Stability enhancement in organic photovoltaics: in-situ structural/morphological monitoring approach applied to plasmonic devices

Introduction Recent results in bulk heterojunction (BHJ) organic photovoltaic (OPV) devices incorporating metallic nanoparticles (NPs) in the photoactive layer are discussed. Our research focuses on two key aspects: rising the... [ view full abstract ]

Introduction

Recent results in bulk heterojunction (BHJ) organic photovoltaic (OPV) devices incorporating metallic nanoparticles (NPs) in the photoactive layer are discussed. Our research focuses on two key aspects: rising the efficiency and the long-term stability of such low environmental impact, flexible and low cost devices. We take advantage of the ability of metallic NPs to raise the BHJ optical absorption by the excitation of localized surface plasmon resonance to address the efficiency issue. At the same time, in-situ time-resolved characterization is applied for understanding the NPs role in inhibiting the chemical/physical mechanisms driving device degradation.

Methods

Plasmonic devices are studied by an unconventional approach based on time-resolved Energy Dispersive X-ray Reflectivity /Diffraction (EDXR/EDXD) techniques, applied jointly with in-situ atomic force microscopy.

Results and Discussion

We found that the polymer conformational properties are stabilized when the BHJ is doped with NPs, also preserving the donor–acceptor network nanoscale morphology. Furthermore, Au NPs doping results in stabilizing the cathode buried interface, a fact ascribed to a NP-mediated mitigation of photo-oxidation effects. As a result, we obtain an increase in the device performance (by 40%) and a significant enhancement in lifetime (by 3 times) with respect to reference undoped devices. These investigations, also demonstrating the great potential of the structural/morphological cross-monitoring approach in directly observing the nanoscale modifications of the bulk/interface properties, pave the way towards OPVs with improved efficiency and stability.

Figure 1: Time-resolved EDXR and AFM analysis of OPV device incorporating metal NPs, demonstrating a NPs mediated mitigation of the aging effects.

References:

[1] B. Paci, G. Kakavelakis, A. Generosi, J. Wright, C. Ferrero, E. Stratakis, E. Kymakis, Solar Energy Materials & Solar Cells, 159, 617–624, 2017.

[2] B. Paci, D. Bailo, V. Rossi Albertini, J. Wright, C. Ferrero, G. D. Spyropoulos, E. Stratakis, E. Kymakis, Adv. Mater., 25, 4760-4765, 2013.

[3] B. Paci, A. Generosi, V. Rossi Albertini, G. Spyropoulos, E. Stratakis, E.; Kymakis, Nanoscale, 4 (23), 7452 – 7459, 2012.

[4]  B. Paci, A. Generosi, D. Bailo, V. Rossi Albertini, G. Spyropoulos, E. Stratakis, E. Kymakis, Adv. Funct. Mater., 21, 3578-3582, 2011.