Transient analysis of photomultiplication-type organic photodiodes

Abstract

Photomultiplication-type organic photodetectors have emerged as a class of next generation solution-processed photodetectors with high gain. Despite this promising feature, the reported photodectors still suffer from relatively large dark currents at high bias voltages. To overcome this drawback, a mechanistic understanding of the photomultiplication effect in organic photodiodes is required. In this work, we advanced the performance of photomultiplication-type organic photodetectors by tuning the active layer composition and interfacial layers. The optimized devices exhibit small dark currents and flat dark current–voltage curves under the reverse bias condition up to −10 V. The optimized photodetectors also reached an ultra-high responsivity of 23.6 A/W and the specific detectivity of 1.04 × 1012 Jones at −10 V. More importantly, we investigated the photomultiplication process with multiple transient techniques and revealed that the photoconductive gain effect is a slow process, which relies on the photo-Schottky effect enabled by charge carrier tunneling and the accumulation of holes. Furthermore, we also demonstrated prototypical pulsed-light detection based on the optimized devices, which showed great potential for real applications.

Van der Waals Black Phosphorus/Bi10O6S9 Heterojunction Harvesting Ambient Electric Field Energy for Enhanced Photoelectrochemical Sense

“…This is because BP nanosheets are cladded on the Bi 10 O 6 S 9 film, have more active sites to be in contact with more Bi 10 O 6 S 9 , and form a van der Waals effect with Bi 10 O 6 S 9, as shown in Figures b and . The current densities of WB and WBB electrodes further increase slowly, which may be attributed to the trapping of electrons or holes by defects in the electrode or the electrostatic gain that the applied bias causes holes entering the electrode from the external circuit …”

“…The current densities of WB and WBB electrodes further increase slowly, which may be attributed to the trapping of electrons or holes by defects in the electrode or the electrostatic gain that the applied bias causes holes entering the electrode from the external circuit. 92 The EIS spectra of Bi 10 O 6 S 9 , WO 3 , WB, and WBB electrodes are measured to investigate the internal interfaces and are shown in Figure 6d. The corresponding equivalent circuit model is shown in the plug-in.…”

Morphological Effects on the Performance of Broadband Organic Photomultiplication Photodetectors Containing Selenium Substituted Non‐Fullerene Acceptors

“…Because PM effects involve charge trapping and subsequent charge tunneling injection from the electrodes, these processes collectively slowed down the frequency response of PM-OPDs. [37] The noise spectral density was measured at 0, −0.2, and −1 V biases, respectively (Figure 4b). The total noise (I n ) was frequency dependent below 10 Hz and apparently dominated by the 1/f flicker noise.…”

Dual-Band, Efficient Self-Powered Organic Photodetectors with Isotype Subphthalocyanine-Based Heterojunctions toward Secure Optical Communications

“…Then, we investigated the electrically active traps (or defects) close to the heterojunction interface in the device by DLTS measurements. DLTS can effectively probe the energy level position ( E t ), capture cross section (σ), and trap concentration ( N t ) by filling charge carriers to the trap states within the space charge region at a forward bias and extracting the trapped carriers at a reverse bias. , …”

“…DLTS can effectively probe the energy level position (E t ), capture cross section (σ), and trap concentration (N t ) by filling charge carriers to the trap states within the space charge region at a forward bias and extracting the trapped carriers at a reverse bias. 58,59 The devices were initially set under a small reverse bias of −0.2 V. The forward filling bias voltage was set at 0.5 V with a pulse width of 10 ms. Four devices were scanned by DLTS from 130 to 350 K. In such conditions, all DLTS signals exhibit positive peaks, as showcased in Figure 6c, which is related to the majority carrier (electron) traps. 59 From the Arrhenius plots in Figure 6d, the trap densities for control devices, devices 1, 2, and 3, were estimated at about 4.7 × 10 14 , 9.6 × 10 13 , 8.1 × 10 13 , and 7.6 × 10 13 cm −3 , respectively, from the signal intensities and carrier concentrations under the measurement bias voltages.…”