Simple Inverted Annealing Process to Improve Charge Transport Capability of Organic Photovoltaic Devices with Thick Active Layers

Abstract

The light harvesting capability of organic solar cells is restricted by the thickness of active layers, which is not thick enough to trap all photons and leads to a low device performance. In this paper, an efficient and simple method of inverted annealing process was used to overcome the tradeoff induced by the thickness of bulk heterojunction (BHJ) and fill factor of the devices. Because indene-C60 bisadduct (ICBA) is the globular structure, which is beneficial to its migration in the BHJ network under the driving forces of gravity and solvent volatilization, the redistribution of ICBA during the annealing process of the active layer may optimize the vertical phase separation. Herein, the champion power conversion efficiency of 5.873% was achieved in the inverted organic solar cells owning thick BHJ of poly(3-hexylthiophene):ICBA blend by using the inverted annealing process. This improvement is not only ascribed to the short-circuit current increase originating from the improved photon trapping in a wi...