Ferroelectric materials can be utilized for fabricating photodetectors because of the photovoltaic effect. Enhancing the photovoltaic performance of ferroelectric materials is still a challenge. Here, a self-powered ultraviolet (UV) photodetector is designed based on the ferroelectric BiFeO (BFO) material, exhibiting a high current/voltage response to 365 nm light in heating/cooling states. The photovoltaic performance of the BFO-based device can be well modulated by applying different temperature variations, where the output current and voltage can be enhanced by 60 and 75% in heating and cooling states, respectively. The enhancement mechanism of the photocurrent is associated with both temperature effect and thermo-phototronic effect in the photovoltaic process. Moreover, a 4 × 4 matrix photodetector array has been designed for detecting the 365 nm light distribution in the cooling state by utilizing photovoltage signals. This study clarifies the role of the temperature effect and the thermo-phototronic effect in the photovoltaic process of the BFO material and provides a feasible route for pushing forward practical applications of self-powered UV photodetectors.

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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...