C₆₀ as an Efficient n-Type Compact Layer in Perovskite Solar Cells

Abstract

Organic-inorganic halide perovskite solar cells have rapidly evolved over the last 3 years. There are still a number of issues and open questions related to the perovskite material, such as the phenomenon of anomalous hysteresis in current-voltage characteristics and long-term stability of the devices. In this work, we focus on the electron selective contact in the perovskite solar cells and physical processes occurring at that heterojunction. We developed efficient devices by replacing the commonly employed TiO2 compact layer with fullerene C60 in a regular n-i-p architecture. Detailed spectroscopic characterization allows us to present further insight into the nature of photocurrent hysteresis and charge extraction limitations arising at the n-type contact in a standard device. Furthermore, we show preliminary stability data of perovskite solar cells under working conditions, suggesting that an n-type organic charge collection layer can increase the long-term performance.

Efficient and Air‐Stable Mixed‐Cation Lead Mixed‐Halide Perovskite Solar Cells with n‐Doped Organic Electron Extraction Layers

“…[21] Organic charge collection layers, such as fullerenes, have been shown to enable highly effective electron extraction when interfaced with the perovskite absorbers [22][23][24] and reduce UV-induced degradation of the solar cell in comparison with devices employing inorganic TiO 2 . [22] The use of organic layers also facilitates fabricating the entire solar cell at low temperatures (no need for the high temperature sintering step required to obtain highly crystalline metal oxide layers), suitable for processing involving temperature sensitive substrates, including flexible plastic foil and for silicon solar cells. [22] However, compared with their inorganic metal oxide counterparts, organic semiconductors are prone to degradation in water, oxygen, and UV light themselves.…”

“…[22] The use of organic layers also facilitates fabricating the entire solar cell at low temperatures (no need for the high temperature sintering step required to obtain highly crystalline metal oxide layers), suitable for processing involving temperature sensitive substrates, including flexible plastic foil and for silicon solar cells. [22] However, compared with their inorganic metal oxide counterparts, organic semiconductors are prone to degradation in water, oxygen, and UV light themselves. [18] One strategy for circumventing this problem with organic charge extraction layers is to utilize air-stable dopants that increase the density of mobile charge to compensate for the trapped charge, which could be generated under operation, i.e., with the presence of O 2 , H 2 O.…”

“…[22,30] Here we therefore focus our efforts on employing C 60 as the n-type charge collection layer. We first investigate the influence of n-doping of the C 60 layer.…”

Enhanced Ambient Stability of Efficient Perovskite Solar Cells by Employing a Modified Fullerene Cathode Interlayer

“…can happen depending on the type and strength of interactions between materials and the order of contact formation between organic and inorganic interfaces 10. Thus far, various interfacial engineering approaches have been applied to PVSCs to promote charge transport and electrode selectivity, such as passivating perovskite/CTL interfaces, introducing cathode buffer interlayer, and doping CTLs 11. Another major challenge in interface engineering is to enhance the ambient stability of PVSCs for long‐term uses.…”

Thermal Precursor Approach to Pristine Fullerene Film as Electron Selective Layer in Perovskite Solar Cells

“…Fullerene-based molecules such as [6,6]phenyl-C 61 -butyric acid methyl ester ([60]PCBM) and pristine C 60 have been used as ESL both in the n-i-p and p-i-n PSC devices. [15][16][17][18][19][20][21][22][23] As an additional merit, the fullerene-based ESLs reduce the density of trap states and passivate the grain boundaries of the CH 3 NH 3 PbI 3 perovskite-absorbing layer, suppressing the hysteresis in the current density-voltage (J-V) curves. 24,25 In comparison with [60]PCBM, the pristine C 60 with no bulky substituents is expected to be packed more densely to facilitate the intermolecular charge transport.…”