Polarized Ferroelectric Polymers for High‐Performance Perovskite Solar Cells

Abstract

as electric defects, [7,8] charge trapping, [9,10] ion migration, [11,12] and charge accumulation [13,14] are yet to be properly elucidated. These aforementioned issues are strongly associated with the low build-in field (BIF) for charge separation and transporting, bad interface matching, and poor crystallization of perovskite films. Generally, in a photovoltaic device, BIF is the main force to guide the carriers to drift toward corresponding electrodes to avoid recombination. A small BIF will make the carriers be either captured in the trap states or accumulated at the interfaces due to the insufficient driving force provided. Actually, the BIF in the device is normally too small to provide sufficient force to separate charges and transport them, thus resulting in nonradiative recombination of charges or charge-transfer excitons. [15,16] Energy loss (E loss ) is also easily caused by nonradiative recombination of charge carriers in absorber layer and at interfaces. Although the E loss in perovskite solar cells is lower than other photovoltaic technologies except crystalline silicon cells, [17] an E loss as small as possible is desired to realize high-performance PSCs. Meanwhile, the low-quality perovskite crystals significantly limit their optoelectronic properties and thus device performance. [18,19] Defects and trap states generated by difficultto-control nucleation and crystal growth in solution-processed perovskite film will cause a large energy loss in the device. [20,21] Additionally, there is a need to reduce current hysteresis that could cause inaccurate estimation of device efficiency. [22][23][24] Various methods such as film processing, [25,26] additive, [27,28] doping, [29][30][31] and interface abduction [32] have been used to improve the crystalline quality of perovskite films through the modification of the nucleation and growth process. However, few effective methods are reported to enhance BIF with a purpose to improve the carrier's separation and transport. A relevant approach recently reported is the application of an external electric field (EEF) to the photoactive layer in photovoltaic devices to enhance BIF and suppress carrier recombination at trap sites. [33][34][35] And the vertical polarization induced by an EEF could contribute a preferred in-plane stacking mode for perovskite crystals to grow along the out-plane direction. [35] Unfortunately, the polarization by only an EEF is not stable since it is easily screened by the ion migration or accumulation after storing for In hybrid organic-inorganic lead halide perovskite solar cells, the energy loss is strongly associated with nonradiative recombination in the perovskite layer and at the cell interfaces. Here, a simple but effective strategy is developed to improve the cell performance of perovskite solar cells via the combination of internal doping by a ferroelectric polymer and external control by an electric field. A group of polarized ferroelectric (PFE) polymers are doped into the methylammonium lead iodide (MAPbI 3 ) layer and/or...

Lycopene‐Based Bionic Membrane for Stable Perovskite Photovoltaics

“…Perovskite (PVSK) materials possess the advantages of good light absorption, ambipolar charge transport, high defect tolerance, and solution processability. [3][4][5][6][7][8] Nevertheless, the defects and traps in PVSK films limit their device performance by causing non-radiative recombination and ion migration. [9][10][11][12] Most importantly, the dangling bonds at the grain boundaries and film interfaces can easily interact www.afm-journal.de www.advancedsciencenews.com…”

Polymer Additives for Morphology Control in High‐Performance Lead‐Reduced Perovskite Solar Cells

“…Nevertheless, excessive replacement of Pb 2+ by Ba 2+ may result in unstable perovskite structure and lead to inferior photovoltaic properties and poor morphology. To solve this problem, polymer additives, including poly(vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)], polymethyl methacrylate (PMMA), and PEG, were added into the lead‐reduced mixed‐cation perovskite to modify the perovskite films.…”

Emergence of Ferroelectricity in Halide Perovskites

“…integrated P(VDF-TrFE), a ferroelectric polymer, into the light absorption layer of MAPbI 3 and/or between MAPbI 3 and the hole-transporting layer of Spiro-OMeTAD [60]. Thesecomposite materials effectively improve the crystallization of MAPbI 3 , enhance the built-in electric field (E bi ) and decrease the nonradiative recombination of electron-hole pairs in perovskite solar cells.…”