In the pursuit of high power conversion efficiency (PCE) for organic photovoltaics (OPVs), we synthesized four stereoisomeric 2,2′-((2Z,2′Z)-((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl)bis(methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDIC) type small-molecule acceptors that combine the indaceno[1,2-b:5,6-b′]dithiophene (IDT) core with two different electron deficient (3-oxo-2,3-dihydro-1H-indene-2,1-diylidene) dimalononitrile peripheral end groups, with hexyl or hexyloxyl side chains, namely cis-ID-OR, trans-ID-OR, cis-ID-OR-4Cl, and trans-ID-OR-4Cl, respectively, as the third component for being incorporated into the PM6:Y6 active layer for the fabrication of OPVs. The PM6 : Y6 : cis-stereoisomer—cis-ID-OR or cis-ID-OR-4Cl—(1 : 1 : 0.2 wt ratio) ternary blend that incorporates the cis-stereoisomer with either hexyl or hexyloxyl side chains oriented in the same direction imparted a larger crystalline correlation length (CCL), as compared to that in the cases of the trans-stereoisomer—trans-ID-OR or trans-ID-OR-4Cl—with hexyl or hexyloxyl side chains oriented in opposite directions, with the PM6:Y6:cis-ID-OR ternary blend providing the largest CCL of 25.8 Å, which facilitates carrier transport in the system. As a result, the PM6 : Y6 : cis-ID-OR (1 : 1 : 0.2 wt ratio) device displays the highest short-circuit current density (J_sc) value of 25.4 mA cm⁻², and an improved PCE value of 17.1%, over 15.8% for the device with the PM6:Y6 active layer (J_sc = 23.8 mA cm⁻², CCL = 19.8 Å), whereas the PCE value of PM6 : Y6 : trans-ID-OR (1 : 1 : 0.2 wt ratio) only reached 14.7%. The enhancement in the PM6:Y6:cis-ID-OR device results from the higher J_sc and fill factor values that were affected by CCL values. Therefore, this approach of using the side-chain orientation of the chiral-isomer acceptor to induce variations in CCL values can provide the enhancement of the PCE values of the devices when incorporating the cis-stereoisomer rather than the trans-stereoisomer.