Achieving spectrally selective organic photodetectors (OPDs) without using broadband-absorbing semiconductors with input filtering has been a strenuous challenge. Charge collection narrowing (CCN) is a promising strategy to obtain spectrally selective near-infrared (NIR) OPD by adopting a thick bulk heterojunction (BHJ) as active layers. In this work, a random terpolymer comprised from a diketopyrrolopyrrole (DPP), thiophene (T) and benzothiadiazole (BT), ranDPP-2TBT, was prepared and used as a donor material in combination with the low band gap non-fullerene acceptor (NFA) IEICO-4F. OPDs with a low dark current density (6.88 × 10-9 A cm-2) and a 68 nm full-width-at-half-maximum (FWHM) narrowband response (R = 0.13 A W-1 at 916 nm) in the NIR were achieved. Finally, an application of the OPD as a biometric heart-rate sensor via photoplethysmography (PPG) for real-time monitoring is demonstrated.