• Laser Opto Milan4 © 2016 IIT 5078
  • Opto Milan2 © 2016 IIT 5079
  • SEM Opto Milan3 © 2016 IIT 5080

The Advanced Materials for Optoelectronics (AMO) group focuses on investigation of the physics behind low cost "future generation" photovoltaic concepts and on the development of associated optoelectronic devices, with a special emphasis on the role of interfacial optoelectronic mechanisms and the goal of improving device efficiency and stability.

AMO has been active since 2010 in the Center for Nano Science and Technology @PoliMi (CNST) of the Italian Institute of Technology. Since 2012, the group core-activity has been the investigation of solution processable metal halide perovskites, a family of crystalline semiconductors with amazing potential for application in optoelectronic and photonic devices.

Unlike more widely studied inorganic semiconductors, metal halide perovskites have fluctuating ionic structures where tilting, distortions, and polarizability of the lattice strongly affect the optoelectronic properties. This makes the functionality and reliability of perovskite-based devices strongly dependent on the control of the structure-property relationship of the active material and of its response to external stimuli, such as chemical interactions upon interface formation, electric field, light, and environmental agents.

Activities

  • Material Synthesis and Processing. We develop methods for the synthesis and processing of semiconductors with improved optoelectronic properties, while responding to selection criteria which include low cost, durability, scalability and environmental impact (low energy and resource demands, reduced toxicity)
  • Advanced Spectroscopy. By combining optical, vibrational and electronic spectroscopy, we investigate the optoelectronic properties of semiconductors, how they are affected when forming interfaces and how and if they will define the related device's functionalities.
  • Device Fabrication and Characterization. We test our materials mainly for energy and photonic applications. We design, fabricate and characterize optoelectronic devices in order to improve efficiency and stability while understanding their working mechanisms over different length and time scales.

Laboratories

Most AMO Group activities take place in a chemical lab, ARCOLab, and three spectroscopy labs, TRPL-Lab, TA/PEEM Lab & CW Lab. ARCOLab is fully dedicated to the synthesis of materials and the fabrication and testing of perovskite-based devices, whereas our spectroscopy labs are dedicated to steady-state and time-resolved spectroscopies from femtosecond to microsecond time scales, as well as Photo-Emission Electron Microscopy (PEEM). We are in a lively and multidisciplinary Center, which gives us full access to printing tools for device manufacturing, an Electrical Characterization Lab and a Structural and Morphological Characterization lab. As a result, our technical capabilities are as follows:

  • Material synthesis and structural and morphological characterization. ARCOLab is equipped with nitrogen and oxygen lines, a fume hood with a Schlenk line and a rotary evaporator, which allows for basic synthesis processes. Within the shared facilities we count with morphology/structure investigating tools such as SEM, AFM, XRD, vibrational spectroscopy set-ups (Raman and IR) and contact angle measurements.

 

  •  Advanced Spectroscopy. Our labs feature a variety of light sources and flexible set-ups for the study of the photophysical properties of semiconductors.

    -TRPL Lab is dedicated to time-resolved photoluminescence. A tunable ultrafast oscillator (Chameleon, 80 MHz) coupled to an optical parametric oscillator provides excitation from the NIR (950 nm) to UV (350 nm). The resulting photoluminescence can be measured with a time resolution of 1.6 ps in the visible range (Hamamatsu Streak Camera, up to 900 nm), and 1 ns in the IR (TCSPC, up to 1400 nm).

    -CW Lab offers a variety of light sources on CW or low repetition rate mode. These can be coupled with flexible photoluminescence lines and integrating spheres to test our materials under varied illumination conditions, or used in connection with a spectrophotometer (200-2500 nm) and a spectrofluorometer (300 nm-1700 nm). Electro-absorption and charge modulation spectroscopy set-ups are also available. Particularly useful for perovskite research is our Photothermal Deflection Spectroscopy (PDS) set-up, to probe weak sub bandgap absorption up to five orders of magnitude below that at the band-edge.

