Reconstructing the amorphous and defective surface for efficient and stable perovskite solar cells

Abstract

The surfaces of perovskite solar cells (PSCs) are significant in determining the devices' efficiencies and stabilities. Here, we first uncover that the 4-tert-butylpyridine (tBP), as an essential additive in hole transport layers (HTLs), could recrystallize the amorphous and defective perovskite surface layers and passivate the defective sites on grain surfaces. The reconstruction induces a larger surface work function and mitigates the interface energy level misalignment between perovskite and HTLs, enlarging the photovoltage of the device. Then, we engineer the chemical bonding strength and develop a more effective HTL additive 4-tert-butylpiperidine (tBPp), which possesses a stronger interaction with perovskite surface defective sites than tBP. With the enhanced adsorption, the tBPp-reconstructed perovskite surface exhibits lower densities of defects and better stability under the stimuli of heat, light and humidity. As a result, the optimized tBPp PSC reaches a champion efficiency of 24.2% with much better operation stability. Tracked at the maximum power point under a continuous bias, the unsealed devices in a N 2 atmosphere can nearly maintain their initial efficiency after continuous light exposure for over 1200 h. Our findings provide an underlying understanding of the HTL additives, which markedly affect the efficiency and stability of n-i-p PSCs.

A Single‐Step Cleaning Process for Simultaneous Removal of Surface Impurities and Passivation of Sub‐Surface Defects in Perovskite Solar Cells

“…As a result, they act as trapping centers for photoexcited carriers and pathways for ion migration. [17,18] This significantly impacts the efficiency and stability of the device and thus demands significant attention. Furthermore, the majority of research in chemical cleaning employs a two-step or even multi-step approach involving pre-reaction and subsequent cleaning.…”

Inhibition of defect-induced α-to-δ phase transition for efficient and stable formamidinium perovskite solar cells

“…Consequently, surface/grain boundary passivation is required to stabilize the black-phase FAPbI 3 18 . Many strategies of defects passivation, including introducing low dimensional perovskite, Lewis acid/base molecules and ammonium halide salts etc., have achieved great progress for the formamidinium PSCs 19 – 22 . To date, almost all studies focus on the role of various defects in determining the optoelectronic properties, such as carrier recombination, diffusion lengths and energy band structure in solar cells 22 – 24 .…”

“…Many strategies of defects passivation, including introducing low dimensional perovskite, Lewis acid/base molecules and ammonium halide salts etc., have achieved great progress for the formamidinium PSCs 19 – 22 . To date, almost all studies focus on the role of various defects in determining the optoelectronic properties, such as carrier recombination, diffusion lengths and energy band structure in solar cells 22 – 24 . Such as using density functional theory (DFT), the formation energies and trap level of various defects are theoretically predicted, which has been widely used to guide the practical passivation design 20 , 25 , 26 .…”

Inhibition of defect-induced α-to-δ phase transition for efficient and stable formamidinium perovskite solar cells

“…Consequently, surface/grain boundary passivation is required to stabilize the black-phase FAPbI 3 18 . Many strategies of defects passivation, including introducing low dimensional perovskite, Lewis acid/base molecules and ammonium halide salts et al, have achieved great progress for the formamidinium PSCs [19][20][21][22] . To date, almost all studies focus on the role of various defects in determining the optoelectronic properties, such as carrier recombination, diffusion lengths and energy band structure in solar cells [22][23][24] .…”

“…Many strategies of defects passivation, including introducing low dimensional perovskite, Lewis acid/base molecules and ammonium halide salts et al, have achieved great progress for the formamidinium PSCs [19][20][21][22] . To date, almost all studies focus on the role of various defects in determining the optoelectronic properties, such as carrier recombination, diffusion lengths and energy band structure in solar cells [22][23][24] . Such as using density functional theory (DFT), the formation energies and trap level of various defects are theoretically predicted, which has been widely used to guide the practical passivation design [25][26][27] .…”