The first successful organic photovoltaic device was reported by Tang with a PCE of about 1% in a bilayer device. Because the short exciton diffusion length, the PCE of bilayer devices is rather lower. In 1995, Heeger introduced the concept of bulk heterojunction (BHJ) organic solar cells. These cells consist of a unique bicontinuous interpenetrating network of donor and acceptor materials, creating large interfacial areas that facilitate efficient exciton dissociation. Since then, the BHJ structure has become the standard architecture for OSCs. The PCBM, synthesized by Wudl, is the most common acceptor material in the era of fullerene OSCs. The design rules for polymer donors should be compatible with the properties of PCBM. Yu reported a family of narrow bandgap D-A copolymers called PTB, which have shown high efficiency and success in the fullerene OSCs. Due to the limited visible light absorption and morphological instability of fullerene, there has been a significant increase in research on non-fullerene electron acceptors. Zhan created a groundbreaking non-fullerene electron acceptor ITIC, which is the beginning of a new era for non-fullerene OSCs. Later, Zou developed high-performance narrow-bandgap Y6, which significantly boosted the efficiency of OSCs to over 19%. In non-fullerene OSCs, the most commonly used polymer donors are PM6 and D18, which were developed by Hou and Ding.
Biological cells exhibit diverse phenomena induced through linking of chemical reactions of molecules and solid surface contact. It is then a significant topic in the field of chemistry to study phenomena induced through this linking using synthetic systems, which can promote our understanding of biological phenomena and can be applied to the development of novel functions. Silica nanoparticles (SNPs), which are synthetic inorganic materials, are attractive for such purposes, because of their following characteristics: they can adsorb large amounts of molecules on their surfaces, they can aggregate through contact between SNPs as well as contact between molecules and SNPs, and the molecules can be easily removed from solutions by precipitation. The contact of SNP surfaces with molecules then affects chemical reactions of molecules and also behaviors of SNPs. This article describes systems derived from synthetic helical molecules and SNPs, which exhibit notable phenomena including selective adsorption and molecular recognition, equilibrium shift, step kinetics with induction period, precipitation with flow and sweeping, and disaggregation and desorption by sonication, in which the high affinity of helical molecules with SNP surfaces plays important roles. Mechanistic models that explain the phenomena are provided. Possible applications are also discussed, including the separation of molecules, capture of intermediates, the storage and release of molecules, equilibrium shift, clocking, and the translation of mechanical stimulations into chemical reactions.