Dopamine Hydrochloride-Assisted Synergistic Modulation of Perovskite Crystallization and Sn²⁺ Oxidation for Efficient and Stable Lead-free Solar Cells

Abstract

Tin perovskites have received great concern in solar cell research owing to their favorable optoelectronic performance and environmental friendliness. However, due to their poor crystallization and easy oxidation, the performance improvement for tin-based perovskite solar cells (TPSCs) is rather challenging. Herein, reductive 3-hydroxytyramine hydrochloride (DACl) with NH2·HCl and phenol groups as co-additives with SnF2 is added into the precursor to modulate perovskite crystallization and inhibit Sn2+ oxidation for high-performance TPSCs. The Lewis base group of NH2 HCl in DACl could bind to perovskite lattices to modulate the crystallization with suppressed defects in the bulk and grain boundary, whereas reductive phenol groups effectively constrain the Sn2+ oxidation. Moreover, the undissociated DACl decreases the supersaturated concentration of tin perovskite solution and creates a pre-nucleation site for rapid nucleation to further regulate crystallization. Consequently, the DACl-derived TPSCs achieve a high power-conversion efficiency (PCE) that reaches up to 11%. More impressively, the device remains at 84% of the initial PCE after full-sun illumination in N2 over 600 h without being encapsulated. This DACl-based synergistic modulation of a lead-free perovskite demonstrates a feasible approach using one molecule with different functional groups to manipulate crystallization, Sn2+ oxidation, and defect reparation of tin perovskite films, providing a critical guideline for constructing high-quality perovskites by multifunctional additives with high photovoltaic performance.

Origins and Suppression of Sn(II)/Sn(IV) Oxidation in Tin Halide Perovskite Solar Cells

“…[56] In summary, these additive as the most used strategy in TP-SCs could be classified into four categories: Sn(II) source additives, reducing agents, Lewis base small molecules, and other additives. They can effectively inhibit Sn(II)/Sn(IV) oxidation in TPSCs before, during, and even after tin perovskite formation: i) enhance the defect formation energy of tin vacancies; [20,86,98] ii) reduce the already oxidized Sn(IV); [23,93,97] iii) enhancing the difficulty of Sn(II)/Sn(IV) oxidation by acid-base coordination or hydrogen bonding with SnI 2 ; [104][105][106][107] iv) additive as a protective layer at the interface of perovskite grains; [100,101,108] v) changing the adsorption energy between the perovskite film and oxygen; vi) changing the oxidation path. [56,76]…”

“…Copyright 2017, American Chemical Society. d) Small Lewis base molecules that can coordinate with Sn 2+ in tin perovskite precursor [21,69,98,[100][101][102][105][106][107]. e) Schematic illustration of silver doping reducing perovskite-oxygen interaction forces.…”

Mutually Tuned Dual Additive Engineering Synergistically Enhances the Photovoltaic Performance of Tin-Based Perovskite Solar Cells

“…The lower hysteresis further confirms the reduced N t and suppressed charge recombination in the perovskite film by additive engineering, which is consistent with the results of Figures (l) and (a–e). The suppressed hysteresis behavior may also be attributed to the intricate interplay of the perovskite and additives . These findings may have potential implications for enhancing device stability …”

“…The suppressed hysteresis behavior may also be attributed to the intricate interplay of the perovskite and additives. 62 These findings may have potential implications for enhancing device stability. 63 Figure 3(c) shows the external quantum efficiencies (EQE) and integral current densities of four T-PSCs, which match well with the J−V results.…”

Ionic Liquid-Mediated Intermediate Phase Adduct Constructing for Highly Stable Lead-Free Perovskite Solar Cells

“…Among various lead-free perovskites, tin perovskites are very promising, with PCEs increasing from 6.4% to 14.8%. , However, the fast crystallization of tin perovskites leads to poor film quality with highly formed defects . Also, the easy oxidation of Sn 2+ in tin perovskites induces p-type doping, leading to nonradioactive recombination loss and poor device performance. − As a result, tin-based perovskite solar cells (TPSCs) possess significantly inferior stability than lead-based PSCs . To overcome these issues, tremendous efforts have been devoted to obtaining high-performance TPSCs via solvent engineering, perovskite composition adjustment, use of additives, and dimensional manipulation, among others. − …”