Enhanced performance and stability of ternary organic solar cells based on fullerene acceptors and PEIE dipole interfacial transport layer*

The limiting stability of organic solar cells (OSCs) is the main barrier to commercial use. Ternary blend strategy and usage of the dipole interfacial transport layer contribute to achieving the required device stability and improving the performance of OSCs. The fullerene acceptors have played a key role in the bulk heterojunction OSCs due to advantages such as ultrafast photo-induced electron transfer from polymer and strong absorption in the visible region. In this presentation, we demonstrate the efficiency of ternary OSCs having PC61BM into binary blend PTB7-Th:PC71BM on a low temperature processed dipole interfacial polyethylenimine ethoxylated (PEIE) electron transport layer (ETL). The Impedance measurements confirm that ternary blend OSC device has faster charge transfer and high recombination resistance at the interface than binary blend OSC devices. Therefore, a high PCE of 7.8 % with 5 % increased current density (J_sc) due to complementary absorption of PC61BM was achieved for the ternary blend, which is 10% higher than the binary device. The stability of encapsulated OSCs was tested after storing these in the ambient environment. The ternary and binary OSCs retained almost 90% and 85% of their initial performances after 60 days, respectively.