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Sequential deposition of the active layer in organic solar cells (OSCs) is favorable to circumvent the existing drawbacks associated with controlling the microstructure in bulk‐heterojunction (BHJ) device fabrication. However, how the processing solvents impact on the morphology during sequential deposition processes is still poorly understood. Herein, high‐efficiency OSCs are fabricated by a sequential blade coating (SBC) through optimization of the morphology evolution process induced by processing solvents. It is demonstrated that the device performance is highly dependent on the processing solvent of the upper layer. In situ morphology characterizations reveal that an obvious liquid–solid phase separation can be identified during the chlorobenzene processing of the D18 layer, corresponding to larger phase separation. During chloroform (CF) processing of the D18 layer, a proper aggregation rate of Y6 and favorable intermixing of lower and upper layers results in the enhanced crystallinity of the acceptor. This facilitates efficient exciton dissociation and charge transport with an inhibited charge recombination in the D18/CF‐based devices, contributing to a superior performance of 17.23%. These results highlight the importance of the processing solvent for the upper layer in the SBC strategy and suggest the great potential of achieving optimized morphology and high‐efficiency OSCs using the SBC strategy.

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Copper-doped lanthanum phosphate (LaPO 4 :Cu) nanocomposites were successfully synthesized using hydrothermal processes for potential application in solar energy harvesting via thin film organic solar cells. LaPO 4 :Cu is attracting interest in application for photovoltaic because of its stability and broad absorption band in the visible spectrum. The structure and morphological properties of the synthesized nanocomposite were studied using high-resolution tunneling and scanning electron microscopy. The solar absorber layer of the solar cells under investigation was composed of a mixture of poly-3hexylthiophene(P3HT) and (6-6) phenyl-C61-butyric acid methyl ester (PC 61 BM) at a 1:1 ratio by weight. The absorber layers are then mixed with LaPO 4 :Cu nanocomposites at different concentrations. The inverted device architecture is employed in this investigation, which is composed of different layers of materials as follows: glass/ITO/ZnO/ P3HT:PC 61 BM: LaPO 4 :Cu/MoO 3 /AL. The results showed that an improved power conversion efficiency (PCE) was observed from all devices containing the nanocomposite. The PCE has increased from 3.58% to a maximum of 6.11% due to the incorporation of the LaPO 4 :Cu nanocomposite. The changes in device performance were attributed to the enhanced optical absorption by virtue of light scattering processes and localized surface plasmon resonance in the photoactive medium. Moreover, the LaPO 4 :Cu nanocomposite-doped inverted solar cells were found to be very stable under an ambient environment.