Description:
We compare the gain in power conversion efficiency (PCE) achieved by inserting either amorphous or crystalline exciton blocking layers at the anode interface for planar (PHJ) and planar-mixed heterojunction (PM-HJ) organic solar cells based on Tetraphenyldibenzoperiflanthene and fullerenes. For PHJ devices, there is a gain of more than 37% for both types of blocking layers, mainly due to an increase in photocurrent, indicating that this gain can be solely ascribed to the exciton blocking effect. A templating effect as proposed in literature for crystalline blocking layers cannot be affirmed. On the contrary, it is shown that there is a connection between the choice of acceptor (C60/C70) and the blocking effect on the anode side. Moreover, we can show that also for PM-HJ devices a remarkable efficiency enhancement is possible. The insertion of suitable blocking layers at the anode interface can alter the effective work function and thus the open-circuit voltage, leading to a maximum PCE of 5.8% in single junction cells.