Copper Thiocyanate and Copper Selenocyanate Hole Transport Layers: Determination of Band Offsets with Silicon and Hybrid Perovskites from First Principles

Abstract

Copper thiocyanate (CuSCN) and copper selenocyanate (CuSeCN) combine a high work function with a high optical transparency. To elucidate their potential as transparent hole selective materials, herein, first‐principles calculations of the structural and electronic properties are reported, with special attention to the band offsets with crystalline Si and hybrid perovskites (CH3NH3PbI3, CH3NH3PbBr3, and CHN2H4PbBr3). The structural parameters and electronic band structure are obtained using the Perdew–Burke–Ernzerhof functional, resulting in indirect and direct bandgaps of 2.13 and 1.81 eV for CuSCN and CuSeCN, respectively. The (100) surfaces of the two materials do not feature in‐gap states, maintaining the semiconducting nature. Band offsets are determined by the electrostatic potential lineup method using slab calculations. Small valence band offsets of 0.10 eV for CuSCN/Si and 0.08 eV for CuSCN/CH3NH3PbI3 are desirably found, i.e., a promising hole transport layer character of CuSCN for Si and CH3NH3PbI3‐based solar cells. Type‐II band alignment is obtained for all studied heterojunctions.

Cl2-Doped CuSCN Hole Transport Layer for Organic and Perovskite Solar Cells with Improved Stability

“…In organic light-emitting diodes (OLEDs), CuSCN has been traditionally used as an HTL to improve the charge injection efficiency. Its high optical transparency suppresses any parasitic absorption of the light generated from the active layer. − In organic and perovskite solar cells (OSCs and PSCs), the CuSCN layer allows the extraction of holes from the photoactive layer, again suppressing any parasitic absorption and allowing the incident radiation of all wavelengths to reach the photoactive layer. − Theoretical studies have linked the advantages of CuSCN as an HTL to its usual lack of any deep carrier trap states and its minimal valence band offset with the archetypal perovskite CH 3 NH 3 PbI 3 . In ultraviolet-based photodetectors (UVPDs), the wide bandgap of CuSCN allows unhindered high absorption in the UV region and could form not only metal–semiconductor–metal (MSM) UVPDs but also p-n junction UVPDs when combined with n -type material. − Finally, CuSCN is one of the few materials for p -channel thin film transistor (TFT) fabrication due to its hole transport selectivity. − …”

“…Finally, to gain a deeper understanding of atomic-scale effects related to the chlorination of CuSCN films, we performed density functional theory (DFT) calculations using the Vienna Ab-initio Simulation Package (VASP) software, , a plane-wave basis with an energy cutoff of 400 eV, projector augmented waves (PAW), and the generalized gradient approximation (GGA) Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional. Our focus here is mainly on the chlorination of CuSCN surfaces, in particular the nonpolar (100) and (010) surfaces (Figure ) which have low formation energies .…”

Interlayer Coupling Induced Phonon-Glass–Electron-Crystal Behavior in van der Waals Heterostructure PtSe2/γ-GeSe

“…Ab initio molecular dynamics simulations employing Andersen thermostats are used to address the thermal stability of heterostructure PtSe 2 /γ-GeSe. The electrostatic potential lineup method is employed to estimate the valence and conduction band offsets …”

Recombination junctions for efficient monolithic perovskite-based tandem solar cells: physical principles, properties, processing and prospects

“…25 A prominent example is to replace the Si(p + ) film with high workfunction HTLs, such as MoO x , which have proven to lead to high singlejunction device performance. 37 Alternative HTL materials for the c-Si subcell can be VO x , WO x CuO x , and CuSCN; [38][39][40] NiO x is also a potential candidate, but interfacing NiO x with c-Si remains challenging; doping the NiO x may potentially resolve this issue. 41 The transition metal oxides MoO x , VO x , and WO x are particularly interesting: due to their high workfunction, they act as effective HTLs for c-Si solar cells.…”