4.8% efficient poly(3-hexylthiophene)-fullerene derivative (1:0.8) bulk heterojunction photovoltaic devices with plasma treated AgO_x/indium tin oxide anode modification

摘要

We report here an improved efficiency, up to 4.8% with a high fill factor of ～63% under AM 1.5G spectral illumination and 100 mW/cm~2 intensity, for poly(3-hexylthiophene) and [6,6]-phenyl C_(61) butyric acid methyl ester bulk heterojunction photovoltaic (PV) devices with a 1:0.8 weight ratio using surface modifications to the indium tin oxide (ITO) anodes through plasma oxidized silver. Here, an enhanced short-circuit current density was achieved without significant loss in the open-circuit voltage (> 0.6V) nor the fill factor (> 63%), leading to an efficiency jump from 4.4% in the control devices to 4.8% with the surface modified ITO anode. The enhanced short-circuit density is attributed to an interface energy step between the ITO and the polymer hole transporting layer. It has been theorized that the introduction of an interface energy step could alter the charge collection efficiency, resulting in an improved overall efficiency in PV devices. In our study, the current density-voltage characteristics under darkness clearly show an increased current density, especially under forward bias, for the anode treated cell, suggesting the presence of an interface energy step between the ITO and the hole transporting layer with surface modified ITO anodes.