Unsymmetrical Squaraine Dye-Based Organic Photodetector Exhibiting Enhanced Near-Infrared Sensitivity

Abstract

An unsymmetrical squaraine (SQ) derivative containing anthracene and phenyl hydrazine (ANPHSQ) units linked to the central SQ was synthesized and used as electron donors in bulk heterojunction photovoltaic mode organic photodetectors (OPD), containing PCBM as the electron acceptor. Although the ANPHSQ exhibited a strong narrow band in the near infrared peaking at ∼760 nm in solution, the OPD constructed with this dye exhibited a broad spectral response extending to 950 nm. The enhanced sensitivity in the long wavelength region could be attributed to formation of ANPHSQ aggregates within the devices. A photocurrent of 1.3 mA/cm2, almost 3–5 orders of magnitude larger than the dark current (∼50 nA/cm2), was observed in the presence of light at −1 V bias condition. Devices showed an increase in external quantum efficiency from ∼4 to ∼12% as the bias varied from 0 to −1 V. At a reverse bias of −1 V, the device with a ANPHSQ exhibited a maximum shot-noise-limited specific detectivity of 6 × 1011 cm Hz1/2 W–1 (Jones) @ 840 nm with an ultrafast photoresponse in the range of ∼15 ns. The study of relaxation dynamics of the ANPHSQ excited state using femtosecond pump–probe spectroscopy and time-correlated single-photon counting indicated efficient charge transfer between the excited state of ANPHSQ and PCBM.

Synthesis and Nanoarchitectonics of Novel Squaraine Derivatives for Organic Photovoltaic Devices

“…This explains why the LUMO levels for compounds 4b and 5b could not be determined directly from the CV measurements. During the oxidative scan, on the other hand, no change in the color of the films were observed, and the results obtained are appropriate for the determination of the HOMO levels of −5.07, −5.19, and −5.34 eV, for compounds 4b , 5b , and 5c , respectively, and these values are comparable to other small molecule squaraine compounds published so far [ 32 , 33 ]. These values are also supported by the fact that compound 5c displayed complete stability during both the forward and backward scans, and the bandgaps resulting from both methods, the optical and electrochemical, are very similar.…”

Highly Responsive and Thermally Reliable Near‐Infrared Organic Photodiodes Utilizing Naphthalocyanine Molecules Tuned with Axial Ligands

“…[ 7,9 ] Nonetheless, recent efforts have led to significant boosts in the performance of NIR OPDs using either polymers [ 10–13 ] or small molecule materials. [ 14–19 ] For instance, Xiong et al. investigated solution‐processed polymer NIR OPDs with PMDPP3T:PC 61 BM bulk heterojunction (BHJ), exhibiting a low dark current density ( J d ) of 3.0 nA cm −2 at −0.2 V and a high external quantum efficiency (EQE) of 48% at 850 nm (a responsivity of 0.37 A W −1 ) for broad sensing applications.…”

“…[7,9] Nonetheless, recent efforts have led to significant boosts in the performance of NIR OPDs using either polymers [10][11][12][13] or small molecule materials. [14][15][16][17][18][19] For instance, Xiong et al investigated solutionprocessed polymer NIR OPDs with PMDPP3T:PC 61 BM bulk heterojunction (BHJ), exhibiting a low dark current density (J d ) of 3.0 nA cm −2 at −0.2 V and a high external quantum efficiency (EQE) of 48% at 850 nm (a responsivity of 0.37 A W −1 ) for broad sensing applications. [11] A further improvement on the device performance has been recently made by introducing a very thick active layer (≈300 nm) with a non-fullerene acceptor (PTB7-Th:CO1-4Cl), achieving a high EQE of 66% at 960 nm (0.5 A W −1 ), a low J d of 7 nA cm −2 at −2 V, and a detectivity around 10 12 Jones.…”

“…[11] A further improvement on the device performance has been recently made by introducing a very thick active layer (≈300 nm) with a non-fullerene acceptor (PTB7-Th:CO1-4Cl), achieving a high EQE of 66% at 960 nm (0.5 A W −1 ), a low J d of 7 nA cm −2 at −2 V, and a detectivity around 10 12 Jones. [12] On the other hand, small moleculebased OPDs have also shown promising results, particularly featuring selective response to NIR wavelengths, which are mostly based on porphyrin, [14] squaraine, [15] and phthalocyanine (Pc). [16][17][18][19] Among the molecules, Pc-based NIR photodetectors have recently revealed the outstanding device performance.…”

Spotlight on Charge-Transfer Excitons in Crystalline Textured n-Alkyl Anilino Squaraine Thin Films

“…Squaraine dyes are an attractive class of donoracceptor-donor type molecular semiconductors that have been used in a variety of applications. [1][2][3][4][5][6] Since their solid-state absorption and solute-state fluorescence are strong in the visible to near-infrared region, their purposes as p-type material range from solar cells [7][8][9][10][11] and photosensors, [12][13][14][15] even in biological environment, 16 to thin film transistors, 17 as well as photosensitizers in photodynamic therapy 18,19 and fluorescent labels. 20,21 Functionality typically arises from supramolecular interactions giving rise to new phenomena not present on a a) Electronic mail: manuela.schiek@jku.at molecular level.…”