Light Detection in Open‐Circuit Voltage Mode of Organic Photodetectors

Abstract

Organic photodetectors (OPDs) are promising candidates for next‐generation light sensors as they combine unique material properties with high‐level performance in converting photons into electrical signals. However, low‐level light detection with OPD is often limited by device dark current. Here, the open‐circuit voltage (Voc ) regime of OPDs is shown to be efficient for detecting low light signals (<100 µW cm−2). It is established that the light‐dependence of Voc exhibits two distinct regimes as function of irradiance: linear and logarithmic. Whereas the observed logarithmic regime is well understood in organic photovoltaic cells (OPVs), it is shown experimentally and theoretically that the linear regime is due to the non‐infinite shunt resistance of the OPD device. Overall, OPDs composed of rubrene and fullerene show photovoltage light sensitivity across nine orders of magnitude with a detection limit as low as 400 pW cm−2. A photovoltage responsivity of 1.75 V m2 W−1 demonstrates highly efficient performance without the necessity to supress high dark current. This approach opens up new possibilities for resolving low light signals and provides simplified design rules for OPDs.

Multifunctional Diode Operation of Tetracene Sensitized Polymer:Fullerene Heterojunctions with Simultaneous Electroluminescence in Visible and NIR Bands

“…Previously, we have shown that rubrene can efficiently function as an OPV and OLED with sub-bandgap turn-on voltage and able to detect ultralow light signals when combined with a suitable acceptor, such as fullerene-C 60 . [13,14,15] The origin of the multifunctional diode response of these chromophores has now been linked to arise due to the delicate interplay between singlet excitons, charge transfer states and triplet excitons. [16,17,18] This has led to research into a new class of organic optoelectronic devices, as opposed to their complete reliance on singlet excitons where the formation of triplet excitons has traditionally…”

Highly Sensitive and Ultrafast Organic Phototransistor Based on Rubrene Single Crystals

“…Organic materials have attracted tremendous attention due to various advantages such as their low manufacturing costs, low-temperature processability, intrinsic mechanical flexibility, and diversified band gap selection through molecular design. , Organic single crystals present highly ordered molecular packing, absence of grain boundaries, and extremely low defect density, which make them an ideal platform for both the fundamental research and potential applications. Rubrene is a typical organic semiconductor with a herringbone packing arrangement and has been widely exploited in high-performance field-effect transistors, , flexible strain sensors, and phototransistor memories, , due to its high carrier mobility, intrinsic mechanical flexibility, and excellent absorption .…”

Efficient p‐Doping with F6TCNNQ for Improving Performance of Polymer Photodetectors with Photomultiplication

“…The rise time (t r ) and fall time (t f ) of transient photocurrent are defined as the time for photocurrent raising from 10% to 90% of the maximum photocurrent and the time for photocurrent decreasing from 90% to 10% of the maximum photocurrent. [36] The t r and t f of PM-PPDs with F 6 TCNNQ in active layers are estimated to be 16.3 and 56.7 ms, respectively, which are shorter than the corresponding values of 27.7 and 85 ms for PM-PPDs without F 6 TCNNQ in active layers. The increased response speed of PM-PPDs with F 6 TCNNQ in active layers should be due to the enhanced hole mobility.…”