Low‐Temperature‐Processed Zr/F Co‐Doped SnO₂ Electron Transport Layer for High‐Efficiency Planar Perovskite Solar Cells

Abstract

The energy band position and conductivity of electron transport layers (ETLs) are essential factors that restrict the efficiency of planar perovskite solar cells (p‐PSCs). Tin oxide (SnO2) has become a primary material in ETLs due to its mild synthesis condition, but its low conduction band position and limited intrinsic carriers are disadvantageous in electron transport. To solve these problems, this work exquisitely designs a Zr/F co‐doped SnO2 ETL. The doping of Zr can raise the conduction band of SnO2, which reduces the energy barrier in electron extraction and inhibits the interface recombination between the ETL and perovskite. The open‐circuit voltage (VOC) of p‐PSCs consequently increases. F− doping belongs to n‐type doping. Thus, it equips SnO2 with a large number of free electrons and improves the conductivity of the ETL and short‐circuit current (JSC). The device based on Zr/F co‐doped ETL achieves a high efficiency of 19.19% and exhibits a reduced hysteresis effect, which is more satisfactory than that of a pristine device (17.35%). Overall, this research successfully adjusts the energy band match and boosts the conductivity of ETL via Zr/F co‐doping. The results provide an effective strategy for fabricating high‐efficiency p‐PSCs.

CsPbBr3 Nanocrystal Induced Bilateral Interface Modification for Efficient Planar Perovskite Solar Cells

“…The energy level alignment is another essential factor for efficient electron extraction. [ 37 , 38 ] Based on the information of the ultroviolet photoelectron spectra (UPS) in Figure S15a–d , Supporting Information, the position distributions of the conduction bands (CB), valence bands, and Fermi levels ( E f ) for PSK and CN are calculated (Figure S15e , Supporting Information). [ 39 ] As shown in Figure S15f , Supporting Information, the CB of CN is located between the CB of SnO 2 and MAPbI 3 perovskite, implying CN bottom modification is able to decrease the energy barrier between the SnO 2 /perovskite interface and reduce the energy loss during the electron transport.…”

Cesium Iodide Incorporation in Tin Oxide Electron Transport Layer for Defect Passivation and Efficiency Enhancement in Double Cation Absorber‐Based Planar Perovskite Solar Cells

“…The CsI doping in SnO x film upshifts the Fermi level up to 50 meV compared with bare SnO x as discussed earlier and the upshift of Fermi level in CsI–SnO x can effectively extract electrons from perovskite highest occupied molecular orbital (HOMO) level due to improved n‐type behavior than bare SnO x . [ 30,82 ] Similarly, holes are screened from spiro‐OMeTAD hole selective layer with its optimum lowest unoccupied molecular orbital (LUMO) energy level with the perovskite absorber. To further understand the interface recombination mechanism, the diode ideality factor ( n id ) measurements were carried out using light intensity‐dependent V oc measurements.…”

“…to control the mobility, band edge tuning, and defect density of the bulk SnO x . [ 27–36 ] 2) surface passivation strategy is used to suppress the dangling bonds (undercoordinated sites) in SnO x surface using electropositive and electronegative molecules which helps in fine‐tuning the surface work function and defect density with respect to the top perovskite layer and thereby improving the charge extraction process. Electropositive molecules like phosphoric acid, acetic acid, and electronegative molecules like (NH 4 ) 2 S are used to control the corresponding defects on the SnO x surface.…”

Graphene‐Based Materials in Planar Perovskite Solar Cells

“…[ 127,128 ] SnO 2 is currently considered as the most promising ETL in fabricating highly efficient planar PSCs because of its higher mobility, wider bandgap, and deeper conduction band than TiO 2 . [ 129 ] However, SnO 2 ‐based planar PSCs synthesized at low temperatures suffer from severe hysteresis, and the charge extraction efficiency of SnO 2 ETLs requires improvement. Xie et al [ 130 ] obtained a high‐performance regular planar PSC with negligible hysteresis utilizing GQD‐modified SnO 2 ETLs.…”