High‐Performance Flexible Perovskite Solar Cells via Precise Control of Electron Transport Layer

Abstract

Flexible perovskite solar cells (f‐PSCs) have attracted great attention due to their promising commercial prospects. However, the performance of f‐PSCs is generally worse than that of their rigid counterparts. Herein, it is found that the unsatisfactory performance of planar heterojunction (PHJ) f‐PSCs can be attributed to the undesirable morphology of electron transport layer (ETL), which results from the rough surface of the flexible substrate. Precise control over the thickness and morphology of ETL tin dioxide (SnO2) not only reduces the reflectance of the indium tin oxide (ITO) on polyethylene 2,6‐naphthalate (PEN) substrate and enhances photon collection, but also decreases the trap‐state densities of perovskite films and the charge transfer resistance, leading to a great enhancement of device performance. Consequently, the f‐PSCs, with a structure of PEN/ITO/SnO2/perovskite/Spiro‐OMeTAD/Ag, exhibit a power conversion efficiency (PCE) up to 19.51% and a steady output of 19.01%. Furthermore, the f‐PSCs show a robust bending resistance and maintain about 95% of initial PCE after 6000 bending cycles at a bending radius of 8 mm, and they present an outstanding long‐term stability and retain about 90% of the initial performance after >1000 h storage in air (10% relative humidity) without encapsulation.

Stretchable Perovskite Solar Cells with Recoverable Performance

“…[8][9][10][11][12][13] However, printable PSCs based on flexible substrates should reproduce the high performance obtained with rigid devices,w hile simultaneously maintaining excellent mechanical bendable and stretchable stabilities. [14][15][16][17][18][19] Challengingly,perovskite films on flexible substrate are naturally brittle and possess poor crystallinity and numerous grain boundaries. [20][21][22] Theg rain boundary of perovskite has been verified as ac rucial defect that contributes to the efficiencya nd environmental stability loss of PSCs.…”

“…[20,33] Furthermore,some metal oxide interfacial materials have been used to improve the PCE of flexible PSCs with as atisfactory bendability. [15,34,35] However,t he stretchability of flexible PSCs,a sa nother significant touchstone required to meet the requirements of diverse applications,israrely studied. [16,36] Herein, we introduce the self-healing polyurethanes (s-PU), with adynamic covalent oxime-carbamate structure, as as caffold in the perovskite crystallization process.W ith this strategy,the perovskite films with enhanced grain size and improved crystallinity are meniscus-coated (Supporting Information, Figure S1) on the stretchable polydimethylsiloxane (PDMS) substrate.C onsequently,t he flexible PSCs fabricated by the meniscus-coating achieve aPCE of 19.15 % with inconspicuous hysteresis,a sc ompared to the PCE of 14.7 %f or the PSCs without the s-PU additive.B ecause the hydrophobic s-PU elastomer fully fills the grain boundary,the PSCs retain 86 %o ft heir initial efficiency after 3000 hours under 1s un illumination under atmospheric conditions.…”

A Review on Solution‐Processable Dopant‐Free Small Molecules as Hole‐Transporting Materials for Efficient Perovskite Solar Cells

“…Nowadays, all the three types of devices could present a PCE of 23.0% [12] and a 25.2% efficiency has been certified, transcending the values of their competitors including CIGS, CdTe, and multicrystalline silicon-based solar cells, [5] and thus indicating their bright future to be commercially industrialized. [13,14] However, still several obstacles should be surmounted until realizing the industrialization, among which the long-term stability of PSCs is one of the focuses, including the instability of the perovskite layer and the HTL themselves. Since the perovskite material tends to degrade when exposed to humidity, light illumination, [15] oxygen, and high temperature, various scientific endeavors have been devoted to improve its stability apart from the encapsulation of the whole device.…”

Highly Flexible and Transparent Polylactic Acid Composite Electrode for Perovskite Solar Cells

“…Nevertheless, most of the F‐PSCs are fabricated on plastic substrates such as PET, polyethylene naphthalate, or polydimethylsiloxane (organosilicon compound). [ 27–30 ] These substrates will bring tremendous pressure on the environment after expiry. [ 31 ] Moreover, these substrates have relatively poor biocompatibility and bad sensory comfort as a wearable electronic device.…”