    -TA/PEEM Lab. This lab hosts a femtosecond laser system dedicated to ultrafast time-resolved spectroscopies, including a transient absorption spectrometer, excitation correlation photoluminescence (ECPL) and optical gain measurements. This laser system is coupled to our Photo-Emission Electron Microscope (tr-PEEM). One particular novelty of our time-resolved systems in this lab is the particularly large range of accessible time delays, over 10 orders of magnitude time-delay (10-13–10-3 s).

    Our optical labs are equipped with vacuum and cryogenic equipment which allows us to perform experiments in a controlled atmosphere and down to 4 K.
  • Fabrication and characterization of perovskite-based devices. ARCOLab is fully equipped to fabricate and characterize solar cells and light-emitting diodes (LED). Starting with an ultrasonic bath, O2 plasma and UV ozone chambers, a spin-coater and hot plates, which allow for a variety of substrate preparation methods, through a Nitrogen filled three-chamber glovebox with a spin coater and hotplates, an organic/inorganic evaporator, a metal evaporator and finishing with an encapsulation process, we are capable of fabrication of devices with different architectures. The laboratory is equipped with a profilometer and an UV-Vis spectrophotometer in order to control immediately the quality of fabricated perovskite films.

Additionally, in ARCOLab we have the equipment necessary to perform a full electrical characterization of solar cells and LEDs. Setup for includes includes a solar simulator with fully automatic sample holder for 16 substrates, a separate system for EQE measurement and a P&O Maximum Power Point Tracker to perform stability tests in controlled environment and temperature. For LEDs characterization, we built a setup consisting of a two-channel sourcemeter and a spectrometer. We possess also an aging chamber with controlled atmosphere, illumination and temperature, which allows us to perform degradation tests on the devices.

In addition, we have access to the Electrical Characterization Lab of CNST which is equipped for the full characterization of devices such as transistors and photodetectors.

Projects

Active Projects:

  • SOPHY- "The role of Softness in the Physics of Defects: Probing Buried Interfaces in Perovskites Optoelectronic Devices" - ERC-2017-COG (2018-2023) – PI: Dr Annamaria Petrozza
  • PERTPV - "Perovskite Thin-film Photovoltaics" - H2020-LCE-07-2017 (2018-2021) – Unit PI: Dr Annamaria Petrozza
  • eScaled - "European School on Artificial Leaf: Electrodes & Devices - Marie Skłodowska Curie Action European Training Network (2018-2022) - Unit PI: Dr Annamaria Petrozza
  • MAESTRO - "Making Perovskites Truly exploitable" - Marie Skłodowska Curie Action European Training Network (2017-2021) - Unit PI: Dr Annamaria Petrozza
  • PERICLeS – “PERovskIte Coherent Light Sources” - H2020-MSCA-IF-2018, PI: Dr Daniele Cortecchia

Past Projects

  • DESTINY - "Dye Sensitized solar cells with enhanced stability" – Marie Curie Initial Training Network (2012-2016). Unit PI: Dr Annamaria Petrozza
  • “Probing Hybrid Interfaces of High Performance Solid-State Solar Cells” The Royal Society International Exchanges Scheme 2012/R2 (2013-2014) - in collaboration with Dr H.J. Snaith (University of Oxford).
  • MESO - "Meso-superstructured Hybrid Solar Cells " - FP7-NMP-2013-SMALL-7 (2013-2016) Unit PI: Dr Annamaria Petrozza
  • “Green nanomaterials for next-generation photovoltaics (GREENS)” - Fondazione Cariplo (2014-2016). Unit PI: Dr Annamaria Petrozza
  • SYNCHRONICS - "Supramolecularly engineered architectures for optoelectronics and photonics: a multi-site initial training action - Innovative Training Networks (2015-2018)
  • IPERLUCE - Fondazione Cariplo (2015-2016)- PI: Annamaria Petrozza

Collaborations

  • Prof Filippo De Angelis (University of Perugia & (ISTM-CNR). Expert in the field of ab initio computer simulations of electronic, structural and optical properties of complex materials, semiconductors and surface-adsorbed molecules and relativistic effects relevant for the description of heavy atoms; all key ingredients for the description of perovskites and hybrid interfaces
  • Prof Ajay Ram Srimath Kandada (Wake Forest University), Expert in advance optical spectroscopy of emerging materials, particularly excitonic systems.