Dr. Uli Lemmer

Institute Director, Innovation Lab - Heidelberg


Digitally Printed Optoelectronic Devices and Systems


R. Eckstein, N. Strobel, J. Lehr, F. Mathies, U. W. Paetzold, G. Hernandez-Sosa U. Lemmer
Light Technology Institute and Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT), Germany
and InnovationLab, Heidelberg, Germany

Recently, we have focused on the development of approaches towards the digital realization of energy harvesting devices and image sensors using digital printing techniques, such as ink-jet printing and aerosol jet printing. Organic photodiodes (OPDs) have in recent years reached a level of performance comparable to their inorganic counterparts. Using additives like PMMA, we were able to tune the transparency and viscosity of a P3HT:PCBM photoactive blend for better processability while at the same time achieving a two-fold enhancement of the detection bandwidth. We have also utilized these techniques for the deposition of suitable dewetting structure for a digitally controlled and mask-free micropatterning. These techniques allow for a reproducible deposition of multilayer devices with high registration accuracies and feature sizes down to a few microns. The OPD devices exhibit specific detectivities of >1E12 Jones over a broad wavelength range (400-750 nm) and maximum responsivities of 0.25 A/W. An entirely printed matrix image sensor composing of 256 individual pixels with an individual active area of ~250 µm × 300 µm was fabricated [1].

Inkjet printing offers also a pathway towards the realization of integrated solar cells for energy harvesting applications. We have deposited triple cation perovskite layers with 10% cesium in a mixed formamidinium/methylammonium lead iodide/bromide composite and have reached a high temperature and moisture stability [2]. A reliable process control over a wide range of perovskite layer thickness from 175 to 780 nm and corresponding grain sizes is achieved by adjusting the drop spacing of the inkjet printer cartridge. A continuous power output at constant voltage, resulting in a power conversion efficiency of 12.9%, is demonstrated.

[1] R. Eckstein et al., Fully Digitally Printed Image Sensor Based on Organic Photodiodes, Adv. Optical Mater. 6, 1701108 (2018).
[2] F. Mathies et al., Inkjet-Printed Triple Cation Perovskite Solar Cells, ACS Appl. Energy Mater. 1, 1834 (2018).


Uli Lemmer received the Diploma degree in Physics from RWTH Aachen University in 1990 and a Ph.D. from the University of Marburg in 1995. From 1995 to 1996, he held a postdoctoral position with the University of Cali fornia at Santa Barbara. He was heading the Organic Optoelectronics group at the University of Munich from 1996 to 2002. In 2002 he was appointed a full Professor and Director of the Light Technology Institute, Karlsruhe Institute of Technology (KIT). He is furthermore heading the device physics competence center within the InnovationLab in Heidelberg since 2011. His research interests are in the field of optoelectronics and the technology and the applications of printable organic and inorganic semiconductors.