Physical processes in photo-electric devices based on organic materials and solution processed ones
Organic solar cells (OPVs) have been receiving growing attention for the last years due to their cheap and easy processing (spin coating, low-temperature annealing), mechanical flexibility, and transparency. The building blocks of the devices – the organic materials have a high absorption coefficient and chemical tunability. Today OPVs approach efficiencies of 20%.
To allow for a deeper understanding of the devices, we assembled a new computer-controlled measurement setup. The system is fully automatic and can measure several electrical properties extending over a wide range of applied voltage, five orders of magnitude of light intensity, and more than 100[K] of ambient temperature, under vacuum.
To understand the physics behind the OPVs and improve them even further one must model them. There are several models for organic heterojunction solar cells. However, some of them are too complicated and hard to solve while others are not always self-consistent. In this research, we measured and modeled several types of OPV devices. We worked with different architectures; the simple bi-layer and the modern bulk heterojunction (BHJ), and with different material families; polymers and small molecules as donors and fullerenes and Non-Fullerene Acceptors (NFAs) as acceptors.
At first, we suggested a general and flexible framework, which allows comparing the relative importance of different physical processes, on equal footing for bi-layer devices. Then we expanded the model to BHJs and added the effect of energetic disorder which is crucial in analyzing organic devices.
Ph.D. Under the supervision of Prof. Nir Tessler.