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Two solution-processableacceptor–donor–acceptor(A-D-A) structured organic molecules with bithienyl-substituted benzodithiophene(BDTT) as central and donor unit, indenedione (ID) as acceptor unitand end groups, and thiophene (T) or bithiophene (bT) as π-bridges,D1 and D2, are designed and synthesized for the application as donormaterials in organic solar cells (OSCs). Two corresponding moleculeswith alkoxy side chains on BDT, DO1, and DO2 are also synthesizedfor comparison. The four compounds possess broad absorption coveringthe wavelength range 450–740 nm and relatively lower HOMO energylevels from −5.16 to about −5.19 eV. D2 and DO2 withbithiophene π-bridges demonstrate stronger absorbance and higherhole mobilities than the compounds with thiophene π-bridges.The power conversion efficiency (PCE) values of the OSCs based onthe organic compounds/PC70BM (1.5:1, w/w) are 6.75% forD2, 5.67% for D1, 5.11% for DO2, and 4.15% for DO1. The results indicatethat the molecules with thienyl conjugated side chains and bithiopheneπ-bridges show better photovoltaic performance. The PCE of theD2-based OSC are among the highest values in the OSCs based on thesolution-processed organic small molecules. [ABSTRACT FROM AUTHOR]

Abstract: A new star-shaped D–π–A molecule with triphenylamine (TPA) as core and donor unit, octyl cyanoacetate (CA) as end group and acceptor unit, and 2,2′-bithiophene vinylene (bTV) as π bridge, S(TPA-bTV-CA) was designed and synthesized for the application as donor materials in solution-processed bulk-heterojunction organic solar cells (OSCs). The compound is soluble in common organic solvents. The thermal, optical and electrochemical properties of the star molecule were studied. The OSC devices were fabricated by spin-coating the blend solution of the molecule as donor and PC70BM as acceptor (1:3, w/w). The OSC device based on S(TPA-bTV-CA)/PC70BM demonstrated a high open circuit voltage of 0.91V, a short circuit current density of 4.64mA/cm2, a fill factor (FF) of 50%, corresponding to a power conversion efficiency of 2.1%, under the illumination of AM 1.5, 100mW/cm2. [Copyright &y& Elsevier]

Hybrid nanostructured silicon–organic solar cells have been pursued as a low‐cost solution for silicon photovoltaic devices. However, it is difficult for the organic semiconductor, typically poly(3,4‐ethylenedioxythiophene):polystyrene (PEDOT:PSS), to fully cover the nanostructured silicon surface due to the high surface tension of the polymer solution and the small size of the cavities in nanostructured silicon. As a result, the performance of the hybrid solar cells is limited by the defect‐induced surface recombination and poor hole extraction. In this work, an inorganic hole‐transporting layer, copper(I) thiocyanate (CuSCN), is introduced between silicon nanowire (SiNW) and PEDOT:PSS to improve the junction quality. The effect of CuSCN on as‐fabricated SiNW and tetramethylammonium hydroxide (TMAH)‐treated SiNW structures is examined, and it is shown that in both cases CuSCN can well cover the SiNW surface due to the easy penetration of its solution into the silicon nanostructure. As a result, the power conversion efficiency of the solar cells has been dramatically improved from 7.68% to 10.5% for as‐fabricated SiNW‐based‐hybrid cells, and from 10.75% to 12.24% for TMAH‐passivated SiNW‐based‐hybrid cells, suggesting that the double hole‐transporting layer approach can effectively improve the junction quality in hybrid organic‐nanostructured silicon‐based devices. An inorganic hole‐transporting layer, copper(I) thiocyanate (CuSCN), is introduced between silicon nanowire (SiNW) and poly(3,4‐ethylenedioxythiophene):polystyrene (PEDOT:PSS) to improve the junction quality. The power conversion efficiency of the solar cells has been dramatically improved 10.75–12.24%, suggesting that the double hole‐transporting layer approach can effectively improve the junction quality in hybrid organic‐nanostructured silicon based devices. [ABSTRACT FROM AUTHOR]