Ultra‐High Alignment of Polymer Semiconductor Blends Enabling Photodetectors with Exceptional Polarization Sensitivity

Abstract

Photodetectors that can sense not only light intensity but also light's polarization state add valuable information that is beneficial in a wide array of applications. Polymer semiconductors are an attractive material system to achieve intrinsic polarization sensitivity due to their anisotropic optoelectronic properties. In this report, the thermomechanical properties of the polymer semiconductors PBnDT‐FTAZ and P(NDI2OD‐T2) are leveraged to realize bulk heterojunction (BHJ) films with record in‐plane alignment. Two polymer blends with distinct weight average molar masses (Mw) are considered and either a strain‐ or rub‐alignment process is applied to align the polymer blend films. Optimized processing yields films with dichroic ratios (DR) of over 11 for the high Mw system and nearly 17 for the low Mw system. Incorporating the aligned films into photodetectors results in a polarized photocurrent ratio of 15.25 with corresponding anisotropy ratio of 0.88 at a wavelength of 530 nm, representing the highest reported photocurrent ratio for photodiodes that can operate in a self‐powered regime. The demonstrated performance showcases the ability of polymer semiconductors to achieve BHJ films with exceptional in‐plane polymer alignment, enabling high performance polarization sensitive photodetectors for incorporation into novel device architectures.

Preparation of oriented poly(lactic acid) thin films by a combination of high temperature rubbing and thermal annealing: Impact of annealing parameters on structure, polymorphism and morphology

“…Of interest are some donor‐acceptor low bandgap polymers such as poly(benzodithiophene‐alt‐dithienyl difluorobenzotriazole) used for instance in polarized photodetectors. [ 43 ]…”

“…Of interest are some donor-acceptor low bandgap polymers such as poly(benzodithiophene-alt-dithienyl difluorobenzotriazole) used for instance in polarized photodetectors. [43] A simple and versatile method combining rubbing and annealing can be used to fabricate smooth polymer films with controlled orientation and crystal dimensions. In the present study, it has been used to prepare PLA films with controlled surface texture.…”

High Performance Polarization‐Resolved Photodetectors Based on Intrinsically Stretchable Organic Semiconductors

“…Moreover, Table S1, Supporting Information, summarizes the detectivity and R ∥ /R ⊥ of polarization-resolved low-dimensional and organic photodetectors reported to date. [13,16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] To the best of our knowledge, our devices exhibit the best detectivity (>10 12 Jones), and it is worth mentioning other merits like LDR and f −3 dB are among the best-performed polarization-resolved photodetectors.…”

“…Recently, Conner group successfully aligned poly(benzodithiophene fluorinated benzotriazole) (PBnDT‐FTAZ) donor and poly(naphthalene diimide‐alt‐bithiophene) (N2200) acceptor blend film by combing mechanical rubbing and annealing processes, and subsequently achieved a polarization‐resolved photodetector. However, they found that it is difficult to obtain high responsivity and polarization sensitivity at the same time, [ 13 ] because the rubbing process scratches the film surface and thus deteriorates the device performance. Uniaxial straining is another alternative method to reorient the film.…”

“…To the best of our knowledge, this is the highest detectivity reported for intrinsically polarization-resolved photodetectors. [13,16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Further, we demonstrated a self-powered polarization imaging system and a full-Stokes polarimeter. Our results reveal that stretchable organic semiconductors are very promising for the future development of high-performance polarization-sensitive photodetectors.…”