Mechanical and Electrical Behavior of Organic Solar Cells Probed Through Detailed Morphological Control

One of the main advantages of organic solar cells is their potential to be used in flexible or even stretchable applications. Most research in the field of organic solar cells is focused on materials synthesis, device physics, and the relationship between morphology and the optoelectronic performance. In order for this technology to be commercially competitive, especially for flexible applications, a more complete picture that explores the mechanical properties of organic materials and how they relate to their optoelectronic properties is necessary. This thesis consists of two main research tracks: The first track focuses mainly on the effect of morphology on the mechanical, electrical and optical performance of organic solar cells controlled through varying processing conditions. Two mechanical properties are investigated including the elastic modulus and crack onset strain of P3HT, PCBM and blend (BHJ) films. The second track utilizes the high achievable ductility of organic semiconducting films that is investigated in the first track of the thesis, to create novel solar cell device architectures and to gain insight into the performance and recombination losses of organic solar cells. Processing ductile BHJ films is used to create organic solar cells with controlled level of polarization with both opaque and semi-transparent architectures. Moreover, using the strain-alignment method the efficiency of low and high order P3HT aggregates is probed within the same film to show similar internal quantum efficiency for the two different morphological P3HT domains. This selective probing technique provides significant insight into performance loss mechanisms in organic solar cells.