A new carbon phase with direct bandgap and high carrier mobility as electron transport material for perovskite solar cells

Abstract

Rapid development of perovskite solar cells is challenged by the fact that current semiconductors hardly act as efficient electron transport materials that can feature both high electron mobility and a well-matched energy level to that of the perovskite. Here we show that T-carbon, a newly emerging carbon allotrope, could be an ideal candidate to meet this challenge. By using first-principles calculations and deformation potential theory, it is found that T-carbon is a semiconductor with a direct bandgap of 2.273 eV, and the energy level in the conduction band is lower than that of perovskite by 0.5 eV, showing a larger force of electron injection. Moreover, the calculated electron mobility can reach up to 2.36 × 103 cm2 s–1 V–1, superior to conventional electron transport materials such as TiO2, ZnO and SnO2, which will facilitate more efficient electron separation and more rapid diffusion away from their locus of generation within the perovskite absorbers. Furthermore, the bandgap of T-carbon is highly sensitive to strain, thus providing a convenient method to tune the carrier transport capability. Overall, T-carbon satisfies the requirements for a potential efficient electron transport material and could therefore be capable of accelerating the development of perovskite solar cells.

Ternary chalcogenides XGaS2 (X = Ag or Cu) for photocatalytic hydrogen generation from water splitting under irradiation of visible light

“…The DP constant, E , is determined by E = (Δ E edge )/(Δ V / V 0 ), which denotes the energy change of CBM or VBM caused by the variation of volume. For the calculation of the bulk modulus and deformation potential constants, a 2 * 2 * 1 supercell, including 64 atoms for all structures, were constructed to apply strains . m * is the effective mass of electrons and holes and is determined using the equation , where ℏ , k , and E k are the reduced Planck constant, wave vector, and corresponding energy, respectively.…”

Three-dimensional graphene networks modified with acetylenic linkages for high-performance optoelectronics and Li-ion battery anode material

“…S3 a, c), meanwhile the p orbitals transitions is hugely enhanced since there are more p orbitals contribution from the two unpaired p orbitals in the acetylenic triple bonds. To the experimentally realized T-Carbon, Sun et.al [27] claim it is a good ETM for perovskite solar cells because of its moderate direct bandgap and small effective carrier mass, even superior to conventional ETMs such as TiO2, ZnO and SnO2. Through comprehensive comparison of the electron (hole) effective masses of CKL, CYKL and T-Carbon (see Table 2 and Fig.…”

Exploring T-carbon for energy applications

“…Compared with other allotropes of carbon, T-carbon has many unique and intriguing properties (Figure 1), suggesting that it could have a wide variety of potential applications in photocatalysis, solar cells, adsorption, energy storage, supercpacitors, aerospace materials, electronic devices, etc. For example, T-carbon is predicted to be a semiconductor with direct band gap of ∼3.0 eV at Γ-point (GGA: 2.25 eV; HSE06: 2.273 eV; B3LYP: 2.968 eV) 9,23 . The orbitals in T-carbon hybridize with each other and form anisotropic sp 3 hybridized bonds.…”

“…The bond strength is consistent with the bond length, which stabilize the structure by balancing the strain from the carbon tetrahedron cage. Moreover, the band gap could be effectively adjusted by doping elements or strain engineering to be suitable for photocatalysis and solar cells [23][24][25] . Particularly, the band gap can be tuned in the range of 1.62-3.63 eV with group IVA single-atom substitution, where the doped structures hold the stability 25 .…”