Tutorial 4:
Photoelectrochemical (PEC) vs. Photovoltaic (PV) devices: Fundamental similarities for solar energy conversion

(dedicated to the memory of Prof. Dr. Hans-Joachim Lewerenz who passed away on 24 April 2019)
Prof. em. Dr. Hans-Joachim Lewerenz passed away on 24 April 2019 at the age of 70. We worked together and kept a friendly relationship from 1983 to 2015. Hans-Joachim Lewerenz had left HZB to work on artificial photosynthesis at Caltech (USA) at the same time and left HZB to serve Qatar Foundation in Doha. Joachim Lewerenz was a scientist and department head in the field of renewable energies at HMI and HZB. He was a pioneer in the fields of photoelectrochemistry and photovoltaics, and we profoundly discussed a lot these Similarities and differences between photovoltaics and photoelectrochemistry with particular interest on processes that are relevant in light-induced fuel generation and P2Fuel technology. At IRSEC19 (from 27 to 30 November 2019 in Agadir) I am moderating an educational program or tutorial at the 7th international conference for renewable and sustainable energy dedicated to the memory of Prof. em. Dr. Hans-Joachim Lewerenz.

This tutorial concerns deep understanding and fundamental aspect of PEC device working either in photo-catalytic mode where light-induced electrochemical reaction could produce useful chemicals, such as hydrogen, or destroy organic pollutants (e.g to clean water) or designed in photovoltaic mode such as dye-sensitized solar cell (DSSC; e.g. Grätzel cell) in which a reversible electrochemical process occurs at the interface without altering the electrodes or the electrolyte, in this case, the cell produces electrical power. Both photoelectrochemical (PEC) device and PV devices are fundamentally similar regarding their mode of action (light absorption, charges creation, and their separation. The second part the tutorial we will discuss the similarity between PEC in PV mode and solid-state PV solar cells and bring together physicists and chemists working on “photon” energy conversion devices for a mutual understanding of the processes involving different interfaces such as Semiconductor/electrolyte, Semiconductor/metal and semiconductor/semiconductor. The promising materials for photo-electro-catalysis and water splitting based on bandgap tuning and photo-electrochemical-stability including their characterization and technological application will be discussed during the tutorial.


  • Ahmed Ennaoui, Helmut Tributsch et al. Iron disulfide for solar energy conversion Volume 29, Issue 4, (1993) pages 289-370 – https://doi.org/10.1016/0927-0248(93)90095-K
  • Ahmed Ennaoui and Helmut Tributsch, Energetic characterization of the photoactive FeS2 (pyrite) interface, Solar Energy Materials (now Solar Energy Materials and Solar cells) Volume 14, Issue 6, December 1986, Pages 461-474
  • Michael Grätzel Photovoltaic and photoelectrochemical conversion of solar energy, Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 365(1853) (2007) 993-1005
  • Michael G. Walter; Emily L. Warren; James R. McKone; Shannon W. Boettcher; Qixi Mi; Elizabeth A. Santori; Nathan S. Lewis; Solar Water Splitting Cells. Chem. Rev. 2010, 110, 6446-6473. DOI: 10.1021/cr1002326
  • Hans Joachim Lewerenz and Ian D. Sharp, Concepts of Photoelectrochemical Energy Conversion and Fuel Generation, In “Integrated Solar Fuel Generators”, RSC, 2018

Tutorial Topics:
Introduction to solid-state physics. Band energies, doping, Fermi levels, Materials for photovoltaic and photocatalysis, Standard semiconductor/electrolyte junction, Quasi- Fermi levels, Fermi level penning, electron transfer and surface recombination, band alignments, flat-band potentials, and Mott-Schottky plot analysis, photoelectrochemical reactions (photovoltaic mode, photocatalytic mode, Corrosion), Solar-to-Hydrogen (STH) efficiency, and more depending of the available time and interest.

Prof. Ahmed Ennaoui
Retired from Helmholtz-Zentrum Berlin für Materialien und Energie (HZB)
Actually President of the Scientific Council of IRESEN
(Institut de Recherche en Energie Solaire et Energies Nouvelles, Morocco)