In this review, we focus on the field of organic photovoltaic cells based on small molecular weight materials. In particular, we discuss the physical processes that lead to photocurrent generation in organic solar cells, as well as the various architectures employed to optimize device performance. These include the donor-acceptor heterojunction for efficient exciton dissociation, the exciton blocking layer, the mixed or bulk heterojunction, and the stacked or tandem cell. We show how the choice of materials with known energy levels and absorption spectra affect device performance, particularly the open-circuit voltage and short-circuit current density. We also discuss the typical materials and growth techniques used to fabricate devices, as well as the issue of device stability, all of which are critical for the commercialization of low-cost and high-performance organic solar cells.

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Replacing toxic solvents with nonhazardous solvents is one of the key challenges for industrial scale commercialization of thin film perovskite photovoltaics. Here, nonhazardous solvent/alcohol/acid systems are presented for the single‐step deposition of pinhole‐free perovskite layers with combined lead halide precursors of Pb(CH3CO2)2·3H2O, PbCl2, and CH3NH3I. Comparable performance to standard hazardous inks is achieved: devices with 15.1% power conversion efficiency are demonstrated and maintain 13.5% tracked for 5 min at maximum power point. Blade coated 4 cm2 solar modules fabricated with highest performing device ink attain 11.9% in power conversion efficiency.