This solution was filtered by a 450-nm membrane and spun to form about 450-nm-thick CdSe film on PEDOT:PSS layer, and then two
drops of CHCl3 solution containing 4 mg/mL P3HT were spun on the earlier CdSe layer. Afterwards, this as-fabricated device was annealed at 150°C for 30 min. Finally, an Al layer (about 100-nm thick) was sputtered for 50 min in a metal mask under 4 Pa of argon environment. This Al layer acted as the cathode in the as-fabricated solar cell device. The resulting solar cell device had a structure of FTO/PEDOT:PSS/P3HT-capped CdSe superstructures:P3HT/Al. Characterizations The sizes and morphologies of CdSe superstructures and P3HT-capped CdSe superstructures were investigated by scanning electron microscopy (SEM) (Hitachi S-4800, Hitachi High-Tech, Minato-ku, Tokyo, Japan) and transmission electron microscopy (TEM) (JEM-2010F, Akt inhibitor JEOL Ltd., Akishima, Tokyo, Japan). The X-ray diffraction (XRD) (Rigaku D/max-g B, Rigaku Corporation, Tokyo, Japan) measurement was carried out using a Cu-Kα radiation source (λ = 1.5418 Å). Fourier transform infrared (FTIR) find more spectra of ligands in CdSe were obtained by measuring pellets of KBr and sample using an FTIR-Raman spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). A UV–vis spectrophotometer and a fluorescence spectrometer
(FP-6600, JASCO Inc., Easton, MD, USA) were used for the optical measurements of CHCl3 solution (0.04 mg/mL) containing CdSe superstructures, P3HT-capped CdSe superstructures, and P3HT, respectively. The thermogravimetric analysis Selleckchem 5-Fluoracil (TGA) measurements of the samples were done using the Discovery TGA instrument (TA Instruments, New Castle, DE, USA) under a nitrogen flow rate of 50 mL/min at the heating rate of 10°C/min from 50°C to 600°C. The photocurrent density-voltage curves of solar cells were measured under illumination (100 mW cm−2) using a computerized Keithley model 2400 source meter unit (Keithley Instruments Inc., Cleveland, OH, USA) and a 300-W xenon lamp (69911, Newport Corporation, Irvine, CA, USA) serving
as the light source. Results and discussion Firstly, the effects of the amount of P3HT on the shapes and phases of CdSe have been investigated. In the absence of P3HT, the CdSe sample has a spherical morphology with a diameter of about 100 nm (Figure 1a). The XRD pattern (Figure 1b) of CdSe superstructures reveals a typical hexagonal wurtzite structure, which is in good agreement with that in literatures [38, 39] and from the Joint Committee on Powder Diffraction Standards (JCPDS) (card number 08–0459). These peaks at 23.901°, 25.354°, 27.080°, 35.107°, 41.968°, 45.788°, and 49.669° are assigned to (100), (002), (101), (102), (110), (103), and (112) planes of the CdSe material, respectively. Importantly, this CdSe sample exhibits a pure hexagonal wurtzite structure.