Illumination Enhanced Crystallization and Defect Passivation for High Performance CsPbI₃ Perovskite Solar Cells by Sacrificing Dye

Abstract

All‐inorganic perovskite solar cells (PSCs) have been the research focus due to their high thermal stability and proper band gap for tandem solar cells. However, their power conversion efficiency (PCE) is still lower than that of organic‐inorganic hybrid PSCs. Herein, a sacrificing dye (Rhodamine B isothiocyanate, RBITC) is developed to regulate the growth of perovskite film by in situ release of ethylammonium cations, isothiocyanate anions and benzoic acid molecules upon annealing and illumination. The ethylammonium cations can efficiently passivate surface defects. The isothiocyanate anions incorporate with uncoordinated Pb to regulate the crystallization process. The benzoic acid molecules facilitate the nucleation of the perovskite crystals. Especially, the illumination can accelerate the release of these beneficial ions/molecules to improve the quality of perovskite films further. After optimization with RBITC, a high open circuit voltage (VOC) of 1.24 V and a champion PCE of 20.95% are obtained, which are among the highest Voc and PCE values of CsPbI3 PSCs. Accordingly, the operational stability of the PSC devices is significantly improved. The results provide an efficient chemical strategy to regulate the formation of perovskite films in whole crystallization process for high performance all‐inorganic PSCs.

Crystallization Regulation by Self‐Assembling Liquid Crystal Template Enables Efficient and Stable Perovskite Solar Cells

“…In comparison, the R s and R rec values for the ILC‐modified device are 25.85 and 2142.00 Ω, respectively. The increased R rec and decreased R s demonstrate a lower carrier recombination rate and better carrier transport in the ILC‐modified PSC [58] …”

Novel Strategy for High Efficient and Stable Perovskite Solar Cells through Atomic Layer Deposition

“…The correlation between voltage and light intensity is usually used to estimate the carrier recombination in PSC. 48 Figure 7b displays that the ideal factor decreases from 2.56 to 1.61 kT/q, implying that the B 2 O 3 treatment effectively restrains charge recombination. Besides, TPC and TPV measurements were performed to obtain the charge transport time (τ t ) and recombination time (τ rec ), respectively.…”

“…Compared with the control device, the BOP-based device has a larger recombination resistance, manifesting that the introduction of B 2 O 3 reduces the charge recombination at the interface between perovskite and HTL. The correlation between voltage and light intensity is usually used to estimate the carrier recombination in PSC Figure b displays that the ideal factor decreases from 2.56 to 1.61 kT/q, implying that the B 2 O 3 treatment effectively restrains charge recombination.…”

21.41%‐Efficiency CsPbI3 Perovskite Solar Cells Enabled by an Effective Redox Strategy with 4‐Fluorobenzothiohydrazide in Precursor Solution

“…For passivating and reducing the iodine-related defects, many strategies, such as top-surface modification/reconstruction engineering, [20][21][22] buried bi-interface modification engineering, [9,23,24] and precursor solution engineering, [25][26][27] are adopted. Among them, precursor solution engineering by employing organic matrixes (ammonium salts, [28][29][30] neutral molecules, [7,31,32] zwitterionic molecules, [33,34] etc.)…”

“…Inorganic alkalines are also efficient additives (such as NaOH, KOH, NaHCO 3 ) for perovskite precursor solution engineering, which can regulate iodine-related defects because the disproportionation reaction can take place between I 2 and alkaline in the precursor solution. [35] Compared with inorganic alkaline additives, organic materials with reductive hydrazine (-NHNH 2 ) group can effectively reduce I 2 defect back to I − by a redox reaction and thus to suppress the oxidation of I − anions, such as hydrazine chloride (HACl), [36] 3,5-difluorobenzoic acid hydrazide (FBJ), [37] phenylhydrazinium iodide (PHAI), [38] benzoyl hydrazine (BH), [25] 3-hydrazinobenzoic acid (3-HBA), [39] benzylhydrazine hydrochloride (BHC), [40] and carbohydrazide. [41] Most of the above reductive materials take normal redox reaction between the -NHNH 2 group and I 2 to release N 2 gas and by-products, which either volatilize during the thermalannealing process for fabricating perovskite film or stay to further passivate Pb-related defects by the remained functional groups.…”