Hybrid Interfacial Engineering: An Enabling Strategy for Highly Sensitive and Stable Perovskite Quantum Dots/Organic Heterojunction Phototransistors

Abstract

All-inorganic lead halide perovskite quantum dots (PQD) have attracted tremendous research interest in the field of phototransistors due to their excellent optoelectronic properties. However, the inefficient charge transport/extraction and high trap-state density of the assembled PQD films seriously limit the photoresponsivity of PQD-based phototransistors. Herein, we demonstrate that these limits can be overcome by adopting a novel device architecture composed of a polar-polymer capping layer on a PQD/organic semiconductor (OSC) heterojunction. The polar polymer film plays the role of both electron trapping and encapsulation, whereas OSC provides the fast transport tracks for charges and PQD serves as the photoactive materials. Owing to the balanced dynamic processes of photogenerated charges, highly sensitive photodetection is achieved, as demonstrated by the peak photosensitivity of 1.5 × 104, a photoresponsivity of 2.1 × 104 A/W, a detectivity of 1 × 1015 Jones, and a high gain of 6.4 × 104 under weak incident light of 3 μW/cm2. Additionally, the phototransistors exhibit superior stability and reproducibility with negligible changes in the output current both in darkness and under illumination after storing for 4 months. The results demonstrate the promising potentials of the polar polymer/PQD/OSC heterojunction for high-performance photodetectors, and the mechanism and strategy described here can be applied to other kinds of quantum dots-based optoelectronic devices.

Supersensitive and Broadband Photodetectors Based on High Concentration of Er3+/Yb3+ Co‐doped WS2 Monolayer

“…The laser illumination area is measured to be 113 mm 2 (Figure S6, Supporting Information), which is much larger than the channel area of the device (0.0009 mm 2 ). The devices are illuminated by a 635 nm laser with the incident laser power density from 0 to 160.2 mW cm −2 at a bias from -1 to 1 V. Key parameters, including photocurrents (I ph ) photoresponsivity (R 𝜆 ), external quantum efficiency (EQE), specific detectivity (D*), and carrier mobility are evaluated by the following equations: [52][53][54][55][56] I ph = I photo − I dark (4)…”

“…The laser illumination area is measured to be 113 mm 2 (Figure S6, Supporting Information), which is much larger than the channel area of the device (0.0009 mm 2 ). The devices are illuminated by a 635 nm laser with the incident laser power density from 0 to 160.2 mW cm −2 at a bias from ‐1 to 1 V. Key parameters, including photocurrents ( I ph ) photoresponsivity ( R λ ), external quantum efficiency (EQE), specific detectivity ( D *), and carrier mobility are evaluated by the following equations: [ 52–56 ] $$$$\begin{equation}{I}_{{\mathrm{ph}}} = {I}_{{\mathrm{photo}}}\ - {I}_{{\mathrm{dark}}}\end{equation}$$$$ $$$$\begin{equation}{R}_{{\lambda}} = \frac{{{I}_{{\mathrm{ph}}}}}{{P \cdot S}}{\mathrm{\ \ }}\end{equation}$$$$ $$$$\begin{equation}EQE = \frac{{{R}_\lambda \cdot h \cdot c}}{{e \cdot {{\lambda}}}}\end{equation}$$$$ $$$$\begin{equation}{D}^* = \frac{{{R}_\lambda \cdot \sqrt S }}{{\sqrt {2{\mathrm{e}}{I}_{{\mathrm{dark}}}} }}\end{equation}$$$$ $$$$\begin{equation}\mu \ = \frac{L}{W}\ \ \frac{d}{{{\varepsilon }_0{\varepsilon }_r{V}_{DS}}}\ \frac{{{\mathrm{d}}{I}_{DS}}}{{{\mathrm{d}}{V}_g}}\end{equation}$$$$where I dark and I photo are the dark current and currents under 635 nm laser illu...…”

Thermally Activated Delayed Fluorescence Triplet State Excitons for High‐Performance Organic Photodetectors: A Novel Strategy

“…[ 23 ] proposed a hybrid‐layered phototransistor structure with a 2,7‐Dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT) channel layer, a photoactive layer of C8‐BTBT: [6,6]‐Phenyl C61 butyric acid methyl ester (PC 61 BM), and a molybdenum trioxide (MoO 3 ) interlayer. Although the results of R = 8.6 × 10 3 A W − 1 and D * = 3.4 × 10 14 Jones were obtained, the response time was 0.5 s. Recently, CsPbBrI 2 perovskite quantum dots/Poly[2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene] (PBTTT‐C 14 ) polymer heterojunction phototransistor achieved an R of 2.1 × 10 4 A W −1 at a rise time of 0.4 s. [ 24 ] These results demonstrate the importance of weighing the trade‐off between high gain and reasonable response speed when designing a high‐performance photodetector.…”