interface ͉ photovoltaic ͉ solar energy

We report the fabrication of organic bulk-heterojunction solar cells based, for the first time, on squaraine/PCBM blends. The most efficient device, solution-processed in air, exhibits J(sc) = 5.70 mA/cm(2), V(oc) = 0.62 V, fill-factor = 0.35, and power conversion efficiency = 1.24%, one of the highest to date for a small molecule solution-processed bulk-heterojunction cell.

No abstract

The effects of anode/active layer interface modification in bulk‐heterojunction organic photovoltaic (OPV) cells is investigated using poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and/or a hole‐transporting/electron‐blocking blend of 4,4′‐bis[(p‐trichlorosilylpropylphenyl)‐phenylamino]biphenyl (TPDSi2) and poly[9,9‐dioctylfluorene‐co‐N‐[4‐(3‐methylpropyl)]‐diphenylamine] (TFB) as interfacial layers (IFLs). Current–voltage data in the dark and AM1.5G light show that the TPDSi2:TFB IFL yields MDMO‐PPV:PCBM OPVs with substantially increased open‐circuit voltage (Voc), power conversion efficiency, and thermal stability versus devices having no IFL or PEDOT:PSS. Using PEDOT:PSS and TPDSi2:TFB together in the same cell greatly reduces dark current and produces the highest Voc (0.91 V) by combining the electron‐blocking effects of both layers. ITO anode pre‐treatment was investigated by X‐ray photoelectron spectroscopy to understand why oxygen plasma, UV ozone, and solvent cleaning markedly affect cell response in combination with each IFL. O2 plasma and UV ozone treatment most effectively clean the ITO surface and are found most effective in preparing the surface for PEDOT:PSS deposition; UV ozone produces optimum solar cells with the TPDSi2:TFB IFL. Solvent cleaning leaves significant residual carbon contamination on the ITO and is best followed by O2 plasma or UV ozone treatment.

The aims of this paper are twofold: first, to gain a fuller understanding of factors that foster community cohesion and contribute to the residents' social and economic well‐being; and, second, to move beyond previous research that used larger spatial units such as states, counties, or aggregates of counties and to focus instead on American small towns (population 2,500–20,000). The data on small towns are drawn from public‐use files and from confidential microdata from various economic censuses. From these sources we construct measures of locally oriented firms, self‐employment, business establishments that serve as gathering places, and associations. The local capitalism and civic engagement variables generally perform as hypothesized; in some cases they are related quite strongly to civic welfare outcomes such as income levels, poverty rates, and nonmigration rates. We discuss the advantages and disadvantages of working with place‐level data and suggest some strategies for subsequent work on small towns and other incorporated places.