Improvement of inverted planar heterojunction solar cells efficiency by using KI/Alq3 hybrid exciton blocking layer

Abstract

The exciton blocking layer (EBL) as an interfacial layer is extremely critical in determining the organic photovoltaic cell (OPV) performances. Here, we studied inverted planar heterojunction solar cells PHJ-OPVs with the following configuration ITO/EBL/C60/CuPc/MoO3/Al. Upon the EBL functionality which can act as an exciton blocking layer and allows the electron collection at the cathode, we proposed the insertion of hybrid EBL consisted of KI/Alq3 thin layer. The Alq3 is known as an EBL due to its broad bandgap, whereas we found that when a thin layer of 1 nm of KI is introduced in ITO/Alq3 interface, the KI decomposed during the thermal deposition, and only potassium interacts and diffuses in the Alq3 layer, which effectively enhances the electrons collection at the ITO/C60 interfaces leading to the improvement of open-circuit voltage (Voc), and device power conversion efficiency by 36% than the device using Alq3 alone as EBL.