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The polymer solar cell (PSC) with Ca/Al electrode always suffers from low stability mainly due to the incorporation of oxygen and moisture-sensitive Ca electron-transport interlayer (ETL). To alleviate this problem, air-stable alternatives to Ca ETL are highly desired. Herein, we report two solution-processable, air-stable, effective and inexpensive ETLs based on potassium-neutralized perylene tetracarboxylic derivative (K 4 PTC) and its rGO composite (rGO-K 4 PTC), respectively. These ETL materials were facilely prepared and characterized by means of UV-vis, FL, FTIR, XPS and UPS. Importantly, both ETLs exhibited a low work function (WF) of 4.0 eV, which well matches the LUMO level of fullerene acceptors and allows their use as ETL in PSCs. As a result, the P3HT and PTB7-th-based devices with respective ETL remarkably outperformed those without ETL yielding increases of ∼35% in power conversion efficiencies (PCEs), which indicates good electron-transporting capabilities of K 4 PTC and rGO-K 4 PTC interlayers. The high-performance PSCs with the ETL gave average PCEs of 6.17–6.18% (for PTB7-th:PC 61 BM-based devices) and 7.26% (for PTB7-th:PC 71 BM-based devices), respectively, fairly comparable to those of Ca/Al devices (6.50% and 7.50%). Furthermore, the rGO-K 4 PTC device exhibited stability higher than that of the K 4 PTC device probably due to the fact that the rGO-K 4 PTC layer can provide more efficient protection for the active layer against degradation. Thus, rGO-K 4 PTC layer might be more suitable for real applications as compared to the K 4 PTC layer. [ABSTRACT FROM AUTHOR]

In this work, a facile preparation of Cu-Au bimetallic nanoparticles (NPs) with core-shell nanostructures is reported. Importantly, as-prepared Cu-Au NPs are highly stable, solution-processable and exhibit a broad localized surface plasmon resonance (LSPR) band at long wavelengths of 550–850 nm. Highly efficient plasmonic organic solar cells (OSCs) were fabricated by embedding Cu-Au NPs in an anodic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer. The average power conversion efficiency (PCE) was enhanced from 3.21% to 3.63% for poly(3-hexylthiophene) (P3HT):phenyl-C 61 -butyric acid methyl ester (PC 61 BM) based devices, from 6.51% to 7.13% for poly[(ethylhexyl-thiophenyl)-benzodithiophene -(ethylhexyl)-thienothiophene](PTB7-th):PC 61 BM based devices and from 7.53% to 8.48% for PTB7-th:PC 71 BM based devices, corresponding to 9.5–13.4% PCE improvement. Such an improvement is very comparable to that (12.5%) obtained in those with plasmonic Au NPs but achieved at lower cost. This study thus demonstrates a novel and cost-effective approach to enhance the photovoltaic performance of OSCs, in combination with the broad-band plasmonic Cu-Au bimetallic nanostructures. [ABSTRACT FROM AUTHOR]