Low Temperature Scalable Deposition of Copper(I) Thiocyanate Films via Aerosol-Assisted Chemical Vapor Deposition

Abstract

Copper­(I) thiocyanate (CuSCN) is a stable, wide bandgap (>3.5 eV), low-cost p-type semiconductor widely used in a variety of optoelectronic applications, including thin film transistors, organic light-emitting diodes, and photovoltaic cells. For CuSCN to have impact in the commercial fabrication of such devices, large-area, low-cost deposition techniques are required. Here, we report a novel technique for deposition of CuSCN that addresses these challenges. Aerosol-assisted chemical vapor deposition (AACVD) is used to deposit highly crystalline CuSCN films at low temperature. AACVD is a commercially viable technique due to its low cost and inherent scalability. In this study, the deposition temperature, CuSCN concentration and carrier gas flow rate were studied and optimized, resulting in homogeneous films grown over areas approaching 30 cm2. At the optimized values, i.e., 60 °C using a 35 mg/mL solution and a carrier gas flow rate of 0.5 dm3/min, the film growth rate is around 100 nm/min. We present a thorough analysis of the film growth parameters and the subsequent morphology, composition, and structural and optical properties of the deposited thin films.

Novel scalable aerosol-assisted CVD route for perovskite solar cells

“…Many oxides that are commonly used as electrontransport layers (ETLs) in PSCs have also been deposited by AACVD, [11][12][13] and we have recently reported deposition of CuSCN via AACVD, 14 which has been used as a hole transport layer (HTL) in PSCs. 15 So far, several groups have demonstrated deposition of organo-metal halide perovskites using AACVD, utilising either a 1-step or 2-step method. 16-19 1-Step deposition generally led to powdery deposits as the precursors tend to homogenously nucleate in the gas phase.…”

Determining Out-of-Plane Hole Mobility in CuSCN via the Time-of-Flight Technique To Elucidate Its Function in Perovskite Solar Cells

“…Second, smoother films of CuSCN form on MAPbI 3 , reducing the thickness error during the final measurement. Through atomic force microscopy (AFM) measurements (Figure S3), it was found that a CuSCN layer with 30% lower root mean square (RMS) roughness (64 nm) was formed on MAPbI 3 in comparison to the CuSCN layer deposited on FTO, which exhibited an RMS roughness of 92 nm . Lastly, the addition of MAPbI 3 better represents the PSC structure.…”

“…The solution was filtered prior to deposition. Deposition was conducted at 60 °C, and a N 2 flow rate of 0.5 dm 3 /min was used . Postdeposition, substrates were transferred to a N 2 -filled glovebox and left for 12 h to dry.…”

“…To form 1.5 and 4 μm CuSCN layers for ToF, filtered 20 and 40 mL solutions of 35 mg/mL CuSCN (99%, Sigma-Aldrich) in diethyl sulfide (DES 98%, Sigma-Aldrich) were deposited in a custom-made AACVD reactor in a well-ventilated fume hood at 60 °C and a N 2 flow rate of 0.5 dm 3 /min. 42 Full details are reported in a previous study. 42 Gold (Au) (100 nm) was thermally evaporated to form the counter electrode.…”

“…Since then, CuSCN has been incorporated in various n-i-p and p-i-n architectures, resulting in champion PCEs of 20.4 and 16.6%, respectively. , Because of the ease of processing, CuSCN has been deposited using various techniques, including spin coating, , spray coating, drop casting, doctor blading, and electrodeposition . Most recently, we have shown that a scalable technique, aerosol-assisted chemical vapor deposition (AACVD), can be used to deposit CuSCN with a minimum thickness of 1.5 μm . Until now, there have been no reports on PSC device performance when AACVD is employed for CuSCN deposition, whereas PCEs have been reported for CuSCN deposited by each of the other techniques stated above, ranging from 6.4% for drop-cast CuSCN to 20.4% for spin-coated CuSCN. , It should be noted that 20.4% PCE was achieved by incorporating a triple-cation perovskite and reduced graphene oxide interlayer …”