Cahen has authored over 500 articles, written dozens of book chapters, and holds dozens of patents. Cahen is one of the few Israeli researchers whose H-index exceeds 110.
Bioelectronics and Optoelectronic Materials Cahen contributed significantly to the field of molecular optoelectronics, especially in understanding electron transport through molecules and in using organic molecules to improve the performance of electronic devices, in partnership with Prof. Abraham Shanzer. He showed that chemical modification of semiconductors using organic molecules can control the electronic conduction properties of diodes and solar cells, and demonstrated that this effect exists even when the molecular layer is discontinuous. This opened new possibilities that are now used for interface engineering in organic and inorganic semiconductor devices. Together with Shanzer and Ron Naaman, Cahen developed the Molecular Controlled Semiconductor Resistor, a sensor platform based on a cooperative molecular field effect. This platform is being further developed by various research groups in academia and industry. Furthermore, Cahen was a pioneer in the use of controlled molecular monolayers directly bonded to silicon. He created high-quality silicon-molecular monolayer junctions, allowing for doping within them. Moreover, he and his collaborators demonstrated that small organic molecules can act like thicker insulators, creating metal-insulator-semiconductor (MIS) systems without a physical insulator. He also showed that these discoveries can be used to create new metal-molecule-semiconductor solar cells. Cahen created, built, and tested the first reliable protein monolayer system for solid-state electron transport studies through proteins. He showed (together with prof Mordechai Sheves) that the protein bacteriorhodopsin is a surprisingly efficient electron conductor, even though it lacks that role in nature.. This research was extended to other proteins (azurin, photosynthetic reaction centres and albumins) and has implications for future bioelectronics and electron transfer in proteins. Cahen introduced the concepts of LUSO and HOSO (instead of LUMO and HOMO, where the letter S stands for "System") and corrected the accepted model for describing conduction through molecules. He proposed, with Prof. Antoine Kahn from
Princeton University, using the induced density of surface states model for molecular electronics junctions, thereby identifying non-bonding orbitals at the interface between a molecule and a surface as the site of electron transport.
Chemistry of Photovoltaic Materials Cahen contributed to the study of materials chemistry, particularly in the field of photovoltaic materials, interfaces, and devices. In his early years as an independent researcher, he collaborated closely with Profs. Gary Hodes and Joost Manassen, and the three worked on photoelectrochemical solar cells. He argued that separating photovoltaic conversion from chemical synthesis would always be preferred if efficient electrochemical methods exist that can be carried out in dark conditions. One of Cahen's key achievements is his contribution to "second-generation" solar cells (CIS, CIGS, CdTe). Together with Dr. Rommel Noufi from the NREL, then SERI lab in the USA, he provided a chemical explanation for the then-existing need to heat the cell in an oxygen-rich environment to optimize complex polycrystalline solar cells. He showed, since then that this model has broad applications beyond solar cells, including in organic polycrystalline materials. Additionally, he co-discovered, with Prof H.-W. Schock (Stuttgart) that the growth of thin CIGS layers occurs via a "vapor-liquid-solid" (VLS) mechanism. Cahen also discovered that using ordinary glass, a relatively inexpensive material, is crucial for creating optimal CIGS cells. He found that metastable device structures can be formed in homogeneous materials using an external electric field, and determined that this results from electrical drift of copper ions. It was proven that the mobility of copper ions in CIS and CIGS makes these materials radiation-resistant and stable, thanks to their self-healing properties. Cahen also clarified the paradox by which certain polycrystalline solar cells outperform single-crystal cells. Together with Gary Hodes, he provided guidelines for the stabilization of CdTe solar cells, based on their discovery that cells instability is due to air exposure. Further contributions by Cahen include research on halide perovskite-based solar cells, where he showed (in part with Hodes and Dan Oron) that the halide perovskites can recover from damage, they self-heal. Together with Hodes he also found that they can be stabilized by removing the organic part. He emphasized the importance of their mechanical softness as another expression of the root-cause for their remarkable optoelectronic properties. He also showed that there are chemical limits to device miniaturization due to the fundamental chemical instability of the basic p-n junction.
Mentoring Cahen mentored dozens of students who became faculty members in Israel and worldwide, including: Shahar Richter from Tel Aviv University, Yigal Levin from the Hebrew University, Adi Salomon and Hagai Spaisman from Bar-Ilan University, Eran Edri, Iris Visoly-Fisher and Yevgeny Rakita from Ben-Gurion University of the Negev, Igor Lubomirsky and Omer Yaffe from the Weizmann Institute, Arava Zohar from the Technion, Ellen Moons from Karlstad University, Merlin Bruening from
University of Notre Dame, Lior Sepunaruev from University of California, Santa Barbara, Leonid Chernyak from University of Central Florida, Jamal Gaboun from Bethlehem University, and Shaibal Sarkar from IIT-Bombayia. Others made and make their careers in mainly electronic industries in Israel and abroad. Former postdoctoral fellows and visiting scientists found their way to academic positions on several continents. == Awards ==