Open-circuit voltage dependency on hole-extraction layers in planar heterojunction organic solar cells

摘要

The open-circuit voltage (V_(oc)) dependency on hole-extraction layers (HELs) with different energy levels and mobility was investigated in a single stack heteroj unction subphthalocyanine chloride (SubPc)/C_(60) organic solar cells. The HELs having about 0.2-0.3 eV higher highest occupied molecular orbital (HOMO) level than that of a donor material can significantly enhance the V_(oc) in SubPc/C_(60) device due to a corresponding built-in potential increase. The high mobility of HELs can also increase V_(oc) with increasing J_(sc) according to the simple diode equation. Among all HELs we utilized, N,N,N,N-tetra(biphenyl-4-yl)biphenyl-4,4/-diamine (TBBD) illustrates a largest increase in V_(oc) (from 0.90 to 1.15 V) with an improvement in efficiency compared to a reference SubPc/C_(60) device without HEL. This increase is mainly attributed to easy and rapid extraction of holes by TBBD due to its proper HOMO level and high mobility.