The present work documents the synthesis of a new and highly energetic indandione based D-p-A planar molecule, 2-(5.-hexyl-[2,2':5'2 '' terthiophen]-5-yl) methylene)-1H- indene-1,3(2H) dione, H3T-ID), as donor material for bulk-heterojunction organic solar cells (BJH-OSCs). The photophysical properties, optoelectrical characterization and microscopic images were thoroughly studied. H3T-ID exhibited good absorption behavior with maximum absorbance at similar to 495 nm and displayed the optical band gap of similar to 1.98 eV. The existence of pspacer and hexyl side chain in H3T-ID significantly improved the thin film morphology, molecular packing and enhanced the charge transport. H3T-ID organic molecule acquired well-matched HOMO and bountifully higher LUMO energy levels w.r.t. PC61BM acceptor. The photovoltaic characteristics of the fabricated BHJ-OSC using H3T-ID as donor and PC61BM as acceptor displayed maximum PCE = similar to 4.05%, good JSC = similar to 10.43 mAcm(-2), V-OC = similar to 0.77 V and FF = 0.51. The stability test revealed that the fabricated BHJ-OSCs showed good reproducibility and stability by retaining over similar to 80% of its initial PCE for 15 days without encapsulation.