Improving the Performance of Printable Carbon Electrodes by Femtosecond Laser Treatment

Abstract

Low-cost carbon-conductive films were screen-printed on a Plexiglas® substrate, and then, after a standard annealing procedure, subjected to femtosecond (fs) laser treatments at different values of total accumulated laser fluence ΦA. Four-point probe measurements showed that, if ΦA > 0.3 kJ/cm2, the sheet resistance of laser-treated films can be reduced down to about 15 Ω/sq, which is a value more than 20% lower than that measured on as-annealed untreated films. Furthermore, as pointed out by a comprehensive Raman spectroscopy analysis, it was found that sheet resistance decreases linearly with ΦA, due to a progressively higher degree of crystallinity and stacking order of the graphitic phase. Results therefore highlight that fs-laser treatment can be profitably used as an additional process for improving the performance of printable carbon electrodes, which have been recently proposed as a valid alternative to metal electrodes for stable and up-scalable perovskite solar cells.

Low-Temperature Graphene-Based Paste for Large-Area Carbon Perovskite Solar Cells

“…As shown in Figure e, the use of graphene flakes enables the C-CEs to reach a resistivity as low as 0.07 ± 0.01 Ω cm, corresponding to an R sheet of ∼17 Ω sq –1 for a thickness of 40 μm. Such an R sheet is similar or inferior to the values reported for common transparent conductive oxide (TCO)-based CEs and C-CEs. , Remarkably, a reference paste without graphene shows a 5-fold increase of the resistivity compared to the graphene-based paste (resistivity = 0.35 ÷ 0.06 Ω cm). Thus, graphene-based C-CEs are expected to alleviate the drawback (e.g., low FF) related to the high series resistance of current collectors in large-area solar cells. , In addition, graphene-based films show optimal mechanical properties, which may be beneficial to tolerate thermomechanical stresses associated with natural weathering (day/night cycles, as simulated by the IEC 61215:2016 damp heat test) and metallization–encapsulation processes .…”

“…Such an R sheet is similar or inferior to the values reported for common transparent conductive oxide (TCO)based CEs and C-CEs. 72,73 Remarkably, a reference paste without graphene shows a 5-fold increase of the resistivity compared to the graphene-based paste (resistivity = 0.35 ÷ 0.06 Ω cm). Thus, graphene-based C-CEs are expected to alleviate the drawback (e.g., low FF) related to the high series resistance of current collectors in large-area solar cells.…”

Upscaling of Carbon-Based Perovskite Solar Module

“…Figure 4 A,B is reproduced from references [ 98 , 100 ], respectively. Figure 4 C,D is reproduced from references [ 102 , 103 ], respectively.…”

Annealing Engineering in the Growth of Perovskite Grains

“…[69][70][71]. In the fabrication of perovskite, the main electromagnetic waves that have been used in the perovskite annealing process are infrared light waves, visible light, lasers and microwaves [52,72,73]. The intense pulsed light is a non-contact rapid heating method which can offer fast millisecond pulses of broad spectrum light (190-1100 nm) from xenon lamps [74].…”

“…Lasers can provide a great strategy for modulating the crystallinity and electrical properties of films due to their high energy and excellent monochromatic characteristics, and are widely used in the fabrication of perovskite layers, such as the electron transport layer TiO 2 , the hole transport layer NiO, and the electrodes [73,[91][92][93]. Lasers also perform well in the promotion of crystallization of the functional layers [23,[94][95][96][97][98][99].…”