A series of polymers containing benzo[1,2‐b:4,5‐b′]dithiophene and N‐alkylthieno[3,4‐c]pyrrole‐4,6‐dione are designed. By incorporating different alkylthienyl side chains, the fill factor (FF) and open circuit voltage (Voc) of the copolymers are further improved. The experimental results and theoretical calculations show that the size and topology of the side chains can influence the polymer solubility, energy levels, and intermolecular packing by altering the molecular coplanarity. As a result of improved morphology and fine‐tuned energy levels, an increased FF and a high Voc of 1.00 V are achieved, as well as a power conversion efficiency of 6.17%, which is the highest efficiency ever reported for polymer solar cells with a Voc over 1 V.

Solution‐processed hybrid solar cells employing a low band‐gap polymer and PbSxSe1‐x alloy nanocrystals, achieving a record high PCE of 5.50% and an optimal FF of 67% are presented. The remarkable device efficiency can be attributed to the high‐performance active materials, the optimal polymer/NCs ratio and, more importantly, the vertical donor/(donor:acceptor)/acceptor structure which benefits charge dissociation and transport.

The introduction of “double aromatic side‐chains” to the existing polymer backbone is an effective approach to obtain high performance polymer solar cells with low fullerene and additive concentrations, leading to improved absorbance for thin film and more environment‐friendly processing.

A new approach to synthesize self‐doped colloidal Cu3−xP NCs with controlled size and localized surface plasmon resonance absorption is reported. These Cu3−xP NCs show ultrafast exciton dynamics and huge optical nonlinearities due to plasmonic resonances, which afford the first demonstration of plasmonic Cu3−xP NCs as simple, effective, and solution‐processed nonlinear absorbers for high‐energy Q‐switched fiber laser.

By the introduction of different building blocks and side‐chains, a series of donor–acceptor type polymer acceptors containing naphthalene diimide have been successfully prepared. The theoretical and experimental results show that the molecular design effectively tunes the energy levels, solubility, and coplanarity of the acceptor polymers. The intermolecular packing, which has been considered as a key factor in the bulk heterojunction morphology, has been adjusted by changing the coplanarity. As a result of improved morphology and fine‐tuned energy levels, a power conversion efficiency of 6.0% has been demonstrated for the optimized devices, which is among the highest‐efficiencies for reported all‐polymer solar cells. The improved device performance may be attributed to the resemble crystallinity of the donor/acceptor polymers, which can lead to the optimal phase separation morphology balancing both charge transfer and transport.