Enhanced efficiency of polymer:fullerene bulk-heterojunction solar cells with the insertion of thin CdS layer near the Al electrode

The insertion layer of cadmium sulfide (CdS) between polymer–fullerene blend and Al electrode is used to enhance the short-circuit current (Isc) and the power conversion efficiency (PCE). The solar cells based on the blend of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and C60 with the function layer of CdS (∼10 nm) shows the open-circuit voltage (Voc) of ∼0.7 V, short-circuit current (Isc) of ∼4.6 mA/cm2, filling factor (FF) of ∼0.28, and the power conversion efficiency (PCE) of ∼5.3% under monochromatic light (532 nm) photoexcitation of about 16.7 mW/cm2. Compared to cells without the CdS layer, the power conversion efficiency increases about an order of magnitude. The thickness of CdS layer was varied from 10 to 40 nm using e-beam deposition, and we obtained optimum current density–voltage characteristics for 10 nm thick CdS layer.