A Bifunctional Lewis Base Additive for Microscopic Homogeneity in Perovskite Solar Cells

Abstract

Here, Yang and colleagues introduce an approach to simultaneously controlling grain growth and passivating grain boundaries in perovskite films. The addition of a Lewis base additive to a perovskite precursor solution results in significant enhancement of grain size and reduction in defect density. The additive increases the activation energy to slow down crystal growth and subsequently precipitate at the grain boundary to passivate defects.

Low-temperature, simple and efficient preparation of perovskite solar cells using Lewis bases urea and thiourea as additives: stimulating large grain growth and providing a PCE up to 18.8%

“…1- 6 The quality of perovskites can be improved by solvent annealing, thermal treatment, 7,8 or using additives [9][10][11] to alter the morphology of the perovskites. In recent reports, the PCEs can reach a maximum of 22.7%.…”

“…32 Yang and coworkers rst used urea and thiourea as additives for CH 3 -NH 3 (MA)PbI 3 derived normal (ITO/TiO 2 ) PSCs, and demonstrated a PCE of 18.25% using an annealing temperature of 100 C. 10 Meng et al used DMSO/urea to increase the PCE of normal devices up to 20.06% with the perovskites (FAPbI 3 ) 0.75 (MAPbI 3 ) 0.17 (MAPbBr 3 ) 0.08 and urea derived antisolvent washing process. 33 Considering the complexity of perovskite compositions and the myriad fabricating parameters involved in the previous process, we explored the urea and thiourea as simple precursor additives for inverted (MAPbI 3Àx -Cl x and MAPbI 3 ) PSCs.…”

Highly Efficient and Stable Inverted Perovskite Solar Cell Obtained via Treatment by Semiconducting Chemical Additive

“…[4] Large-sized, highly crystallized, and preferentially oriented perovskite grains provide good surface coverage and a small grain boundary area, which effectively minimize not only the presence of pinholes but also the trapping and recombination of charge carriers. [6] Among the various approaches for increasing the perovskite grain size, the addition of chemical additives, such as hypophosphorous acid, [7] methylammonium chloride, [8] 1,8-diiodooctane, [9] urea, [10] and lead thiocyanate (Pb(SCN) 2 ), [11] is widely adopted as it can exploit simple low-temperature processes (typically <150 °C) desirable for effective continuous processing. [6] Among the various approaches for increasing the perovskite grain size, the addition of chemical additives, such as hypophosphorous acid, [7] methylammonium chloride, [8] 1,8-diiodooctane, [9] urea, [10] and lead thiocyanate (Pb(SCN) 2 ), [11] is widely adopted as it can exploit simple low-temperature processes (typically <150 °C) desirable for effective continuous processing.…”

“…[10] They argued that the Lewis acid-base interaction between the perovskite precursors and the urea might increase the critical Gibbs free energy of nucleation, which decreases the number of nuclei formed. [10] They argued that the Lewis acid-base interaction between the perovskite precursors and the urea might increase the critical Gibbs free energy of nucleation, which decreases the number of nuclei formed.…”

“…In particular, organicinorganic hybrid perovskite solar cells (PeSCs), which exhibit remarkable power conversion efficiencies (PCEs) exceeding 22% [1] and unique optoelectronic properties, [1c,2] have attracted considerable interest as the most promising materials for large-scale solar energy conversion. [6] Among the various approaches for increasing the perovskite grain size, the addition of chemical additives, such as hypophosphorous acid, [7] methylammonium chloride, [8] 1,8-diiodooctane, [9] urea, [10] and lead thiocyanate (Pb(SCN) 2 ), [11] is widely adopted as it can exploit simple low-temperature processes (typically <150 °C) desirable for effective continuous processing. [4] Large-sized, highly crystallized, and preferentially oriented perovskite grains provide good surface coverage and a small grain boundary area, which effectively minimize not only the presence of pinholes but also the trapping and recombination of charge carriers.…”