Synergy Effect of a π‐Conjugated Ionic Compound: Dual Interfacial Energy Level Regulation and Passivation to Promote V_oc and Stability of Planar Perovskite Solar Cells

Abstract

Defects and energy offsets at the bulk and heterojunction interfaces of perovskite are detrimental to the efficiency and stability of perovskite solar cells (PSCs). Herein, we designed an amphiphilic π-conjugated ionic compound (QAPyBF 4 ), implementing simultaneous defects passivation and interface energy level alignments. The p-type conjugated cations passivated the surface trap states and optimized energy alignment at the perovskite/hole transport layer. The highly electronegative [BF 4 ] À enriched at the SnO 2 interface featured desired band alignment due to the dipole moment of this interlayer. The planar n-i-p PSC had an efficiency of 23.1 % with V oc of 1.2 V. Notably, the synergy effect elevated the intrinsic endothermic decomposition temperature of the perovskite. The modified devices showed excellent long-term thermal (85 °C) and operational stability at the maximum power point for 1000 h at 45 °C under continuous one-sun illumination with no appreciable efficiency loss.

Surface Re-Engineering of Perovskites with Buckybowls to Boost the Inverted-Type Photovoltaics

“…An even more widely known function of capping layers on perovskite surfaces is the chemical passivation-induced and energy level-matching-enabled minimization of recombination losses. − For example, one can intercalate coordinating molecules into the perovskite–ETL interface to simultaneously interact with the perovskite and fullerene, synergistically remedying the chemical and energy level mismatch problems as well as improving the device stability . Another effective strategy is to introduce 2D perovskite capping layers to 3D perovskite films to form a 2D–3D perovskite heterojunction.…”

A Multifunctional Fluorinated Polymer Enabling Efficient MAPbI3-Based Inverted Perovskite Solar Cells

“…Due to the intrinsic polycrystalline nature of perovskite, a considerable number of defects presence at grain boundaries and surfaces, especially the under-coordinated Pb 2+ ions, which tends to generate detrimental trap states and minimize V oc and FF as well as device PCE. 46,47 Furthermore, the volatile content of MA + inclines to separate from MAPbI 3 perovskite, leading to a deterioration of device stability. 22,23 Heteroatoms with unpaired electrons (i.e., sulfur (S), oxygen/carbonyl (C O), and nitrogen (N)) have been demonstrated to effectively passivate the under-coordinated Pb 2+ cation by forming strong noncovalent interaction.…”

“…Due to the intrinsic polycrystalline nature of perovskite, a considerable number of defects presence at grain boundaries and surfaces, especially the under-coordinated Pb 2+ ions, which tends to generate detrimental trap states and minimize V oc and FF as well as device PCE. , Furthermore, the volatile content of MA + inclines to separate from MAPbI 3 perovskite, leading to a deterioration of device stability. , Heteroatoms with unpaired electrons (i.e., sulfur (S), oxygen/carbonyl (CO), and nitrogen (N)) have been demonstrated to effectively passivate the under-coordinated Pb 2+ cation by forming strong noncovalent interaction. ,,,, In addition, the strong electronegativity of the F atom make it easy to associate with H atoms of MA + for perovskite via the N–H···F hydrogen bonds. ,, For p-iPSCs, the HTM layers were beneath the perovskite layer, the HTM films morphology significantly affects the subsequent crystallization of perovskite films. ,, Hence, the functional groups including “CO” and “F” atom were introduced into polymer BN-12. The interfacial interaction and passivation effect of HTMs with perovskite layer were investigated by the FTIR.…”

Molecular design for perovskite solar cells

“…For the perovskite/HTL interface, examples of organic molecules that have better chances to improve the device performance include those bearing ammonium and alkyl/phenyl groups, 306 provided that these molecules are compatible with the halide perovskite substrate 307,308 . The energy level arrangement of the perovskite/molecule/ETL and perovskite/molecule/HTL interface is critical for the device performance, because it dictates the energy loss and charge transfer kinetics at the interface 309‐314 …”

“…307,308 The energy level arrangement of the perovskite/molecule/ETL and perovskite/molecule/HTL interface is critical for the device performance, because it dictates the energy loss and charge transfer kinetics at the interface. [309][310][311][312][313][314] 4.5 | Molecular engineer ETL/metal, cathode, and carbon interfaces Organic molecules and polymers are applied to modify the ETL/metal and cathode interfaces, since the interfacial contact and the energy level alignment are often associated with the energy losses and degradation. 315 In addition, organic molecules are deposited at the ETL/metal 316,317 and ITO/C 60 318 interfaces to modify the hydrophobicity and water solubility that affect the device performance.…”