A Multifunctional Fluorinated Polymer Enabling Efficient MAPbI₃-Based Inverted Perovskite Solar Cells

Abstract

Exploring polymeric hole-transporting materials (HTMs) with passivation functions represents a simplified and effective approach to minimize the perovskite defect density. To date, most of reported polymeric HTMs were applied to fabricate n-i-p regular perovskite solar cells (PSCs). The polymers compatible for p-i-n inverted PSCs were very limited. Moreover, the passivation polymers were devoted to passivate the uncoordinated Pb2+. However, the MA+ cation defect has profound unwanted effect on device efficiency and long-term stability. In order to synchronously passivate the Pb2+ and MA+ defects in p-i-n inverted PSCs, a new nonfused polymer was intentionally explored via mild polymerization. The aromatic bridge instead of long alkyl chains enabled polymer BN-12 to achieve excellent thermal stability and good wettability of perovskite precursor. Furthermore, the incorporation of chemical anchor sites (“CO” and “F”) strongly controlled the crystallization of perovskite and restrained the MA+ ion migration. As a result, a significant fill factor (FF) of 82.9% and an enhanced power conversion efficiency (PCE) of 20.28% were achieved for MAPbI3-based devices with the dopant-free BN-12, exceeding those with the commercial HTM PTAA (FF = 81.7%, PCE = 19.51%). More importantly, the unencapsulated devices based on BN-12 realized outstanding long-term stability, maintaining approximately 95% of its initial efficiency after stored for 85 days. By contrast, the PTAA-based device showed rapid decrease which retained only 50% of its initial value after 45 days.

Recent Progresses on Dopant‐Free Organic Hole Transport Materials toward Efficient and Stable Perovskite Solar Cells†

“…In 2022, Xue's group reported a polymeric HTM BN‐12 using MeOTPA as the end group. [ 121 ] Its polyether (ester) backbone contributes to the formation of good molecular freedom and appropriate flexibility, so that the polymer has good film forming ability. In addition, BN‐12 exhibited strong defect passivation ability.…”

Growth mechanism of metal halide perovskite single crystals in solution

“…Initially, this method involved adding supplementary additives to adjust the active layer performance of perovskite solar cells. 67–71 In recent studies, this strategy has also been implemented for the production of large-sized MHP SCs. 65,66,72 Typically, organic macromolecules or polymers with specific functional groups are employed to regulate the nucleation and growth of MHP SCs.…”

“…65,66,72 Typically, organic macromolecules or polymers with specific functional groups are employed to regulate the nucleation and growth of MHP SCs. Examples of such functional groups include the carbon–oxygen bond in polyether (ester)-based molecules and the fluorine ion group, 68 as well as the carbon–nitrogen bond in polymethyl methacrylate-acrylamide and 2-cyanoacrylate. 69,70 These additives are broadly categorized into three groups based on their functional groups: S-donors, O-donors, and N-donors, with varying coordination capabilities.…”

Confinement of MACl guest in 2D ZIF-8 triggers interface and bulk passivation for efficient and UV-stable perovskite solar cells

“…This could induce component stoichiometry imbalance and bulk phase defects. 17,18 Thus, many cation vacancies are left and result in the unfavorable transfer of photogenerated carriers. Therefore, cation vacancy compensation for MA-based perovskite becomes an effective way to enhance device performance.…”