The challenge and opportunity of organic semiconductors in photocatalysis

Employing organic semiconductors to drive photocatalytic processes for chemical fuel production and pollutant degradation is a viable pathway for tackling the energy crisis and environmental pollution. In this review, we summarize the development of organic semiconductor photocatalysis so far and propose the future vision of organic semiconductors as state-of-the-art photocatalysts in practical applications. Compared to inorganic semiconductors, organic semiconductors display a large absorption coefficient and easily tunable topological and electronic structures, which set them apart from ordinary inorganic photocatalysts. However, the chemical instability, high exciton dissociation energy and low charge carrier mobility of organic semiconductors are the major obstacles to the improvement of their photocatalytic activity. Obviously, the opportunity and challenge coexist in the development of organic semiconductor photocatalysis. In light of this, we systematically compare the merits and shortcomings of organic semiconductors for heterogeneous photocatalysis and enumerate some feasible approaches to overcoming the bottlenecks hindering their photocatalytic performance. By carefully considering factors such as conjugated linkage types, building blocks, and electron donor-acceptor structures, highly reactive and stable organic semiconductor photocatalysts can be developed.