Designing and developing flexible electronics requires a thorough investigation of the substrates available for the fabrication of devices. Here, we present a practical study on a variety of significant substrates: polyethylene terephthalate (PET), its heat-stabilized (HS) derivative, HS-PET, and polyethylene naphthalate (PEN) plastic insulating films; indium tin oxide (ITO)-coated ITO/PEN and ITO/PET transparent conducting films; rigid ITO/glass and FTO/glass substrates; stainless steel and titanium foils. We put the substrates through a range of tests these actually undergo during device fabrication to determine their optical, mechanical flexibility (under different types of tensile and compressive stress bending with and without a PEDOT:PSS conducting polymer layer), solvent resistance, stability to temperature treatment (conductivity and deformation), and to UV irradiation. We highlight issues and propose solutions to improve substrate response. The results and thresholds\ud extracted reveal limitations and windows of opportunity useful for the designer of flexible optoelectronics in determining manufacturing processes and the final applications under everyday operation

applicable to plastic substrates is urgent. [ 22 ] Recently, we proposed a UV irradiation process on a customized TiO 2 nanoparticle paste for the fabrication of effi cient fl exible dye sensitized solar cells (DSCs). [ 23 ] In this work, we demonstrate how UV irradiation can be successfully employed for developing the very thin TiO 2 mesoporous scaffold in this new type of plastic perovskite solar devices. The electron collecting compact layer is also essential for delivering performing devices as it lowers the carrier recombination probability at the interface between the transparent conductive oxide (TCO) and perovskite layers. The only material utilized on plastic substrates up to now has been ZnO deposited by electrodeposition and spin coating of nanoparticles dispersion. [ 12,16 ] Atomic layer deposition (ALD) has been used for the fabrication of ultrathin, uniform, and conformal layers in several PV technologies. [ 24 ] Thermal ALD was adopted to produce a compact TiO 2 layer on glass perovskite cells, yielding higher device PCE compared to spray pyrolysis or the spin coating of a sol-gel solution. [ 25,26 ] Recently, we explored the benefi t of using plasma assisted ALD applied to fl exible DSCs. [ 27 ] Here we adopt plasma ALD of cyclopentadienyl alkylamido titanium Ti(CpMe)(NMe 2 ) 3 precursor to obtain an effective compact TiO 2 blocking layer on indium tin oxide (ITO)-coated plastic substrates. The plasma approach offers several advantages compared to conventional thermal processes, in particular it enables the deposition of higher quality fi lms, in terms of lower pinhole density, in the range of temperatures compatible with conductive plastic substrates. [ 28 ] This feature plays a key role to ensure high effi ciency in the solid state devices. By incorporation of both the ALD-grown compact layer and the UV-irradiated scaffold in the fabrication process, and using a CH 3 NH 3 PbI 3x Cl x perovskite layer, a doped 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)9,9′spirobifl uorene (Spiro-O-MeTAD) as hole transport material (HTM), and a gold top contact, we obtain a PCE of 8.4% for a fl exible plastic cell. This also represents the fi rst example of low temperature and solution processed TiO 2 scaffold for perovskite solar cell either on glass or plastic. Furthermore, we developed a screen printable mesoporous formulation for the scaffold and patterning procedures compatible with the delicate plastic/ITO substrates (based on masking, laser defi nition and self-patterning) for the other layers enabling us to manufacture the fi rst large-area (8 cm 2 ) integrated fl exible perovskite photovoltaic module composed of 4 series-connected cells (PCE of 3.1% over the module and 4.3% over the its best cell).Recently, research on hybrid organometal halide perovskites for photovoltaic applications has delivered impressive growth in power conversion effi ciencies (PCEs) with a current certifi ed record of 17.9% and growing. [1][2][3][4][5][6] Key advantages of perovskites devices, together with high PCEs, are re...

This manuscript reviews the application of atomic layer deposition (ALD) for perovskite solar cells exploring also novel opportunities and the challenges that research has to face to deposit ALD layers on perovskite films.

Flexible Dye Solar Cells (FDSCs), in their most widespread architecture, are assembled with two opposing planar films or foil substrates in metal–plastic or plastic–plastic combinations. The use of one metal electrode enables the convenient utilization of materials and high temperature processes but is accompanied by issues including partial opacity of the electrolyte and catalyst layer. Constraints on the stability of plastic substrates have led to the development of a variety of alternative material formulations and processes to guarantee performance even at low temperatures compatible with plastic films. Recently, efforts in doing without transparent conducting oxides have led to the development of new unconventional architectures. Review of the operation of DSCs shows that initial target markets are represented by indoor applications where power output densities have been shown to outperform competing flexible photovoltaic technologies. Whereas performance, stability in particular, needs to be significantly improved for the adoption in long term outdoor installations, commercial products integrating FDCSs for indoor or portable use have already been launched. Issues pertaining progress in materials, processes, devices and industrialization of FDSCs will be analyzed and discussed in this review