No abstract

Solution processing is the most appealing aspect of organic photovoltaic (OPV) devices. The possibility of printing low‐cost, lightweight, and efficient polymer solar cells (PSC) is the commonly accepted paradigm associated with printable materials deposited as inks using solution‐processing techniques. In addition to slot–die, serigraphy, and flexo/gravure printing, spray coating can be used for photo‐active polymer blends, interface materials for hole and electron extraction, and electrodes. This technique is widely accepted in the industrial world as one of the most suitable for coating thin layers onto virtually any kind of substrate (e.g., glass, metal, plastic) with a degree of conformability insuperable by any other high‐speed coating technique. We present the basic principles governing the mechanisms of atomization, the main techniques adopted for PSCs, the state of the art applications of spray coating for building up each layer of a PSC, and an overview of the perspectives for industrialization.

PSS as hole transport/electron blocking layer in solution-processed organic photovoltaics.

Material layers at electrode/semiconductor interfaces are fundamental for the photovoltaic properties of polymer solar cells. The relationship between open‐circuit voltage (VOC) and the work function (φ) of these interface layers is still a matter of debate. Simulations, together with experiments on over more than 20 cell architectures based on P3HT:PC60BM, enabled us to analyze the physical dependence of VOC on φ. In particular, when the work function of the contacts is well inside the gap we observe that performance depends strongly on even small variations of φ. On the other hand, when it approaches the energy levels of the semiconducting polymers, device operation becomes the most efficient and less sensitive to variations in φ. Furthermore, by varying the Gaussian density of states (DOS) of the active blend we were able to show that VOC performance depends significantly also on the DOS. Our study based on the simultaneous variation of transport layers represents a promising method to optimize the design and performance of polymer solar cells. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 690–699

The use of environmental friendly solvents for the fabrication of solution processed organic photovoltaics is a key issue to scale up the technology. Nowadays however, toxic and harmful chlorinated solvents are largely used in polymer solar cell laboratory research. In this work we successfully reached high solubility and miscibility of the low band gap polymer Poly [[4,8-bis[(2-ethylhexyl)(PBDTTT-E-F, commonly known as PTB7), blended with [6,6]-Phenyl-C71-butyric acid methyl-ester ([70] PCBM fullerene derivative) in a non-chlorinated solvent (Dimethylbenzenes also known as Xylenes). We studied the solar cells realized depositing blend solutions based on various Xylenes (ortho, para and an isomeric mixture from technical grade) achieving high power conversion efficiencies up to 8.7%.