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

Abstract

Copper­(I) thiocyanate (CuSCN) is a stable, low-cost, solution-processable p-type inorganic semiconductor used in numerous optoelectronic applications. Here, for the first time, we employ the time-of-flight (ToF) technique to measure the out-of-plane hole mobility of CuSCN films, enabled by the deposition of 4 μm-thick films using aerosol-assisted chemical vapor deposition (AACVD). A hole mobility of ∼10–3 cm2/V s was measured with a weak electric field dependence of 0.005 cm/V1/2. Additionally, by measuring several 1.5 μm CuSCN films, we show that the mobility is independent of thickness. To further validate the suitability of our AACVD-prepared 1.5 μm-thick CuSCN film in device applications, we demonstrate its incorporation as a hole transport layer (HTL) in methylammonium lead iodide (MAPbI3) perovskite solar cells (PSCs). Our AACVD films result in devices with measured power conversion efficiencies of 10.4%, which compares favorably with devices prepared using spin-coated CuSCN HTLs (12.6%), despite the AACVD HTLs being an order of magnitude thicker than their spin-coated analogues. Improved reproducibility and decreased hysteresis were observed, owing to a combination of excellent film quality, high charge-carrier mobility, and favorable interface energetics. In addition to providing a fundamental insight into charge-carrier mobility in CuSCN, our work highlights the AACVD methodology as a scalable, versatile tool suitable for film deposition for use in optoelectronic devices.

All-Inorganic Hydrothermally Processed Semitransparent Sb2S3 Solar Cells with CuSCN as the Hole Transport Layer

“…The hole mobility (μ h ) was calculated in the SCLC regime as 1.74 (±0.61) × 10 –4 cm 2 V –1 s –1 . This value is lower than those reported by other measurement techniques such as field-effect mobility (0.1 cm 2 V –1 s –1 ) or time-of-flight (∼10 –3 cm 2 V –1 s –1 ) . However, SCLC mobility is more realistic for solar cell application since the film thickness is the same range as the solar cell (the time-of-flight technique uses films in μm thickness range) and the mobility is calculated across the thickness of the film (in contrast to field-effect mobility, where mobility is calculated in in-plane direction) .…”

“…This value is lower than those reported by other measurement techniques such as field-effect mobility (0.1 cm 2 V –1 s –1 ) 12 or time-of-flight (∼10 –3 cm 2 V –1 s –1 ). 40 However, SCLC mobility is more realistic for solar cell application since the film thickness is the same range as the solar cell (the time-of-flight technique uses films in μm thickness range) and the mobility is calculated across the thickness of the film (in contrast to field-effect mobility, where mobility is calculated in in-plane direction). 40 To measure the conductivity and verify the nature of CuSCN/Au contact (ohmic or Schottky), a device with the structure FTO/Au/CuSCN/Au was prepared ( Figure 1 c).…”

“… 40 However, SCLC mobility is more realistic for solar cell application since the film thickness is the same range as the solar cell (the time-of-flight technique uses films in μm thickness range) and the mobility is calculated across the thickness of the film (in contrast to field-effect mobility, where mobility is calculated in in-plane direction). 40 To measure the conductivity and verify the nature of CuSCN/Au contact (ohmic or Schottky), a device with the structure FTO/Au/CuSCN/Au was prepared ( Figure 1 c). An ohmic contact was formed between CuSCN and Au, which is important for efficient charge extraction and reduction of the recombination losses.…”

Revamping Triboelectric Output by Deep Trap Construction

“…As it is difficult to identify the location of transit time ( t tr ) in the linear plot (Figure 2c inset), a logarithmic plot was used to identify t tr . The t tr value was obtained from the intersection of the linear regions [ 51 ] shown in Figure 2c. The results show that the carrier transit time in pure PET and KH556@PET films are 4.2 and 6.1 s, respectively, indicating that the latter contains more traps that impede carrier migration.…”

Recent Advance in Solution‐Processed Hole Transporting Materials for Organic Solar Cells

“…And the preparation of MoO 3 through energy-consuming vacuum evaporation certainly limits its use in the large-scale manufacturing. [16,17] In recent years, great effort has been devoted to developing new kinds of HTL materials, such as conjugated polyelectrolytes, [18][19][20] graphene oxides, [21][22][23][24][25] inorganic compounds, [26,27] self-assembled monolayer [28,29] and organic small molecules, [30,31] but most of these materials suffer from inferior charge transport property, poor film-forming ability and complicated preparation, limiting their further applications for anode modifications in OSCs. In particular, the use of inferior HTLs has been proved to cause serious problems of V oc loss, low fill factor (FF), and poor device stability, which severely degrades the OSC performances.…”