Spectroscopic Determination of Charge Formation Efficiency of Organic Photovoltaic Cells

Abstract

The internal quantum efficiency (Φ_IQ) of an organic photovoltaic (OPV) cell is governed by plural processes, i.e., the carrier formation process at the D/A interface and the carrier transfer process toward the collector electrode. Then, Φ_IQ can be decomposed into the carrier formation (Φ_CF) and carrier transfer efficiencies (Φ_CT). By combination of femtosecond time-resolved and electrochemical spectroscopies, we determined absolute values of Φ_CF of F8T2/PC₇₁BM, P3HT/PCBM, and PTB7/PC₇₁BM solar cells. We found that Φ_CF at 400 nm of the F8T2/PC₇₁BM cell is higher than those of the P3HT/PCBM, and PTB7/PC₇₁BM cells, although Φ_IQ at 400 nm is the lowest.

Keywords:

• Organic photovoltaic cell
• carrier formation efficiency
• ultrafast spectroscopy
• electrochemical spectroscopy