# Solution Processed Polymer-ABX\({}_{4}\) Perovskite-Like Microcavities
## 1 Introduction  
Hybrid perovskites garnered increasing interest due to the ease of engineering their optoelectronic properties via simple wet chemistry and to the good power conversion efficiencies achieved in photovoltaics [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]. Successively, the solution processability of these materials has opened up new perspectives on abiding costs and simplifying fabrication processes for lightening and optoelectronic devices such as light emitting diodes and solid-state lasers [11; 12; 13; 14; 15; 16; 17; 18], whilst maintaining the ease of tunability of the emission properties. Among these, perovskite-like material with 2D lattices, such as 2,2'-(ethylenedioxy)bis(ethylammonium) lead chloride (EDBE)PbCl\({}_{4}\), became interesting thanks to its broad photoluminescence spectrum, which ranges from the ultraviolet to the near infrared and gives to this material its characteristic broad photoluminescence [19; 20; 21; 22; 23; 24; 25; 26; 27]. These characteristics arise from the 2D structures in which the large organic molecule allows for the formation of a lamellar crystalline structures where planes of lead chloride are alternated to planes of 2,2'-(ethylenedioxy)bis(ethylammonium) [19; 20]. These materials are promising for light-emitting devices coupled to photonic structure to engineer their emission [28; 29; 11; 20]. Photonic crystals have indeed been widely employed to engineer the emissionof photoactive materials [31; 32; 33; 34]. Among the large variety of photonic structures demonstrated in recent decades, spun-cast planar microcavities and distributed Bragg reflectors (DBRs) are a viable and low-cost approach to this task thanks to solution processing and the large availability of polymer media [35]. These structures consist of dielectric lattices made of thin film with different refractive indexes, alternated periodically, that interact with light generating specific frequency regions forbidden photon propagation, namely photonic band gaps (PBGs). Microcavities and DBRs were demonstrated for several applications including photon recycling in photovoltaics [36], sensing [37; 38; 39; 40; 41; 42] and optical switchers [43; 44; 45]. With regards to emission control, these planar lattices are of interest thanks to the spectral and directional redistribution of the photoluminescence oscillator strength [46], as already demonstrated for polymers and organic dyes [47; 48; 49; 50; 51; 52; 53; 54; 55] as well as inorganic emitters [54; 56]. To control emitted light, the photoactive material can be placed within an engineered defect in the planar lattice [47; 49], or it can be used as an active component of the photonic crystal lattice itself [48; 57; 58]. These two strategies favor emission enhancement from the cavity mode or band edge, respectively. Unfortunately, as with most solution-processable perovskites, (EDBE)PbCl\({}_{4}\) can only be casted from broad-spectrum solvents such as dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), which are solvents for most of the commercial polymers, thus making mutual processing of polymer photonic structures and perovskites incompatible. To circumvent these limitations, in a previous work, we coupled white emitting (EDBE)PbCl\({}_{4}\) thin films casted on fused silica or thick polyethylene terephthalate substrates, with DBRs that where successively grown on top of the perovskite layer to create half microcavities able of emission enhancement and suppression [21]. Successively, we were able to embed a perovskite thin film as a cavity layer within a polymer microcavity, achieving a Q factor of 155 and employing perfluorinated protective layers to avoid the dissolution of the underlying polymer photonic structure during the (EDBE)PbCl\({}_{4}\) deposition [59; 60]. In this case, the use of a perfluorinated compound as a protective layer complicated the fabrication processes.