Multistrategy Toward Highly Efficient and Stable CsPbI₂Br Perovskite Solar Cells Based on Dopant‐Free Poly(3‐Hexylthiophene)

Abstract

All‐inorganic perovskites have attracted substantial interest due to their outstanding thermal stability. However, the device performance is still inferior to the typical organic–inorganic counterparts because of the unsatisfying phase stability and defects of the inorganic perovskite films. Herein, a multistrategy to optimize CsPbI2Br perovskite solar cells (PSCs) based on dopant‐free poly(3‐hexylthiophene) (P3HT) by applying thienylmethylamine acetate additive to enhance the α phase stability and passivate the bulk defects of CsPbI2Br perovskite is successfully demonstrated, followed by implementing BTCIC‐4Cl interlayer at CsPbI2Br/P3HT interface, which can coordinate with both perovskite and P3HT to suppress the surface defects and promote the hole transport. Benefitting from these, a champion power conversion efficiency (PCE) of 16.3% is achieved, and the unencapsulated optimized device can retain 97% of the initial PCE after aging under N2 atmosphere at 85 °C for 530 h. This work opens up a new era of multistrategy for improving performance and stability of CsPbI2Br PSCs based on dopant‐free hole transport layer.

Progress and Perspective on Inorganic CsPbI2Br Perovskite Solar Cells

“…The most common one is acetate ion (CH 3 COO − , Ac − ). [39,44,101,116,133] For example, Liu et al [44] demonstrated that Ac − in the halogen site of CsPbI 2 Br could optimize the film morphology and improve crystallinity of CsPbI 2 Br perovskite, thus, reducing the defect concentration and increasing the carrier lifetime of the modified film. Moreover, density functional theory (DFT) calculations showed that Ac − induced a distortion of the perovskite structure along with a deviation of the PbIPb bond angle from the ideal 180° (Figure 7a).…”

“…Other studies have also proved that Ac − induced smaller perovskite grain size, passivated grain boundaries, and stabilized the crystal lattice. [39,101,133] Han et al studied in situ passivation of Ac − in CsPbI 2 Br PSCs. [39] In this work, PbO was formed in situ at the grain boundary by decomposing Pb(Ac) 2 at high annealing temperature.…”

“…In our preliminary work, we employed thienylmethylamine acetate (ThMAAc, Th) additive to enhance α phase stability and passivate the bulk defects of CsPbI 2 Br perovskite film through the interaction between ThMAAc and PbI 2 . [ 133 ] The results showed that ThMAAc could induce the formation of α‐CsPbI 2 Br perovskite, avoiding the non‐photoactive δ‐CsPbI 2 Br perovskite. At the same time, ThMAAc could induce higher crystallization of CsPbI 2 Br perovskite with more uniform grains.…”

Organic Molecules in All‐Inorganic CsPbIxBr3−xPerovskite Solar Cells: Interface Modifiers or Precursor Additives

“…The binding effect between BTCIC‐4Cl and CsPbI 2 Br/P3HT could significantly affect the performance and stability of the device. [ 62 ]…”

Constructing Molecular Bridge for High-Efficiency and Stable Perovskite Solar Cells based on P3HT Hole Transport Material

“…In order to solve this problem, interfacial engineering is widely applied. For example, implementing BTCIC-4Cl 29 or copper(I) thiocyanate (CuSCN) 30 at perovskite/P3HT interface to passivate the surface defects of perovskite can give a reported e ciency of ~ 16% for CsPbI 2 Br-based devices. Seo et al introduced a layer of n-hexyl trimethyl ammonium bromide (HTAB) to modulate the packing of P3HT and obtained a PCE over 22% for (FAPbI 3 ) 0.95 (MAPbBr 3 ) 0.05 -based device 26 .…”