1,4-Dihydropyrrolo[3,2-b]pyrroles as a single component photoactive layer: A new paradigm for broadband detection

Single component organic photodetectors capable of broadband light sensing represent a paradigm shift for designing flexible and inexpensive optoelectronic devices. The present study demonstrates the application of a new quadrupolar 1,4-dihydropyrrolo[3,2-b]pyrrole derivative with spectral sensitivity across 350-830 nm as a potential broadband organic photodetector (OPD) material. The amphoteric redox characteristics evinced from the electrochemical studies are exploited to conceptualize a single component OPD with ITO and Al as active electrodes. The photodiode showed impressive broadband photoresponse to monochromatic light sources of 365, 470, 525, 589, 623, and 830 nm. Current density-voltage (J-V) and transient photoresponse studies showed stable and reproducible performance under continuous on/off modulations. The devices operating in reverse bias at 6 V displayed broad spectral responsivity (R) and very good detectivity (D*) peaking a maximum 0.9 mA W^-1 and 1.9 × 10^10 Jones (at 623 nm and 500 μW cm^-2) with a fast rise and decay times of 75 and 140 ms, respectively. Low dark current densities ranging from 1.8 × 10^-10 Acm^-2 at 1 V to 7.2 × 10^-9 A cm^-2 at 6 V renders an operating range to amplify the photocurrent signal, spectral responsivity, and detectivity. Interestingly, the fabricated OPDs display a self-operational mode which is rarely reported for single component organic systems.