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Over the past few decades, organic solar cells (OSCs) have made a significant progress, showing their great potential for low-cost, flexible, lightweight, portable and large-area energy-harvesting devices. In recent years, nonfullerene acceptors have emerged as a new candidate of n-type materials to overcome the disadvantages of fullerene derivatives in tuning optical and electronic properties. The strong and easily adjustable absorption characteristics of nonfullerene acceptors have been considered as a strong point compared to fullerene-type structures, showing a photovoltaic efficiency over ~19%. To further optimize the OSCs for next generation green energy sources, several important points need to be considered carefully. Here we discuss the fundamental correlations between molecular structure, exciton diffusion length, film morphology and device performance in new nonfullerene acceptor-based OSCs. In addition, perovskite solar cells (PeSCs) have also attracted extensive attention because of their inherent advantages such as solution processability, band-gap tunability, high absorption coefficient, and long carrier diffusion length. It has been successfully demonstrated that their power conversion efficiencies exceed 25%, which becomes similar with the highest PCE for crystalline Si solar cells. For PeSCs applications, appropriate charge transport layers (CTLs) are crucial for device performance and stability. The CTLs should have suitable energy levels for effective charge injection/transport while blocking opposite charges. Moreover, the CTL below the perovskite layer is critical because it significantly affects the crystal growth of the perovskite layer and its interfacial defects. In this presentation, a new series of conjugated polyelectrolytes is reported as an ideal interfacial layer and CTLs in PeSCs.
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