Layer-by-Layer Organic Photovoltaic Solar Cells Using a Solution-Processed Silicon Phthalocyanine Non-Fullerene Acceptor.

Marie D M Faure,Nicole A Rice,Chloé Dindault,Benoît H Lessard

doi:10.1021/acsomega.1c05715

Abstract

Silicon phthalocyanines (SiPcs) are promising, inexpensive, and easy to synthesize non-fullerene acceptor (NFA) candidates for all-solution sequentially processed layer-by-layer (LbL) organic photovoltaic (OPV) devices. Here, we report the use of bis(tri-n-butylsilyl oxide) SiPc ((3BS)2-SiPc) paired with poly(3-hexylthiophene) (P3HT) and poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))] (PBDB-T) donors in an LbL OPV structure. Using a direct architecture, P3HT/(3BS)2-SiPc LbL devices show power conversion efficiencies (PCEs) up to 3.0%, which is comparable or better than the corresponding bulk heterojunction (BHJ) devices with either (3BS)2-SiPc or PC61BM. PBDB-T/(3BS)2-SiPc LbL devices resulted in PCEs up to 3.3%, with an impressive open-circuit voltage (Voc) as high as 1.06 V, which is among the highest Voc obtained employing the LbL approach. We also compared devices incorporating vanadium oxide (VOx) or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as a hole transporting layer and found that VOx modified the donor layer morphology and led to improved Voc. Probing the composition as a function of film layer depths revealed a similar distribution of active material for both BHJ and LbL structures when using (3BS)2-SiPc as an NFA. These findings suggest that (3BS)2-SiPc is a promising NFA that can be processed using the LbL technique, an inherently easier fabrication methodology for large-area production of OPVs.

Highlights

Organic photovoltaics (OPVs) are capable of rivaling the performance of other solar technologies, with state-of-the-art OPV devices exhibiting power conversion efficiencies (PCEs) as high as 18%.1−3 This improved efficiency, combined with the potential of semitransparency, flexibility, and low-cost mass production through techniques such as roll-to-roll printing, has been the main reason for continuing research interest.[4,5] for OPVs to become competitive, the selection of active materials, their synthetic complexity, as well as the processes to fabricate and assemble the different layers, is critical
We investigated the use of the synthetically facile phthalocyanine derivative (3BS)2-SiPc as an non-fullerene acceptors (NFAs) in sequentially all-solution-processed LbL OPV devices
hole transporting layer (HTL), PEDOT:PSS and vanadium oxide (VOx), were investigated as HTLs with VOx found to facilitate favorable changes in the P3HT film morphology, which resulted in improved FF and Voc for (3BS)2-SiPc-based devices processed by LbL

Summary

■ INTRODUCTION

Organic photovoltaics (OPVs) are capable of rivaling the performance of other solar technologies, with state-of-the-art OPV devices exhibiting power conversion efficiencies (PCEs) as high as 18%.1−3 This improved efficiency, combined with the potential of semitransparency, flexibility, and low-cost mass production through techniques such as roll-to-roll printing, has been the main reason for continuing research interest.[4,5] for OPVs to become competitive, the selection of active materials, their synthetic complexity, as well as the processes to fabricate and assemble the different layers, is critical. Incorporation of (3BS)2-SiPc as the acceptor in BHJ devices with either HTL led to similar PCE performances compared to the baseline devices with a PC61BM acceptor, which represents a significant improvement over initial reports using (3BS)2SiPc as an NFA in direct BHJ device configurations.[41] While our PC61BM-based devices consistently achieved more favorable FF, the use of (3BS)2-SiPc resulted in higher Voc (Table 1). Analogous to BHJ results, the use of VOx resulted in more consistent (3BS)2-SiPc-based LbL devices (Figure 2c and Table 1), suggesting that for P3HT devices, a VOx HTL layer can result in superior OPV performances compared to PEDOT:PSS-based devices. UV−vis absorption spectra for the two donor−acceptor films (Figure 6c) have matching trends, with an intense absorption peak just before 700 nm These results demonstrate that (3BS)2-SiPc is an extremely versatile NFA for LbL processing, capable of replicating BHJ performances in different polymer systems

■ CONCLUSIONS

Findings

■ REFERENCES