Grain Enlargement and Defect Passivation with Melamine Additives for High Efficiency and Stable CsPbBr₃ Perovskite Solar Cells

Abstract

The preparation of high‐quality perovskite films with low grain boundaries and defect states is a prerequisite for achieving high‐efficiency perovskite solar cells (PSCs) with good environmental stability. An effective additive engineering strategy has been developed for simultaneous defect passivation and crystal growth of CsPbBr3 perovskite films by introducing 1,3,5‐triazine‐2,4,6‐triamine (melamine) into the PbBr2 precursor solution. The resultant melamine–PbBr2 film has a loose, large‐grained structure and decreased crystallinity, which has a positive effect on the crystallization process of the perovskite as it retards the crystallization rate as a result of the interaction between melamine and lead ions. Additionally, the passivation by melamine gives a high‐quality CsPbBr3 perovskite film with fewer grain boundaries, lower defect densities, and better energy level matching is achieved by multistep liquid‐phase spin‐coating, which greatly suppresses the nonradiative recombination resulting from the defects and promotes charge extraction at the interface. A champion power conversion efficiency as high as 9.65 % with a promising open‐circuit voltage of 1.584 V is achieved for PSCs with an architecture of fluorine‐doped tin oxide/c‐TiO2/m‐TiO2/melamine‐added CsPbBr3/carbon‐based hole‐transporting layer. Furthermore, the unencapsulated melamine‐added CsPbBr3 PSC shows superior thermal and humidity stability in ambient air at 85 °C or 85 % relative humidity over 720 h.

Recent progress in morphology optimization in perovskite solar cell

“…J. Zhu et al used 1,3,5-triazine-2,4,6-triamine (melamine) additive into PbBr 2 precusor solution and fabricated high quality CsPbBr 3 perovskite ms with lower grain boundary. 74 It was observed that a combination formed between lead ions and melamine which produces void free perovskite lm with loose grain size and less defect density. In melamine passivated lms, suppressed recombination of charge carriers was observed due to better energy level matching.…”

All-inorganic CsPbBr3 perovskite: a promising choice for photovoltaics

“…To enhance the quality of perovskite films, a variety of additives including ammonium salts, [169][170], nanoparticles [171], polymers [167], Lewis acid or base [172] Ionic liquids [173][174] and have been employed to the precursor solution to bond with the and halogen ionic defects and uncoordinated Pb 2+ . Previously, Yang et al [175] Zhu and coworkers [177] introduced a commonly available additive melamine in PbBr 2 precursor solution to passivate the defects and simultaneously develop the crystal growth of CsPbBr 3 perovskite films. They find out that crystallinity of PbBr is affectively reduced with the introduction of melamine, and a high quality, pinhole free, and large grain size CsPbBr 3 film is prepared (Fig.19a).…”

The role of carbon-based materials in enhancing the stability of perovskite solar cells

“…175 Therefore, the passivation of these defects is an efficient approach to improve photovoltaic performance and stability. 176 Carbon quantum dots were used as additive in the LHP layer in order to passivate the crystal defects, improve the crystallinity, increase the grain size, reduce the grain boundary, and, in general, prepare high-quality MAPbI 3 films. 177 The unencapsulted devices with carbon quantum dots additive in LHP maintained 85% of their initial PCE after 20 days in air with humidity of 30% (at 20 1C), while the PCE of PSC with pristine LHP decreased by 44%.…”