We design the experiments to understand interrelationships between morphology and performance parameters.
FF increases with the increased P3HT phase purity and the decreased PCBM aggregate thickness.
VOC increases with the decrease of P3HT conjugate length.
JSC relates to the interfacial region area and the phase purity of P3HT.
The devices having large PCBM crystals can obtain good PCE if they have enough interfacial areas.