Significantly Enhanced Detectivity of CIGS Broadband High-Speed Photodetectors by Grain Size Control and ALD-Al₂O₃ Interfacial-Layer Modification

Abstract

The Cu(In,Ga)Se 2 (CIGS) thin film has been commercialized as solar cells with great success, but its application for photodetectors still faces some practical challenges, including low detectivity and long response time. In this paper, the structure of the Mo/CIGS/CdS/ZnO/ITO heterojunction has been fabricated, and satisfactory performances of high detectivity and fast response time have been achieved by suppressing the dark current and enhancing the carrier mobility. The controllable growth of CIGS grains is accomplished through optimizing the selenization process, demonstrating that bigger grain sizes resulted in higher carrier mobility and better response characteristics. Particularly, the high rise/decay speed of 3.40/6.46 μs is achieved. Furthermore, the interface of the CIGS/CdS heterojunction has been modified by the Al 2 O 3 layer via the atomic-layer deposition (ALD) process. The dark current of the device is effectively suppressed by the ALD-Al 2 O 3 layer, which remarkably drops from ∼10 −7 to ∼10 −9 A. As a consequence, the detectivity rises from 3.08 × 10 11 to 1.84 × 10 12 Jones. In addition, the ALD-Al 2 O 3 layer shows a protective effect as well, which is positive for photoelectrical conversion. Besides, the wide linear dynamic range of 102.1 dB and large −3 dB bandwidth of 78 kHz are acquired. This work suggests that the CIGS-based heterojunction has great potential for high-performance thin-film photodetectors.

Reducing current fluctuation of Cs3Bi2Br9 perovskite photodetectors for diffuse reflection imaging with wide dynamic range

“…First, as shown in Fig. 1d, e, ALD-TiO 2 layer can effectively improve the quality of thin films [25]. Thus, it can suppress the defects and reduce the surface carrier recombination, and then both the intensity and fluctuation of surface dark current can be suppressed.…”

“…The average grain sizes of bare Cs 3 Bi 2 Br 9 and TiO 2 /Cs 3 -Bi 2 Br 9 are estimated to be~90 and~180 nm, respectively. The improvement of perovskite film quality is mainly attributed to the Bi-O interfacial interaction at substrate/perovskite interface [25].…”

“…In this paper, for the first time we fabricate lead-free Cs 3 Bi 2 Br 9 perovskite PD, and build a prototype of this perovskite PD-based imaging system with diffuse reflection imaging mode. Moreover, we propose a new parameter F related to light current fluctuation to evaluate imaging performance of a PD, and prove its usability by comparison of unoptimized Cs 3 Bi 2 Br 9 PD and optimized Cs 3 Bi 2 Br 9 PD by atomic layer deposition (ALD) technique [24,25]. The experimental results show that the optimized Cs 3 Bi 2 Br 9 PD with 0.5-nm ALD-TiO 2 layer possesses smaller light current fluctuation, i.e., smaller F value, thus resulting in better imaging performance.…”

Silver Surface Treatment of Cu(In,Ga)Se2 (CIGS) Thin Film: A New Passivation Process for the CdS/CIGS Heterojunction Interface

“…[ 2–4 ] Highly efficient CIGS‐based solar cells possess a multilayer stacked structure, which includes a p‐type CIGS absorber layer, an n‐type buffer layer (CdS or Zn(O,S)), and a transparent conductive oxide (TCO: ZnO and aluminum (Al)‐doped ZnO). [ 5–7 ] In consequence, interface engineering of the CIGS‐based solar cell plays a critical role in the improvement of device performance, particularly for the CdS/CIGS heterojunction interface. [ 8 ] Generally, serious carrier recombination can be observed at the CdS/CIGS interface when deep acceptor defects (such as ) are unoccupied at the Fermi level, [ 9–12 ] which is detrimental to device performance.…”

All‐Inorganic Perovskite Photodetectors with Ultrabroad Linear Dynamic Range for Weak‐Light Imaging Applications

“…An effective strategy is introducing interfacial passivation layers by atomic layer deposition (ALD) technique. [ 21–24 ] ALD can synthesize thickness‐controlled, dense, and uniform thin films at low temperature, [ 25 ] which meets the critical demands for the heterojunctions fabrication. Rehman et al.…”