Release Time:2019-03-09  Hits:

Indexed by: Journal Article

Date of Publication: 2013-11-13

Journal: ACS APPLIED MATERIALS & INTERFACES

Included Journals: Scopus、PubMed、EI、SCIE

Volume: 5

Issue: 21

Page Number: 11093-11100

ISSN: 1944-8244

Key Words: bulk heterojunction solar cells; n-type semiconductor; perylene diimides; liquid crystalline; space charge limited current

Abstract: In this work, we propose the application of liquid crystalline acceptors as a potential means to improve the performances of bulk heterojunction (BHJ) organic solar cells. LC-1, a structurally-simple perylene diimide (PDI), has been adopted as a model for thorough investigation. It exhibits a broad temperature range of liquid crystalline (LC) phase from 41 degrees C to 158 degrees C, and its LC properties have been characterized by differental scanning calorimetry (DSC), polarization optical microscopy (POM), and X-ray diffraction (XRD). The BHJ devices, using P3HT:LC-1 (1:2) as an organic photovoltaic active layer undergoing thermal annealing at 120 degrees C, shows an optimized efficiency of 0.94 %. By contrast, the devices based on PDI-1, a nonliquid crystalline PDI counterpart, only obtain a much lower efficiency of 0.22%. Atomic force microscopy (AFM) images confirm that the active layers composed of P3HT:LC-1 have smooth and ordered morphology. In space charge limited current (SCLC) devices fabricated via a spin-coating technique, LC-1 shows the intrinsic electron mobility of 2.85 x 10(-4) CM2/V s) (at 0.3 MV/cm) which is almost 5 times that of PDI-1 (5.83 X 10(-5) cm(2)/(V s)) under the same conditions for thermal annealing at 120 degrees C.