Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
DOI: https://doi.org/10.29363/nanoge.iperop.2019.021
Publication date: 23rd October 2018
Organic solar cells are the subject of an extensive research effort due to their potential application as cheap, light-weight and flexible energy sources. An important step towards the realization of commercialization is attainment of higher efficiencies and improvements of the scale-up process. Both objectives are possible only through a more complete understanding of factors limiting the device performance. In this talk, I will discuss the nature and origin of the charge recombination mechanisms that govern the J-V characteristics of several blend systems. We employ impedance-photocurrent device analysis (IPDA) to quantitatively characterize the competition between charge extraction and charge recombination under steady state operational conditions. Results from the IPDA technique exhibit significantly improved reliability and self-consistency compared to the open-circuit voltage decay technique (OCVD). IPDA measurements also reveal a significant negative electric field dependence of the bimolecular recombination coefficient in high fill factor devices. Combined with morphological characterization of blend films using TEM, GIWAXS, and resonant soft X-ray scattering (R-SoXS), these results shed light on the morphological and electrical properties that can reduce recombination losses in solution-processed BHJ solar cells. This comprehensive investigation provides insight into factors that govern BHJ organic solar cell performance. The IPDA method can also be applied to investigate charge recombination in perovskite solar cells.