High-Performance organic photodiodes for Blue-Light hazard detection

In this study we incorporated a PffBT4T-2OD:PC₇₁BM bulk-heterojunction (BHJ) active layer in the layer structure ITO/ZnO/BHJ/MoO₃/Ag, obtaining high-performance organic photodiodes (OPDs) for application in blue-light hazard (BLH) detection. The high crystallinity of PffBT4T-2OD resulted in the OPD displaying high performance even when the thickness of the BHJ layer was up to 850 nm. The efficient OPD suppressed charge injection (from the metal contacts), thereby providing state-of-the-art performance: external quantum efficiencies of greater than 70% (380–710 nm), a value of J_d of 1.18 × 10^-9 A cm⁻² (-2 V), and high detectivity [2.9 × 10¹³ Jones, −2 V (710 nm)]. The observed ultra-high cut-off frequency [greater than800 kHz (at 530 nm), with rise/fall times of less than 350 ns at reverse biases of less than −3 V] exceeded that of a silicon photodiode and made the system suitable for use in image photosensors and medical monitoring. The wide linear dynamic range (LDR, 530 nm) of the OPD (139 dB at −1 V, from 2.2 × 10^-4 to 2.5 × 10^-11 A cm⁻²) encompassed the mesopic and scotopic vision regimes. Combined with the design of a BLH filter, we calculated the environmental BLH weighted irradiation power density [WD_BLH = C_B × J_SC (current density of diode)] to evaluate the BLH effect for various light sources and commercially available lenses; here C_B (12.69, reported herein) is a corrective constant for BLH photodetectors. Finally, our design allowed ready determination of the ratio of blue-violet and blue-green light.