三維和準二維鹵化物鈣鈦礦金屬-半導體-金屬光感測器的穩定性和光電特性

Abstract

鹵化物鈣鈦礦(halide perovskites)以其卓越的光電性能、高載流子遷移率、可調控的能帶結構與能隙值和合成方法簡單又低成本的而聞名。應用於光感測器時，鹵化物鈣鈦礦有長的載流子遷移長度和高吸光系數等優異特性。不幸的是，由於其晶體結構，三維鹵化物鈣鈦礦存在穩定性問題。它容易受潮濕和室溫大氣的影響，使得元件易降解。因此，具有潛在光電應用的二維和準二維鹵化物鈣鈦礦被視為取代三維鹵化物鈣鈦礦的解決方案。然而，二維鹵化物鈣鈦礦具有較大的能隙和較低的載流子遷移率。這意味著這些材料吸光範圍較窄且電荷傳輸性能較差。為了克服這些挑戰，我們的研究目標是探討準二維鹵化物鈣鈦礦在何種層數(n)下能夠表現出更優異的光電性能和更佳的元件穩定性。在本研究中，我們成功地製備了金屬-半導體-金屬形式的光感測器，以二氧化矽作為基板，並在基板上鍍有指叉式鈦/金（5 奈米/50 奈米）電極，用於製作 Ruddlesden-Popper 相的PEA2MAn-1PbnI3n+1二維(n = 1)、準二維(n = 2 – 5)和三維(n = ∞)鹵化物鈣鈦礦光感測器。準二維鹵化物鈣鈦礦(n = 5)元件在 3 V 偏壓、650 nm 波長雷射照射時的光響應係數為 0.0022 mA/W。在室溫大氣環境條件下，經過 6 天後，光響應數值保持了原始值的 79%。同樣地，準二維鹵化物鈣鈦礦(n = 5)器件在 3 V 偏壓、450 nm 波長雷射照射時，光響應係數為 0.0047 mA/W，在室溫大氣環境下，經過 7 天後仍維持了 85%的原始值。相比之下，三維鹵化鈣鈦礦元件雖具有較高的光響應係數，在 3 V 偏壓、650 nm 雷射下的光響應係數為 0.12 mA/W，在 3 V 偏壓、450 nm 雷射下為 0.13 mA/W。然而，經過 6 天後，光響應在室溫大氣環境條件下分別降至原始值的 14%(650 nm 波長雷射及 3 V 偏壓)和 6.6%（450 nm 波長雷射及 3 V 偏壓）。準二維鹵化鈣鈦礦(n = 5)的光感測器在相對上具有較高的穩定性，但仍面臨著絕對光響應性較低的挑戰。

Halide perovskites (HPs) are known for their significant performance, high carrier mobility, tunable bandgap, and simple, low-cost synthesis processes. When applied to photodetector devices, halide perovskites exhibit outstanding features such as a long carrier diffusion length and large optical absorption coefficients. However, three-dimensional halide perovskites exhibit stability issues due to their crystal structure. Three-dimensional halide perovskites are vulnerable to humidity and ambient condition, which makes the devices easier to degrade. As a result, two-dimensional and quasi-two-dimensional HPs with the potential for optoelectronic applications are regarded as a solution to replace three-dimensional halide perovskites. Unfortunately, two-dimensional HPs have a larger bandgap and lower charge-carrier mobility. This means that these materials have a narrow absorption range and poor charge transport. In order to overcome the challenges, we aim to determine at what value of n, quasi-two-dimensional HPs can exhibit a broader absorption range and greater performance. Herein, we successfully fabricate two-dimensional HPs, quasi-two-dimensional HPs and three-dimensional HPs based photodetectors with the interdigitated Ti/Au (5 nm/50 nm) electrodes as a bottom contact on the substrate. The quasi-two-dimensional HPs (n = 5) device exhibits a higher stability with a responsivity of 0.0022 mA/W under 650 nm laser irradiation at the 3 V. The photoresponse retains 79% of its original value after 6 days under ambient condition. The quasi-two-dimensional HPs (n = 5) device shows a responsivity of 0.0047 mA/W under 450 nm laser irradiation at 3 V and the photoresponse retains 85% of its original value after 6 days under ambient condition. Compared with quasi-two-dimensional HPs (n = 5) device, three-dimensional HPs device initially exhibits higher responsivity of 0.12 mA/W under 650 nm laser at 3 V and 0.13 mA/W under 450 nm laser at 3 V. However, after 6 days, the photoresponse degraded to 14% under 650 nm laser irradiation at the 3 V bias and 6.6% under 450 nm laser irradiation at the 3 V under ambient condition. The quasi-two-dimensional HPs (n = 5) based photodetectors improved the stability, but still face the challenges of lower responsivity.