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

[Image: see text] 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 PC(61)BM. PBDB-T/(3BS)(2)-SiPc LbL devices resulted in PCEs up to 3.3%, with an impressive open-circuit voltage (V(oc)) as high as 1.06 V, which is among the highest V(oc) 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 V(oc). 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.