Enhancement of Donor–Acceptor Polymer Bulk Heterojunction Solar Cell Power Conversion Efficiencies by Addition of Au Nanoparticles

Abstract

Golden solar cells: Several positive effects arise from the addition of truncated octahedral Au nanoparticles (ca. 70 nm diameter) to bulk heterojunction (BHJ) photovoltaic cells fabricated from a variety of donor polymers and PC70BM as acceptor (see picture). At the optimized blend ratio of Au nanoparticles (5 wt %) in the active layer, the power conversion efficiency increased for all polymer/PC70BM systems under study.

Optically-enhanced performance of polymer solar cells with low concentration of gold nanorods in the anodic buffer layer

“…Au NRs in the PEDOT:PSS layer reduced the volume of the PEDOT:PSS, which lowered the value of Rs, and diminished the interfaces that holes had to travel through to reach the anode. This would facilitate the movement of holes toward the anode [16]. As Fig.…”

“…It is also possible that Au NRs helped trapping the incident light in the active layer via forward scattering mechanism. Thereby, the number of the photo-generated excitons inside the active layer would be increased [14,16], which would then increase the number of the free charge carriers that were collected by electrodes. This would explain the enhancement in the devices Jsc, and the improvement in the PCE.…”

“…The excited MNPs thereby strongly absorb (near-field effect) and scatter (far-field effect) the incident light, producing an enhancement up to a factor of 100 [3], in the electric field surrounding them [8]. Previous studies showed that the PCE of BHJOSCs was improved considerably by MNPs incorporated into OSC layers either on top of indium tin oxide (ITO) [9][10][11][12], within poly(3,4-ethyl-enedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) [13][14][15], within P3HT:PCBM [16], or with the back electrode [17].…”

“…This is due to their additional role in reducing the device series resistance. However, embedding MNPs in the active layer introduces quenching energy states for the excitons, which reduces the number of free charges carriers that are collected by electrodes [12,16]. Hence, introducing MNPs in the anodic buffer layer (ABL) of OSCs would be a good approach.…”

Organic solar cells with plasmonic layers formed by laser nanofabrication

“…Incorporation of metal nanoparticles (MNPs) with sizes smaller than the wavelengths of light in the AM1.5G solar spectrum to create and utilize surface plasmons for trapping the light into the photonic devices 2, 3 is a promising alternative solution. 4,5 It has been shown that the high contrast between the refractive index of metal and the surrounding medium works much like a very fine waveguide coupling efficiently the light (forward scattering) into the absorber. 6,7 The strong local electric field due to surface plasmons can enhance the exciton dissociation in OPVs contributing positively to power conversion.…”