Revealing the Mechanism of π Aromatic Molecule as an Effective Passivator and Stabilizer in Highly Efficient Wide‐Bandgap Perovskite Solar Cells

Abstract

Trap‐induced nonradiative recombination and decomposition are the major limiting factors that hinder the development of mixed‐halide wide‐bandgap perovskite solar cells. Specifically, the incorporation of formamidinium (FA+) and bromide in wide‐bandgap (WBG) perovskite materials leads to shallow‐energy‐level traps and inferior light stability. Herein, the electron‐withdrawing molecule 2,3,5,6 tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TCNQ) is used as an effective passivator and stabilizer, which has molecular interaction with the FA+ cation for reducing trap densities and enhancing the stability of WBG perovskite solar cells. It is found that the extended π aromatic system in F4‐TCNQ can enhance the binding energy and stabilize the FA+ cation in perovskite films. Furthermore, the 1.67 eV bandgap inverted perovskite solar cells with a small amount of F4‐TCNQ have shallower defect levels, reduced trap density, and decreased nonradiative recombination, therefore giving a remarkably improved power conversion efficiency (PCE) of 20.0%. Most importantly, the unencapsulated devices with F4‐TCNQ additive have greatly enhanced stability, maintaining 88% of their peak PCEs under continuous illumination after 840 h, whereas the control devices only retain 48% of their PCEs after 500 h.

Efficient and Stable Wide‐Bandgap Perovskite Solar Cells Derived from a Thermodynamic Phase‐Pure Intermediate

“…[37][38][39] Since then, tremendous efforts have been devoted to the composition and crystallization engineering in Cs x FA 1-x Pb(I y Br 1-y ) 3 for the development of wide-bandgap perovskite solar cells. [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] The preparation of high-quality perovskite thin films is very important to guarantee their efficient performance in solar cells. One-step antisolvent methods were frequently employed in the preparation of Cs x FA 1-x Pb(I y Br 1-y ) 3 thin films.…”

“…[ 37–39 ] Since then, tremendous efforts have been devoted to the composition and crystallization engineering in Cs x FA 1– x Pb(I y Br 1– y ) 3 for the development of wide‐bandgap perovskite solar cells. [ 40–54 ]…”

F-Type Pseudo-Halide Anions for High-Efficiency and Stable Wide-Band-Gap Inverted Perovskite Solar Cells with Fill Factor Exceeding 84%

“…As shown in Figure c, the J SC calculated by external quantum efficiency (EQE) is basically the same as the actual measured J SC , and the error is within 5%. In addition, Figure d shows the stable output of the PCE and J SC of devices without and with F-type pseudo-halogen additives under continuous illumination at the maximum power point (MPP) for more than 500 s. Figure e–g and Table S5 summarize the V OC , FF, and PCE of the reported WBG PSCs with a band gap of 1.63–1.72 eV (the red ball is the data of this work). ,,− ,,,,,− Figure h and i show the stability test of the devices at a temperature of 85 °C and a humidity of 50–60%, respectively. The results show that the stability of the devices with F-type pseudo-halogen additives is much greater than that of the control devices, which suggests that the addition of additives helps to improve the stability of the devices.…”

Ordered Element Distributed C3N Quantum Dots Manipulated Crystallization Kinetics for 2D CsPbI3 Solar Cells with Ultra‐High Performance

“…The optimized film can reduce the trap state level and effectively decrease the trap density, which ensures much-reduced carrier recombination, as demonstrated by the dark J-V measurement and SCLC characterization. [59][60][61] The structure of an electron-only and hole-only device is inserted in Figures S8a-d, Supporting Information, where the trap-state densities (N t ) of the optimized film was reduced to almost two (electron-only) and three times (hole-only) than the reference device. This improvement may be ascribed to good phase distribution and high-quality film establishment because of order structural C 3 N QDs, which leads to suppressed carrier recombination and increased mobility and performance.…”