Photovoltaic and photoconductivity effect in thin-film phototransistors based on a heterocyclic spiro-type molecule

Abstract

We reported on photovoltaic and photoconductivity effects as the underlying mechanism in thin-film phototransistors based on 2,2′,6,6′-Tetraphenyl-4,4′-spirobi[cyclopenta[2,1-b;3,4-b′]dithiophene]. The responsivity and the ratio of photocurrent to dark current were 25 A/W and 290, respectively. Our devices also exhibited a field-effect mobility of (1−2)×10−4 cm2∕V s and an ON/OFF ratio of ∼103. Hysteresis in the transfer curve was observed after the curves were measured from the ON-state to the OFF-state and vice versa. In this case, the gate voltage (at drain bias −20 V and drain current −1 nA) shifted by 8 V at an optical power of ∼20 μW.

Device physics of highly sensitive thin film polyfluorene copolymer organic phototransistors

“…We include it here for comparison as it has been used to successfully fit the results for other phototransistors. 11,31 As it can also fit the results here, it does suggest some physical basis for a logarithmic relationship between photocurrent and light intensity in organic phototransistors.…”

Electrical transport and persistent photoconductivity in monolayer MoS2phototransistors

“…[12,34] for similar devices, but is lower than the ones achieved in more recent works, with the devices treated or measured under special conditions [11,15]. In general, two different effects are assumed to occur in field effect phototransistors under illumination depending on the applied voltage : The photogating (PG, often called photovoltaic) effect and the photoconductive (PC) effect [35][36]. Hence, the photocurrent is the sum of two contributions:…”

“…The photoconductive effect refers to the increase in conductivity, ∆ , due to photogeneration of electron-hole pairs in the channel, and is less dependent on the gate voltage [35,37]. Its contribution to the photocurrent is expressed as…”

Illumination and dipole layer effects on the density of state distribution in n-type organic thin film phototransistors based on naphthalene bis-benzimidazole: Experiment and modeling

“…Therefore, the channel conductance which consists of both hole and electron charge carriers, as well as the drain current, is increased in proportional to illumination intensity [43,46]. In order to more explain the photoinduced response, the photovoltaic and photoconductive effects have to be evaluated under illumination [47][48][49][50][51]. A photovoltaic effect can be observed when photoTFTs operates at the on-state where the drain photocurrent (I D,photo on-state) dominated by the photovoltaic effect.…”