermoelectric performance. The characterization of thermoelectric polymers by means of TAS will be implemented within the frame of the European project InComEss.

Active projects: InComEss, LASERGRAPH, PrintWin.

Contact persons: Dr. Emmanuel Stratakis, Dr. Ioannis Konidakis

Project members: Dr. Emmanuel Stratakis, Dr. Ioannis Konidakis, Prof. Costas Fotakis, Dr. Kyriaki Savva, Dr. Efthymis Serpetzoglou.

Collaborators: Prof. Emmanuel Kymakis and Prof. Emmanuel Koudoumas (HMU), Dr. Petra Potschke (IPF-Dresden), Dr. Barbara Paci (ISM-CNR Roma), Dr. Antonios G. Kanaras (University of Southampton), Dr. Christos Chochos (TPCI-NHRF).

Selected publications:

  1. “Nitrogen-doped carbon nanotube/polypropylene composites with negative Seebeck coefficient”, B. Krause, I. Konidakis, M. Arjmand, U. Sandararaj, R. Fuge, M. Liebscher, S. Hampel, M. Klaus, E. Serpetzoglou, E. Stratakis and P. Pötschke, J. Compos. Sci. 4, 14 (2020).
  2. In situ monitoring of the charge carrier dynamics of CH3NH3PbI3 perovskite crystallization process”, E. Serpetzoglou, I. Konidakis, T. Maksudov, A. Panagiotopoulos, E. Kymakis and E. Stratakis, J. Mater. Chem. C 7, 12170 (2019).
  3. Limitations of a polymer-based hole transporting layer for application in planar inverted perovskite solar cells”, M. Petrovic, T. Maksudov, A. Panagiotopoulos, E. Serpetzoglou, I. Konidakis, M.M. Stylianakis, E. Stratakis and E. Kymakis, Nanoscale Adv. 1, 3107 (2019).
  4. “Improved charge carrier dynamics of CH3NH3PbI3 perovskite films synthesized by means of laser-assisted crystallization”, I. Konidakis, T. Maksudov, E. Serpetzoglou, G. Kakavelakis, E. Kymakis and E. Stratakis, ACS Appl. Energy Mater. 1, 5101 (2018).
  5. “α,β-Unsubstituted meso-positioning thienyl BODIPY: a promising electron deficient building block for the development of near infrared (NIR) p-type donor-acceptor (D-A) conjugated polymers”, B.M. Squeo, V.G. Gregoriou, Y. Han, A. Palma-Cando, S. Allard, E. Serpetzoglou, I. Konidakis, E. Stratakis, A. Avgeropoulos, T.D. Anthopoulos, M. Heeney, U. Scherf and C.L. Chochos, J. Mater. Chem. C 6, 4030 (2018).
  6. “Enhancement of the power-conversion efficiency of organic solar cells via unveiling an appropriate rational design strategy in indacenodithiophene-alt-quinoxaline π-conjugated polymers”, C.L. Chochos, R. Singh, V.G. Gregoriou, M. Kim, A. Katsouras, E. Serpetzoglou, I. Konidakis, E. Stratakis, K. Cho and A. Avgeropoulos, ACS Appl. Mater. Interfaces 10, 10236 (2018).
  7. “Improved carrier transport in perovskite solar cells probed by femtosecond transient absorption spectroscopy”, E. Serpetzoglou, I. Konidakis, G. Kakavelakis, T. Maksudov, E. Kymakis and E. Stratakis, ACS Appl. Mater. Interfaces 9, 43910 (2017).
  8. “The role of chemical structure in indacenodithienothiophene-alt-benzothiadiazole copolymers for high performance organic solar cells with improved photo-stability through minimization of burn-in loss”, C.L. Chochos, N. Leclerc, N. Gasparini, N. Zimmerman, E. Tatsi, A. Katsouras, D. Moschovas, E. Serpetzoglou, I. Konidakis, S. Fall, P. Leveque, T. Heiser, M. Spanos, V.G. Gregoriou, E. Stratakis, T. Ameri, C.J. Brabec and A. Avgeropoulos, J. Mater. Chem. A 5, 25064 (2017).