Integration of light-harvesting complexes into the polymer bulk heterojunction P3HT/PCBM device for efficient photovoltaic cells

Abstract

The major light-harvesting chlorophyll (Chl) a/b-binding protein of photosystem II (LHCIIb) in plants is the most abundant membrane protein on earth. During the evolution of photosynthesis over more than 3.4 billion years, this light harvesting system has developed the most effective membrane protein for harnessing solar energy. Because of its high efficiency in absorbing and transferring solar energy, LHCIIb is becoming more and more attractive for mankind's effort to utilize solar energy. Here, we demonstrate the integration of LHCIIb with a P3HT/PCBM bulk heterojunction, in which a P3HT/PCBM active layer, instead of the “reaction centers” in photosystem II (PSII), absorbs the energy transfer from LHCIIb, consequently enhancing the solar energy utilization effectively in solid-state photovoltaic devices. The electronic integration into devices, achieved by inserting a layer of LHCIIb and then coating with a P3HT/PCBM active layer, can remain stable for several weeks. The energy transfer from LHCIIb to P3HT plays an important role in the increase in photocurrent density and broadens the solar absorption spectrum of the control device. The fabricated photovoltaic cells with an LHCIIb interfacial layer achieved an approximately 30% enhancement in the photocurrent and internal quantum efficiencies. Although the heat inactivation effect of the device limits the optimization of the normal structure, the pre-annealing treatment of the inverted organic photovoltaic (OPV) devices is used to realize an improvement in the photoconversion performance.