Cationic and Anionic Vacancy Healing for Suppressed Halide Exchange and Phase Segregation in Perovskite Solar Cells

Abstract

All-inorganic wide-bandgap (WBG) perovskite solar cells are best suited as the top cells for tandem devices. However, they suffer from photoinduced halide segregation (PIHS) and a quick anion exchange reaction (AER). Herein, polyvinylpyrrolidone (PVP) polymer-assisted in situ crystalization of CsPbBr3 and CsPbBr1.5I1.5 compounds is shown to suppress these effects by passivation of both positively charged (halide vacancy) and negatively charged (cation vacancy) defects. Modifying the perovskite precursor solution with this polymer improved the chemical stability and photostability in both nanocrystal solution and solution-processed films. Ultrafast transient absorption measurements elucidate the excited state dynamics of PVP-modified perovskite and probe an improved lifetime of charge carriers. As a proof of concept, PVP-modified CsPbI1.5Br1.5 retained nearly 98% V oc and 90% PCE under 1 sun AM 1.5G illumination for 12 h, while the control devices lost 25% of their V oc within 6 h. Using simple polymer additives to protect WBG perovskites is a huge step toward new device architectures involving all-perovskite heterojunctions.

Perovskite Quantum Dot Solar Cells: Current Status and Future Outlook

“…There are several selection criteria for selecting the shell materials, including (1) lattice match with PQDs for epitaxial growth; (2) suitable band alignment with PQDs that facilitates the charge transport; and (3) stable characteristics to protect PQD cores against ambient stimuli like heat, light, moisture, and oxygen. Shelling PQDs with polymers or metal–organic frameworks (MOF) is a good strategy because the soft structure of the shell materials bring not much difficulty for epitaxial growth, and the development of conductive MOF provides opportunities for band alignment between PQDs and MOF. Besides, the chalcogenide perovskites, sharing a similar crystal structure with PQDs, possess outstanding charge mobility and stability, making them promising candidates as a suitable shelling material for PQDs .…”

Enhanced Perovskite Photovoltaics with Non-conjugated Polymers: Recent Developments and Future Prospects

“…The device also demonstrated rapid recovery upon removal from a wet environment. Pasha et al utilized PVP polymer to facilitate the in situ crystallization of CsPbBr 3 and CsPbBr 1.5 I 1.5 . The study demonstrated that these compounds could mitigate the effects by passivating positively charged (halide vacancy) and negatively charged (cation vacancy) defects.…”

Prevention of ion migration in lead halide perovskites upon plugging the anion vacancies with PbSe islands

“…36 Kamat and coworkers employed PbSO 4 -oleate capping on perovskite, which effectively inhibits ion exchange. 37 Balakrishna's group inhibited the halide ion exchange in tandem devices via passivating the perovskite's defects using polyvinylpyrrolidone 38 while Santra's group prevented the ion migration at the interfaces of CsPbBr 3 –CsPbI 3 using an ultrathin alumina shell. 39 In this context, utilizing metal chalcogenides for plugging halide vacancies can serve as a potential strategy to prevent the migration of halide ions due to the highly covalent nature of the Pb–chalcogen bond that renders it stable.…”