Efficient and Stable Tin Perovskite Solar Cells by Pyridine‐Functionalized Fullerene with Reduced Interfacial Energy Loss

Abstract

In tin perovskite solar cells (PSCs), fullerene (C 60 ) and fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are commonly utilized electron transport materials. However, the energetic disorder, inadequate passivation, and energy level mismatch of C 60 and PCBM limit the improvement of power conversion efficiency (PCE) and lifespan of tin PSCs. In this work, a multifunctional interface manipulation strategy is developed by introducing a pyridine-functionalized fullerene derivative, fullerene-n-butyl-pyridine (C 60 -BPy), into the interface between the tin perovskite and the electron transport layer (ETL) to improve the photovoltaic performance and stability of tin PSCs. The C 60 -BPy can strongly anchor on the perovskite surface via coordination interactions between the pyridine moiety and the Sn 2+ ion, which not only reinforces the passivation of the trap-state within the tin perovskite film, but also regulates the interface energy level alignment to reduce non-radiative recombination. Moreover, the improved interface binding and carrier transport properties of C 60 -BPy contribute to superior device stability. The resulting devices have achieved the highest PCE of 14.14% with negligible hysteresis, and are maintained over 95% of their initial PCE under continuous one-sun illumination for 1000 h.

Direct Observation of Intragrain Defect Elimination in FAPbI3 Perovskite Solar Cells by Two-Dimensional PEA2PbI4

“…The Urbach energy further decreases to 37 meV when PEA 2 PbI 4 and MACl are added together. The Urbach energy is considered to be a reflection of the energetic disorder at the band edge, 50,51 indicating that the "PEA 2 PbI 4 +MACl" films show the lowest band edge energy disorder and trap density. We tested the stability of our devices in ambient air conditions (25 °C and 30 ± 10% relative humidity, in the dark) as shown in Figure 5A.…”

Surface Reconstruction for Tin-Based Perovskite Solar Cells

“…On the other hand, owing to the self-p-type doping characteristics caused by Sn­(II) oxidation-induced high-density V Sn of the Sn-based perovskite layer, the large conduction band offset existing at the contact interface of the perovskite/electron extraction layer (ETL) contributes to serious nonradiative recombination and inefficient electron transport, thereby deteriorating the V oc and fill factor of devices. ,− For lead-based PSCs, many efforts have been made to address the charge extraction and transport issue, among which constructing gradient band alignment within the perovskite has been proven to be an effective strategy. − For example, Kanda et al employed perhydropoly­(silazane) derived silica to modulate the Fermi level of the perovskite surface and induced band-bending from the bulk to surface within perovskite films, thereby facilitating hole extraction and diminishing the V oc deficit . Getting experience from the rapid development of lead-based PSCs, turning attention from bulk optimization to surface engineering is a promising route to attenuate the nonradiative recombination, optimize interfacial band alignment, and suppress surface-activated corrosion of Sn-based PSCs.…”

Prospects for Tin-Containing Halide Perovskite Photovoltaics

“… 152 One approach to mitigate this is using an interlayer inserted between the perovskite and the C 60 layer to avoid their direct contact and suppress interfacial losses. For example, fullerene derivatives, such as C 60 pyrrolidine tris-acid (CPTA) 127 and fullerene- n -butyl-pyridine, 153 would reduce the interfacial recombination caused by the C 60 ETL, thanks to their apparent ability to bind to undercoordinated metal centers while maintaining efficient electron transport. Accordingly, for maximizing the efficacy of the inserted interlayer, both passivation and carrier transporting characteristics may be the criteria that need to be fulfilled.…”