(Vittorio de Nora Award) When Solid State Semiconductor Physics and Devices Meet Photoelectrochemistry: From Growth and Interfacial Processes to Photovoltaics
Authors: Lincot Daniel 
Published: August 2024

I joined the CNRS solid-state physics laboratory near Paris in 1978, to work on the preparation of CdTe solar cells using close space sublimation (CSS) growth process. Thanks to some original discoveries, we were able to achieve a record yield of 10.5% for the time, but this research was gradually abandoned in France and in Europe. Yet it was this method that formed the basis of the technology developed with such success by first solar. So I was on the right track.
However, it was in a different direction that I decided to go: semiconductor photoelectrochemistry, a rapidly developing field at the time. Here too, solar energy remained the backdrop, with the field opened up by Honda’s work on the photoelectrolysis of water. I thus began research into the mechanisms of charge transfer at semiconductor-electrolyte interfaces, keeping CdTe as my study material, enabling me to draw on my knowledge of solid-state devices to guide the analysis of its photoelectrochemical behavior in an original way. Our studies have focused on highlighting the energetic changes at interfaces under illumination during charge transfer reactions towards redox species in competition with corrosion reactions. We have demonstrated the role of adsorption and surface chemistry in these phenomena, with the result that photoelectrochemical properties can be optimized. Photoelectrochemistry is once again a highly topical field with artificial photosynthesis.
In 1980 I discovered that CdTe layers could be deposited electrochemically in a simple beaker, as theorized by F.A. Kröger, without having to use much heavier vacuum processes.The electrochemical deposition of CdTe immediately became one of the major themes of my research, and remained so until the 2000s. The analysis of deposition mechanisms and their relationships to film properties were the subject of numerous publications and theses, with some outstanding results, in particular the synthesis of a new phase such as CdTe2, the study of as-grown semiconducting properties , the demonstration of epitaxial growth.
This work gave rise to two major lines of research with far-reaching consequences. The first concerns the extension of electrochemical synthesis to other compound semiconductors of oxide type, with the discovery of the electrochemical synthesis of ZnO by cathodic reduction in the presence of oxygen, leading to materials of exceptional crystalline quality, suitable for epitaxial deposition. Depending on the experimental conditions, the forms obtained can range from nanocolumns to compact films. These results have opened a new avenue at international level. They led us to introduce them into the photovoltaic field for the formation of TCOs or hybrid matrices for dye cells. The second concerns the electrochemical synthesis of CuInGaSe2 (note CIGS), a ternary semiconductor of major industrial importance to photovoltaics. Initiated in the early 90s, this work involved both fundamental research and the creation of an industrial outlet. It led to the creation of a laboratory dedicated to photovoltaics with EDF in 2002, which succeeded in the creation of a start-up in 2009, NEXCIS, which achieved world-class performance in the field. This adventure has been the subject of a book chapter. Today, it continues with the creation of a new start-up, that I founded in 2021, that is using the electrodeposition technology to manufacture ultra-light, flexible, high-efficiency photovoltaic modules for new applications.
This vision of the fundamental and underestimated interest of solution growth methods (electrochemistry or CBD) for the development of high-quality functional materials, particularly for photovoltaic conversion, has guided my entire scientific approach to date. The emergence of halogenated perovskite cells, also prepared in solution, has recently reinforced this approach as a way forward.
Selected references:
RECOMBINATION AND CHARGE-TRANSFER AT THE ILLUMINATED N-CdTe ELECTROLYTE INTERFACE - SIMPLIFIED KINETIC-MODEL ,LINCOT, D; VEDEL, J, JOURNAL OF ELECTROANALYTICAL CHEMISTRY 220 (1987) 179
MECHANISM OF CHEMICAL BATH DEPOSITION OF CADMIUM-SULFIDE THIN-FILMS IN THE AMMONIA-THIOUREA SYSTEM - IN-SITU KINETIC-STUDY AND MODELIZATION, ORTEGABORGES, R; LINCOT, D, JOURNAL OF THE ELECTROCHEMICAL SOCIETY 140 (1993)3464.
SOLAR-CELLS WITH IMPROVED EFFICIENCY BASED ON ELECTRODEPOSITED COPPER INDIUM DISELENIDE THIN-FILMS, GUILLEMOLES, JF; COWACHE, P; MASSACCESSI, S; THOUIN, L; SANCHEZ, S; LINCOT, D; VEDEL, J., Advanced Materials 6 (1994)379
Mechanistic study of cathodic electrodeposition of zinc oxide and zinc hydroxychloride films from oxygenated aqueous zinc chloride solutions, Peulon, S; Lincot, D , JOURNAL OF THE ELECTROCHEMICAL SOCIETY 145 (1998)864
Solution growth of functional zinc oxide films and nanostructures, Lincot, D., MRS BULLETIN 35(2010) 778
From the Lab to Scaling-up Thin Film Solar Absorbers. Hariklia Deligianni, Lubomyr T. Roamnkiw, Daniel Lincot, Pierre-Philippe Grand. Book Chapter in Advances in Electrochemical Science and Engineering,XVIII (2018)