Analyses of PTzNTz Polymer Solar Cells Using ESR Spectroscopy

Abstract

Inverted-type polymer solar cells with semiconducting polymers based on PTzNTz have attracted attention because of its high power conversion efficiency (PCE) and thermal stability. In recent years, the PCE of the polymer solar cells has been remarkably improved. However, the effect of these hole transport layers (HTLs) on PTzNTz solar cells have not yet been completely clarified. Here, we report operand electron spin resonance (ESR) spectroscopy of the PTzNTz layered samples to investigate the deterioration mechanism of the PTzNTz solar cells at a molecular level. We have observed monotonic increases in the ESR intensity of the PTzNTz layered samples, where the increases in the ESR intensity of PTzNTz active layers with WO_x HTL are smaller than those with MoO_x HTL. The present results would be useful to develop further highly efficient and durable polymer solar cells.