Photovoltaic–Pyroelectric Coupled Effect Based Nanogenerators for Self‐Powered Photodetector System

Abstract

seriously lowering the power conversion efficiency. [13][14][15][16] The photocurrent of ferroelectric devices is determined by the light adsorption process, dissociation efficiency of electron-hole pairs, lifetime and the mobility of charges. [17] As is known, most of the ferroelectric materials have small absorption coefficient and large bandgap of 2.6-4 eV, thus can only scavenge a little amount of solar energy in the UV range or near UV range of sunlight. According to the Glass model, driven by the noncentral symmetric potential well, the excited electrons only can shift several angstorms along the polarization direction before they decay, leading to very small photocurrent in ferroelectric-photovoltaic devices. Moreover, the lifetime of the photogenerated nonequilibrium charges was only in the picosecond scale, while the recombination lifetime was measured to be submicrosecond to tens of microseconds. [17] Therefore, owing to the very small photocurrent, it seems to be difficult for ferroelectric materials superior to classical semiconductor in mainstream usage of photovoltaic devices. However, these materials could be more appealing for some specific applications due to their multifunctionalities. For instance, most of the ferroelectric materials have bandgaps of 2.6-4 eV, which only can absorb a certain range of wavelength in sunlight with photons energies above bandgap energy. [17,18] Therefore, besides as nanogenerators for scavenging solar energy, ferroelectric photovoltaic devices may be more suitable for fabricating photodetectors to detect a certain wavelength light.Among the conventional ferroelectric materials, BiFeO 3 (BFO) has the narrowest bandgap of about 2.67 eV, which can absorb the light wavelengths of less than 465 nm. [19] Thus BFObased ferroelectric-photovoltaic devices could be well utilized to detect 450 nm light in the range of visible light. Moreover, as a multifunctional material, BFO possesses both the photovoltaic and pyroelectric effects, offering more opportunities for such applications. When 450 nm light is illuminating on BFO surface, electrical signals could be detected due to the generation and separation of electron-hole pairs. However, it is suggested that being different from traditional p-n junction based semiconductor, the photovoltaic effect of BFO may be associated with noncentral symmetric structure, domain wall, Schottky barrier, and depolarization field. [17] In addition, due to the noncentral symmetric crystal structure, pyroelectric signals can be generated by the light-induced temperature increase Ferroelectric material BiFeO 3 with narrow bandgap of 2.67 eV can be more suitable to fabricate photodetectors instead of solar energy harvesters because of low energy conversion efficiency. Herein, a BiFeO 3 film-based self-powered photodetector is reported by using the photovoltaic-pyroelectric coupled effect to enable a fast sensing of 450 nm light illumination. Compared with photovoltaic effect, the photosensitivity parameters including photoconductive gain, respons...

Structure, Performance, and Application of BiFeO3 Nanomaterials

“…Here, we summarized several representative morphologies to discuss the developments of BFO-based nanomaterials ( Fig. 1) [18][19][20].…”

“…After BFO ceramic was firstly synthesized in 1957, it has become one of important BFO-based nanomaterials ( Fig. 1a-d) [19][20][21][22]. However, it is still challenging to synthesize a single-phase BFO ceramic because the volatility of Bi 3+ and aggregation of oxygen vacancies can result in the occurrence of some secondary phases during the sintering process.…”

“…Figure 1i-p displays the BFO nanostructures with different morphologies, including nanodots, nanofibers, nanosheet, nanoplate, nanotubes, nanoislands, nanoparticles, Refs. [19][20][21][22]. e-h SEM images of BFO thin films.…”

Structural Design and Pyroelectric Property of SnS/CdS Heterojunctions Contrived for Low‐Temperature Visible Photodetectors

“…Along with the photogenerated charge carriers induced by photoelectricity, there are also extra pyroelectric polarization charges under illumination in some materials with inherent polarization, like ferroelectrics materials BiFeO 3 , [ 13 ] BaTiO 3 , [ 14,15 ] Pb(Zr,Ti)O 3 , [ 16 ] and pyroelectric material ZnO, [ 17–20 ] etc. Furthermore, the generated polarization charges can effectively modulate the behavior of photoinduced electrons, such as separation, transition, and recombination within heterojunctions.…”

Self‐Powered Photodetectors Based on 2D Materials

“…[47][48][49] The response mechanisms of these self-powered photodetectors are based on the photovoltaic effect of semiconductors, i.e., semiconductors produce photogenerated electron-hole pairs under illumination conditions. [50][51][52] The photocurrent is generated by the separation of photogenerated electrons and holes, and the directional movement of photogenerated electrons. The difference is that the p-n junction photodetector and the Schottky junction photodetector promote the separation of photogenerated electron-hole pairs by the built-in electric field.…”