Special Talk: Ternary Sensitization of Organic Solar Cells, a Multifunctional Concept to Boost Power Conversion Efficiency

Ternary Sensitization of Organic Solar Cells, a Multifunctional Concept to Boost Power Conversion Efficiency

  • Dr. Tayebeh Ameri
  • 11 Aug 2018, 11:30 a.m.
  • Lecture Hall

The unique selling points of organic photovoltaics (OPVs), such as excellent light harvesting capability, freedom of form, color and transparency, environmental friendliness, easy scalability and lower manufacturing costs based on roll-to-roll printing methods, position this technology for the mobile power market, and this most properly reflects the state of the art in commercialization. An important milestone towards OPV commercialization has been surpassed by reaching a power conversion efficiency (PCE) of over 13%. However, despite the significant improvements achieved, the PCE of OPV has to be increased to compete with commercial inorganic solar cells. The main limitation is due to the intrinsic narrow absorption window (~100-200 nm) of polymers compared to inorganic semiconductors such as Si, which makes it challenging to fully cover the solar spectrum with a single junction device. Furthermore, due to the low mobility of the photoactive materials, organic solar cells present a limited thickness, typically around 100 nm that dramatically limits light harvesting. To overcome the absorption limitation, ternary blend organic solar cells represent one of the dominant strategies that has been explored in the last decade. The outstanding advantage of ternary blends consists of maintaining the simplicity of the processing conditions used for single active layer devices. Moreover, all the optimization strategies developed for binary cells can be also effectively applied for ternary solar cells. In this elegant configuration all three photovoltaic parameters (VOC, JSC, FF) can be tackled simultaneously or individually by optimizing the ratio between the three materials used in the photoactive layer. In this presentation, we will discuss the achieved results in details for various prototype organic ternary systems with a central focus on the fundamental complexity of microstructure and charge transport mechanisms. Importantly, we will explain the key issues that result in modified recombination mechanisms and consequently improved FF and VOC in high efficiency ternary solar cells.