Piezophototronic Effect Enhanced Photoresponse of the Flexible Cu(In,Ga)Se₂ (CIGS) Heterojunction Photodetectors

Abstract

The Cu(In,Ga)Se 2 (CIGS) heterojunction, as a mature and high efficiency thin-film solar cell, is rarely studied as a photodetector, especially in flexible substrates. In this paper, the structure of an ITO/ZnO/CdS/CIGS/ Mo heterojunction is grown on the polyimide (PI) substrate to form a flexible CIGS heterojunction photodetector. The photodetector can work in a very wide band ranging from 350 to 1200 nm with responsivity up to 1.18 A W −1 (808 nm), detectivity up to 6.56 × 10 10 Jones (cmHz 1/2 W −1 ), and response time of 70 (/88) ms, respectively. Moreover, the piezophototronic effect is first used to investigate performance modulation of this device by effectively controlling the separation and transport of carriers at the interface of CdS/ZnO. Interestingly, by externally applying a 0.763% tensile strain, the photoresponsivity and detectivity of the photodetector exhibit a decrease from 1.18 to 0.88 A W −1 , and from 6.56 × 10 10 to 4.81 × 10 10 Jones, respectively, while under a -0.749% externally static compressive strain, the photoresponsivity could be enhanced by ≈75.4% with a maximum of 2.07 A W −1 , and the detectivity is improved by ≈66.1% with its peak value up to 10.9 × 10 10 Jones. Meanwhile, the response time can be modulated from 99(/116) to 41.3(/42.6) ms. This work suggests that the CIGS heterojunction has great potential in novel applications for piezophototronic sensors and also gives a hint to modulate the performance of other multilayer heterostructures via the piezotronic effect.

Si/CuIn0.7Ga0.3Se2 Core–Shell Heterojunction for Sensitive and Self‐Driven UV–vis–NIR Broadband Photodetector

“…Meanwhile, this photodetector exhibits excellent characteristics in terms of broad photoresponse range from 300 to 1100 nm, large responsivity of 0.33 A W −1 , ultrahigh detectivity of 1.6 × 10 13 Jones, fast response speed of 823/356 µs, and robust stability. The performance characteristics are comparable to or surpass those reported for Si or CIGS‐based photodetectors in previous work, as shown in Table 1 …”

“…CuIn x Ga 1− x Se 2 (CIGS) in its chalcopyrite phase has attracted considerable interest as a promising p‐type light absorber, owing to its tunable band energy (1.0–1.7 eV), large optical absorption coefficient (≈10 5 cm −1 ), outstanding thermal, environmental and electrical stabilities . In terms of application, CIGS thin films have been used in thin‐film solar cells, solar modules, and photoelectrochemical photocathodes .…”

“…The above‐stated excellent features also make CIGS great potential application in broadband photodetection. For example, Pan and co‐workers designed an indium tin oxide (ITO)/ZnO/CdS/CIGS/Mo heterojunction on the polyimide substrate to form a flexible CIGS heterojunction photodetector . Wang and co‐workers demonstrated a visible–NIR optical position sensitive detectors based on Mo/CIGS/CdS/ZnO/ITO/glass structure .…”

On the Piezo‐Phototronic Effect in Si/ZnO Heterojunction Photodiode: The Effect of the Fermi‐Level Difference

“…Recently, the piezo‐phototronic effect was extensively utilized to enhance the performances of advanced optoelectronic devices such as photodiodes (PDs), [ 1–12 ] solar cells, [ 13–18 ] and light‐emitting diodes. [ 19–25 ] The basic principle of the piezo‐phototronic effect is the external strain‐induced energy band structure modulation at the local interface of a p‐n junction or a Schottky junction.…”

“…More than hundreds of works show that the piezo‐phototronic effect has greatly improved the performances of advanced optoelectronic devices. [ 1–25 ] Nevertheless, due to the great differences in the energy band structures among different types of optoelectronic devices, the modulation effects in their energy bands are quite distinctive, resulting in different magnitude of their performances improvement. [ 29–32 ] Furthermore, not only positive effects, but also negative effects may be produced in some types of energy band structures, leading to the restriction or even the reduction of performance.…”