Single and double layer bulk heterojunction organic solar cell.
Abstract
Bulk heterojunction photovoltaic device based on the binary organic comprised of P3HT:PCBM
and PTB7:PCBM with weight ratio of 1:1 and 1:1.5 respectively. We used these blends as
a photo-active layer with different structures such as single layer of the P3HT:PCBM and
PTB7:PCBM, as well as top-down and bottom-up as double layers of the two active layers
respectively. These layers were deposited using two different simple and inexpensive techniques
such as spin-coating and roll-to-roll (R2R) under ambient laboratory conditions.
The current density-voltage (J-V) characteristics, optical and morphological properties
were investigated. The J-V characteristics exhibited average of power conversion efficiency
of 2.7% for single binary layer blend and 1.3% of double layer blend. The optical
absorption band of a double layer binary blends was extended better than single layer.
However, the device performance of the double layer was found too low due to poor charge
transport processes in the medium. This is an encouraging development toward achieving
low cost organic photovoltaic devices based on single layer ternary blend active layer.