Highly Sensitive and Broadband Organic Photodetectors with Fast Speed Gain and Large Linear Dynamic Range at Low Forward Bias

Photodetectors with high photoelectronic gain generally require a high negative working voltage and a very low environment temperature. They also exhibit low response speed and narrow linear dynamic range (LDR). Here, an organic photodiode is demonstrated, which shows a large amount of photon to electron multiplication at room temperature with highest external quantum efficiency (EQE) from ultraviolet (UV) to near‐infrared region of 5.02 × 103% (29.55 A W−1) under a very low positive voltage of 1.0 V, accompanied with a fast response speed and a high LDR from 10−7 to 101 mW cm−2. At a relatively high positive bias of 10 V, the EQE is up to 1.59 × 105% (936.05 A W−1). Inversely, no gain is found at negative bias. The gain behavior is exactly similar to a bipolar phototransistor, which is attributed to the photoinduced release of accumulated carriers. The devices at a low voltage exhibit a normalized detectivity (D*) over 1014 Jones by actual measurements, which is about two or three order of magnitudes higher than that of the highest existing photodetectors. These pave a new way for realization of high sensitive detectors with fast response toward the single photon detection. Organic photodetectors exhibit high photocurrent gain as well as fast response speed and large linear dynamic range at low positive voltage. The results are very similar to a bipolar phototransistor behavior. A normalized detectivity (D*) is over 1014 Jones by actual measurements, which is about two or three order of magnitudes higher than that of the highest existing photodetectors.