Organic Ternary Bulk Heterojunction Broadband Photodetectors Based on Nonfullerene Acceptors with a Spectral Response Range from 200 to 1050 nm

Abstract

Compared with the electron donor of the bulk heterojunction (BHJ) organic/inorganic photodetectors (OPDs), there is less development in the field of electron acceptors that have strong absorption capacity in the visible light and near-infrared (NIR) region, which hinders the further research and development of OPDs. As a traditional acceptor, fullerene has limited electronic tunability and weak visible light absorption, which limits the optical absorption and electron tunability properties required by the donor. In this work, a novel low-band-gap nonfullerene acceptor (NFA) sodium indocyanine green (Ir-125) is introduced, blended with a fullerene derivative acceptor [6,6]-phenyl C61-butyric acid methyl ester (PC61BM) and a conjugate polymer donor poly(3-hexylthiophene) (P3HT), to form ternary BHJ-active layers, forming a high-performance BHJ OPD with ultrawide spectral response from the ultraviolet (200 nm) to visible light to NIR (1050 nm) region. Here, the high-performance OPD exhibits complementary absorption on the scale of exciton diffusion length and is uniformly mixed with the pure phases. The OPD has high external quantum efficiency (132%) and high detectivity (9.07 × 10 12 Jones), which is much higher than those of P3HT:PC61BM, which are 58% and 3.62 × 10 12 Jones, respectively, and also, OPDs show an increase in the photocurrent to dark current ratio (I photo /I dark ) by one order of magnitude. The generation of the balanced photocurrent between the donor and NFA eliminates the undesirable limitation on the donor imposed by fullerene derivatives and expand the response range of the BHJ OPD, which opens up a new avenue toward a higher efficiency and wider response range for the OPDs.

Broadening of the Response Spectrum and Gain in the Optoelectronic Performance of P3HT:PC61BM/ZnO NWs “Embedded” Heterojunction Photodetector

“…Noise equivalent power (NEP) is the minimum optical power required to distinguish optical current from noise current, which represents the characteristics of the lowest detectable light of PDs. The NEP of the PDs can be described as normalN normalE normalP = A D * where A is the active area (8.25 × 10 –4 cm 2 ) in our work. Table summarizes the calculated data of P3HT:PC61BM/ZnO NWs PD and ZnO NWs PD under a 6 V bias, where the illumination intensity was 1 mW/cm 2 .…”

“…22,27 Noise equivalent power (NEP) is the minimum optical power required to distinguish optical current from noise current, which represents the characteristics of the lowest detectable light of PDs. The NEP of the PDs can be described as 30…”