Organic solar cells (OSC) offer great potential in lowering material and production costs for the proliferation of photovoltaics. However, OSC generally suffer from low efficiencies to meet commercial application standards. In Yale TMD lab, we realize the first highly efficient quaternary blend solar cells that break efficiency above 10% – by blending complementary squaraine small molecules and polymer (multi-donor) in the active layer. Compared to the conventional binary architectures, our quaternary systems are enhanced both optically and electronically by energy transfer mechanism and co-crystallinity morphology with PTB7 copolymer as the host material. Furthermore, the same strategy achieves great success in improving the performances of both PT8 (a high open circuit voltage compound) and PTB7-Th (a high current density polymer) systems. In summary, we demonstrate that our multi-donor systems possess significant advantages in (i) widening light absorption window, (ii) improving surface and active layer morphology, (iii) promoting co-crystallization and denser packing structures, (iv) inducing multiple energy and charge transfer pathways to reduce recombination, and (v) enhancing charge mobility. Our findings also indicate that such approach can be utilized to increase the efficiency of complex OSC systems, as well as perovskite solar cells for future applications.