Properties of Bulk Heterojunction Organic Solar Cells with LiF Buffer Layer at Various Concentrations of Active Layer

Abstract

We fabricated organic solar cells (OSCs) using poly[2,6(4,4’bis(ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-alt-(1,3-(5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione))] (PD-TSTPD) and (6,6)-phenyl-C₇₁ butyric acid methyl ester (PC₇₁BM) active materials. PDTSTPD and PC₇₁BM solutions for the active layer were mixed at concentration ratios of 1:1, 1:2, 1:3, and 1:4 wt%, respectively. The effects of OSCs at various concentrations of active layer on the electrical and morphological properties of the device were investigated. The performance of the OSC at a concentration ratio of 1:3 wt% showed the best electrical properties among the prepared samples, indicating that the maximum short circuit current density (J_sc), open circuit voltage (V_oc) and power conversion efficiency (PCE) values were about 6.9 mA/cm², 0.849 V and 2.3%, respectively. PDTSTPD:PC₇₁BM active layer with a concentration ratio of 1:3 wt% showed smooth film roughness compared to the other prepared samples, which may lead to an improvement of the electron injection efficiency into the cathode electrode.

Keywords:

• Organic solar cell
• LiF
• PDTSTPD
• PC₇₁BM
• concentration ratio
• power conversion efficiency

Funding

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST : 2011-0015835).