Morphology Control of Monomer–Polymer Hybrid Electron Acceptor for Bulk-Heterojunction Solar Cell Based on P3HT and Ti-Alkoxide with Ladder Polymer

We report the morphology control of a nano-phase-separated structure in the photoactive layer (power generation layer) of organic–inorganic hybrid thin-film solar cells to develop highly functional electronic devices for societal applications. Organic and inorganic–organic hybrid bulk heterojunction solar cells offer several advantages, including low manufacturing costs, light weight, mechanical flexibility, and a potential to be recycled because they can be fabricated by coating them on substrates, such as films. In this study, by incorporating the carrier manager ladder polymer BBL as the third component in a conventional two-component power generation layer consisting of P3HT—the conventional polythiophene derivative and titanium alkoxide—we demonstrate that the phase-separated structure of bulk heterojunction solar cells can be controlled. Accordingly, we developed a discontinuous phase-separated structure suitable for charge transport, obtaining an energy conversion efficiency higher than that of the conventional two-component power generation layer. Titanium alkoxide is an electron acceptor and absorbs light with a wavelength lower than 500 nm. It is highly sensitive to LED light sources, including those used in homes and offices. A conversion efficiency of 4.02% under a 1000 lx LED light source was achieved. Hence, high-performance organic–inorganic hybrid bulk heterojunction solar cells with this three-component system can be used in indoor photovoltaic systems.