Recent Advances in Green-Solvent-Processable Organic Photovoltaics

Over the last four years, tremendous progress has occurred in the field of organic photovoltaics (OPVs) and the champion power conversion efficiency (PCE) under AM1.5G conditions, as certified by the National Renewable Energy Laboratory (NREL), is currently 18.2%. However, these champion state-of-the-art devices were fabricated at lab-scale using highly toxic halogenated solvents which are harmful to human health and to the environment. The transition of OPVs from the lab to large-scale production and commercialization requires the transition from halogenated-solvent-processing to green-solvent-processing without compromising the device’s performance. This review focuses on the most recent research efforts, performed since the year 2018 onwards, in the development of green-solvent-processable OPVs and discusses the three main strategies that are being pursued to achieve the proposed goal, namely, (i) molecular engineering of novel donors and acceptors, (ii) solvent selection, and (iii) nanoparticle ink technology.

Visualizing Material Processing via Photoexcitation-Controlled Organic-Phase Aggregation-Induced Emission

Aggregation-induced emission (AIE) has been much employed for visualizing material aggregation and self-assembly. However, water is generally required for the preparation of the AIE aggregates, the operation of which limits numerous material processing behaviors. Employing hexathiobenzene-based small molecules, monopolymers, and block copolymers as different material prototypes, we herein achieve AIE in pure organic phases by applying a nonequilibrium strategy, photoexcitation-controlled aggregation. This strategy enabled a dynamic change of molecular conformation rather than chemical structure upon irradiation, leading to a continuous aggregation-dependent luminescent enhancement (up to ~200-fold increase of the luminescent quantum yield) in organic solvents. Accompanied by the materialization of the nonequilibrium strategy, photoconvertible self-assemblies with a steady-state characteristic can be achieved upon organic solvent processing. The visual monitoring with the luminescence change covered the whole solution-to-film transition, as well as the in situ photoprocessing of the solid-state materials.

Self-Powered All-Inorganic Perovskite Photodetectors with Fast Response Speed

In this manuscript, the inorganic perovskite CsPbI2Br and CsPbIBr2 are investigated as photoactive materials that offer higher stability than the organometal trihalide perovskite materials. The fabrication methods allow anti-solvent processing the CsPbIxBr3−x films, overcoming the poor film quality that always occur in a single-step solution process. The introduced diethyl ether in spin-coating process is demonstrated to be successful, and the effects of the anti-solvent on film quality are studied. The devices fabricated using the methods achieve high-performance, self-powered and the stabilized photodetectors show fast response speed. The results illustrate a great potential of all-inorganic CsPbIxBr3−x perovskites in visible photodetection and provide an effective way to achieve high performance devices with self-powered capability.

Achieving Highly Efficient All-Polymer Solar Cells by Green-Solvent-Processing under Ambient Atmosphere

All-polymer solar cells (all-PSCs) exhibiting superior device stability and mechanical robustness have attracted considerable interests. Emerging polymerized small-molecule acceptors (PSMAs) have promoted the progress of all-PSCs exceeding power conversion efficiency...

Self-Powered All-Inorganic Perovskite Photodetectors with Fast Response Speed

In this manuscript, the inorganic perovskite CsPbI2Br and CsPbIBr2 are investigated as photoactive materials that offers higher stability than the organometal trihalide perovskite materials. The fabrication methods allow anti-solvent processing the CsPbIxBr3−x films, overcoming the poor film quality that always occur in a single-step solution process. The introduced diethyl ether in spin-coating process is demonstrated to be successful, and the effects of the anti-solvent on film quality are studied. The devices fabricated using the methods achieve a high-performance, self-powered and stabilized photodetectors with fast response speed. The results illustrate a great potential of all-inorganic CsPbIxBr3−x perovskites in visible photodetection and provide an effective way to achieve high performance devices with self-powered capability.