Photocurrent Amplification in Bulk Heterojunction Organic Phototransistors with Different Donor–Acceptor Ratio

Abstract

In this paper, the amplification of the photocurrent in organic phototransistors (OPTs) employing bulk heterojunctions (BHJs) with different donor–acceptor ratios has been studied. As a model system, poly[2‐methoxy‐5‐(3’,7’‐dimethyloctyloxy)‐p‐phenylene vinylene] (OC1C10‐PPV) and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) are used as donor and acceptor, respectively, combined with Al contact. It is found that for OPTs the mobility of the majority carrier is the dominating factor for maximizing the photocurrent. This is different from organic photodiodes (OPDs) where balanced hole and electron mobilities are important. For OPDs using the same model system, the maximum photocurrent is obtained for a PCBM content of 80 wt.% while for OPTs, it retained its photocurrent from PCBM 80 wt.% up to PCBM 100 wt.%. In addition, BHJ transistors respond more rapidly to changes in the illumination intensity than transistors with a pure PCBM layer.

Suppressing Dark Current in Organic Phototransistors through Modulating Electron Injection via a Deep Work Function Electrode

“…The time for the photocurrent to reach 90% of the ON current was <30 ms. For the OFF state of the OPTs, the same saturation rate was observed. These response time characteristics are on the same magnitude as those of previously reported OPTs with similar structures …”

“…The light current was measured at V gs = 15 V and determined to be 1 × 10 –7 A. The responsivity was >5.9 × 10 –3 A W –1 under illumination with a power density of 42 mW cm –2 , which is consistent with OPTs with similar structure. , …”

“…The responsivity was >5.9 × 10 −3 A W −1 under illumination with a power density of 42 mW cm −2 , which is consistent with OPTs with similar structure. 22,23 The gate voltage dependence on responsivity and photosensitivity is plotted in Figure 3a,b. Both OPTs with and without MoO x showed similar responsivity while their photosensitivity differs.…”

Tunable Photoelectric Properties of n‐Type Semiconducting Polymer:Small Molecule Blends for Red Light Sensing Phototransistors

“…Fullerene derivatives are dominantly selected as the electron acceptors, while many electron donors are available for photodetection layer assembling. [28][29][30][31][32][33][34][35][36][37] However, the fullerenes suffer from insufficient red light absorption, due to their wide Semiconducting blend heterostructures, composed of conjugated polymer with photoresponsive organic crystals, provide an effective way to achieve promising photodetection devices. Here, solution-processed n-type N2200 conjugated polymer and quinoidal thienoisoindigo (TIIQ) small molecule blend is used to construct phototransistors for red light detection.…”

“…Fullerene derivatives are dominantly selected as the electron acceptors, while many electron donors are available for photodetection layer assembling. [ 28–37 ] However, the fullerenes suffer from insufficient red light absorption, due to their wide bandgap and morphological instability. [ 38,39 ] Nam et al.…”