Bulk- and layer-heterojunction phototransistors based on poly [2-methoxy-5-(2′-ethylhexyloxy-p-phenylenevinylene)] and PbS quantum dot hybrids

Abstract

The responsivity (R) of a thin film photodetector is proportional to the product of its photo-induced carrier density (n) and mobility (μ). However, when choosing between layer heterojunction (LH) and bulk heterojunction (BH) field-effect phototransistors (FEpTs), it is still unclear which of the two device structures is more conducive to photodetection. A comparison study is performed on the two structures based on polymer and PbS quantum dot hybrids. Both devices exhibit ambipolar behavior, with μE ≈ μH = 3.7 cm2 V−1 s−1 for BH-FEpTs and μH = 36 cm2 V−1 s−1 and μE = 52 cm2 V−1 s−1 for LH-FEpTs. Because of the improvements in μ and the channel order degree (α), the responsivity of LH-FEpTs is as high as 101 A/W, which is as much as two orders of magnitude higher than that of BH-FEpTs (10−1A/W) under the same conditions. Although the large area of the BH improves both the exciton separation degree (β) and n in the BH-FEpT, the lack of an effective transport mechanism becomes the main constraint on high device responsivity. Therefore, LH-FEpTs are better candidates for use as photo detectors, and a “three-high” principle of high α, β, and μ is found to be required for high responsivity.

Visible‐Light Ultrasensitive Solution‐Prepared Layered Organic–Inorganic Hybrid Perovskite Field‐Effect Transistor

“…Commonly, the three‐terminal configuration of field‐effect transistors (FETs), compared to the two‐terminal device, can improve the performance of the photodetector by reducing noise and amplifying the electrical signal. Incorporating organic semiconductors and their hybrids into FETs has been proved to be a feasible way to convert incident photons into electrical signals …”

Enhanced near-infrared photoresponse of organic phototransistors based on single-component donor–acceptor conjugated polymer nanowires

“…Such devices can be used to fabricate high-performance polymer phototransistors. [17][18][19][20][21] Phototransistors based on poly(3-hexylthiophene) (P3HT)/PbS QDs and poly(N-alkyl diketopyrrolo-pyrroledithienylthieno[3,2-b] thiophene) (DPP-DTT)/ [6,6]-phenyl-C61-butyric acid methylester (PCBM) hybrid films were explored by Yan's and Zhao's groups, respectively. 18,19 Both of their results demonstrated ultrahigh responsivity under NIR illumination.…”

“…17,20,21 For example, Zhang et al reported bulk-as well as layer-heterojunction phototransistors based on poly[2methoxy-5-(20-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) and PbS QDs with photoresponsivities of 100 mA W −1 and 10 A W −1 , respectively. 17 The NIR OPTs based on a hybrid planar-bulk heterojunction structure of CuPc/PbPc:PTCDA exhibited a photoresponsivity of 322 mA W −1 and a maximal photo-current/dark current ratio of 9.4 × 10 2 . 21 These numbers are much lower than Yan's and Zhao's results.…”

High-Performance Phototransistors Based on PDIF-CN2 Solution-Processed Single Fiber and Multifiber Assembly

“…Organic phototransistors, i.e., OFETs in which an incident light is used in addition to a gate field to modulate the charge-carrier density inside the channel, have many advantages over their inorganic counterparts, such as the tunability of their optoelectronic properties via the molecular design and their possibility to be assembled on nonplanar supports opening perspectives toward their flexible thus wearable applications. − Low-dimensional organic architectures such as crystalline micro/nanowire, − microribbon and quantum dot , structures have showed high photosensitivity and high charge carrier properties. Among organic semiconducting molecules used as active components in efficient phototransistors, perylene di-imide (PDI) derivatives are particularly suitable because of their characteristic absorption in the visible region combined with the capacity to transport electrons. − One of the major limitations of organic transistors, especially those based on n -type systems, is their air sensitivity.…”