On the origin of open-circuit voltage losses in flexible n-i-p perovskite solar cells. Issue 1 (31st December 2019)

• Record Type: Journal Article
• Authors: Pisoni, Stefano; Stolterfoht, Martin; Löckinger, Johannes; Moser, Thierry; Jiang, Yan; Caprioglio, Pietro; Neher, Dieter; Buecheler, Stephan; Tiwari, Ayodhya N.
• Is Part Of: Science and technology of advanced materials. Volume 20:Issue 1(2019)
• Page Start: 786
• Page End: 795
• Publication Date: 2019-12-31
• Subjects: Perovskite solar cell -- flexible -- interface engineering -- non-radiative recombination -- quasi-Fermi level splitting; 50 Energy Materials -- 100 Materials; 201 Electronics / Semiconductor / TCOs -- 206 Energy conversion / transport / storage / recovery -- 209 Solar cell / Photovoltaics -- 212 Surface and interfaces -- 306 Thin film / Coatings; Materials -- Technological innovations -- Periodicals; 620.112
• DOI: 10.1080/14686996.2019.1633952
• Languages: English
• ISSNs: 1468-6996

Abstract

ABSTRACT: The possibility to manufacture perovskite solar cells (PSCs) at low temperatures paves the way to flexible and lightweight photovoltaic (PV) devices manufactured via high-throughput roll-to-roll processes. In order to achieve higher power conversion efficiencies, it is necessary to approach the radiative limit via suppression of non-radiative recombination losses. Herein, we performed a systematic voltage loss analysis for a typical low-temperature processed, flexible PSC in n-i-p configuration using vacuum deposited C60 as electron transport layer (ETL) and two-step hybrid vacuum-solution deposition for CH3 NH3 PbI3 perovskite absorber. We identified the ETL/absorber interface as a bottleneck in relation to non-radiative recombination losses, the quasi-Fermi level splitting (QFLS) decreases from ~1.23 eV for the bare absorber, just ~90 meV below the radiative limit, to ~1.10 eV when C60 is used as ETL. To effectively mitigate these voltage losses, we investigated different interfacial modifications via vacuum deposited interlayers (BCP, B4PyMPM, 3TPYMB, and LiF). An improvement in QFLS of ~30–40 meV is observed after interlayer deposition and confirmed by comparable improvements in the open-circuit voltage after implementation of these interfacial modifications in flexible PSCs. Further investigations on absorber/hole transport layer (HTL) interface point out the detrimental role of dopants in Spiro-OMeTAD film (widely employed HTL in the community) as recombination centers upon oxidation and light exposure. Graphical abstract: uf0001