High open circuit voltages in pin-type perovskite solar cells through strontium addition. Issue 2 (21st January 2019)

• Record Type: Journal Article
• Authors: Caprioglio, Pietro; Zu, Fengshuo; Wolff, Christian M.; Márquez Prieto, José A.; Stolterfoht, Martin; Becker, Pascal; Koch, Norbert; Unold, Thomas; Rech, Bernd; Albrecht, Steve; Neher, Dieter
• Is Part Of: Sustainable energy & fuels. Volume 3Issue 2(2019)
• Page Start: 550
• Page End: 563
• Publication Date: 2019-01-21
• Subjects: Renewable energy sources -- Periodicals; Fuel cells -- Periodicals; Electric batteries -- Periodicals; Electrochemistry -- Periodicals; 660.297
• DOI: 10.1039/c8se00509e
• Languages: English
• ISSNs: 2398-4902

Abstract

Abstract : The incorporation of strontium into perovskite solar cells spontaneously modifies the surface increasing the V oc by reducing the non-radiative losses. Abstract : The incorporation of even small amounts of strontium (Sr) into lead-base hybrid quadruple cation perovskite solar cells results in a systematic increase of the open circuit voltage ( V oc ) in pin-type perovskite solar cells. We demonstrate via absolute and transient photoluminescence (PL) experiments how the incorporation of Sr significantly reduces the non-radiative recombination losses in the neat perovskite layer. We show that Sr segregates at the perovskite surface, where it induces important changes of morphology and energetics. Notably, the Sr-enriched surface exhibits a wider band gap and a more n-type character, accompanied with significantly stronger surface band bending. As a result, we observe a significant increase of the quasi-Fermi level splitting in the neat perovskite by reduced surface recombination and more importantly, a strong reduction of losses attributed to non-radiative recombination at the interface to the C60 electron-transporting layer. The resulting solar cells exhibited a V oc of 1.18 V, which could be further improved to nearly 1.23 V through addition of a thin polymer interlayer, reducing the non-radiative voltage loss to only 110 meV. Our work shows that simply adding a small amount of Sr to the precursor solutions induces a beneficial surface modification in the perovskite, without requiring any post treatment, resulting in high efficiency solar cells with power conversion efficiency (PCE) up to 20.3%. Our results demonstrate very high V oc values and efficiencies in Sr-containing quadruple cation perovskite pin-type solar cells and highlight the imperative importance of addressing and minimizing the recombination losses at the interface between perovskite and charge transporting layer.