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

Abstract

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 × 10 % (29.55 A W ) under a very low positive voltage of 1.0 V, accompanied with a fast response speed and a high LDR from 10 to 10 mW cm . At a relatively high positive bias of 10 V, the EQE is up to 1.59 × 10 % (936.05 A W ). 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 10 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.

Light Detection in Open‐Circuit Voltage Mode of Organic Photodetectors

“…Figure a displays the V oc response to a 50 ms light pulse with an incident power density of 25.1 µW cm −2 at 536 nm. The photodetector exhibits a V oc of 296 mV with a rise time t r of 1.8 ms and a V oc fall time t f of 2.2 ms. For comparison, the photocurrent response times are typically in the ≈µs range for organic and perovskite photodetectors operating in current mode, and in the ≈ms range for photomultiplication type organic photodetectors . One must note here that photovoltage and photocurrent responses differ in their nature.…”

Recent Progress on Photomultiplication Type Organic Photodetectors

“…Recently, Deng and Xu et al. co‐reported PM type OPDs with vertical structure of ITO/poly{2,6′‐4,8‐di(5‐ethylhexylthienyl)benzo[1,2‐b;3,4‐b]dithiophene‐alt‐5‐dibutyloctyl‐3,6‐bis(5‐bromothiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4‐dione} (PBDTT‐DPP):PC 71 BM(1:2, wt/wt)/ MoO 3 /Al, exhibiting broad spectral response range of 350–900 nm . The working mechanism of PM effect can be attributed to the photo‐induced release of accumulated carriers in MoO 3 layer under forward bias, in which MoO 3 interfacial layer works as a photon‐controllable “valve.”…”

“…The response speed of most PM type OPDs were characterized by rise/delay time. The −3 dB bandwidth of these PM type OPDs can be estimated according to the Equation: , where τ is the response time of device. For better comparing the EQE (gain)–bandwidth compromise of photodetectors, the plots of EQE versus bandwidth of PM type OPDs, colloidal quantum dot (CQD) photodetectors, and perovskite photodetectors are exhibited in Figure .…”

Multifunctional Optoelectronic Device Based on Resistive Switching Effects

“…In the optoelectronic memristor ( Figure 3), both optical and electrical signals are able to modulate the resistance states of a "memory" layer, which is sensitive to both electrical and optical signals. Therefore, photosensitive semiconductor materials will meet the demands of the "memory" layer, such as silicon, cerium oxide, zinc oxide, perovskite, low-dimensional materials and organic materials, and so on [47][48][49][50][51][52].…”

“…Optoelectronic memristor-based neuromorphic devices, integrating the functions of information storage, processing, image detection, and memory together, may provide high potential for intelligent image sensor and optoelectronic in-memory computation. Based on the integrated photonics [1][2][3][4][5][6][7][8][9][10], optoelectronics [47][48][49][50][51][52][53][54][55][56][57][58][59][60], and optogenetics [98][99][100], an optoelectronic artificial neural network may play a key role in future human-machine interactive devices.…”