PEDOT:PSS (PH, PH1000, AI4083) and their mixtures (PH:PH1000, PH:AI4083, PH:PH1000:AI4083; in 1 : 1 ratios) were used as hole transport layers. Surface properties of these layers have impacted the crystal quality of MAPbI_3−xCl_x and associated device efficiency differently.

With the latest prominent rise in the development of organic solar cells (OSCs), there is a continuous influx of interested students in the OSC research and development field.¹ Lately, researchers have been fascinated mainly by novel non-fullerene acceptors (NFAs) combined with high-performing mid-bandgap polymers.^2,3 However, poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C61 (PCBM) blend is one of the most-studied photoactive layers in OSCs.^{4 – 9} According to Wantz et al.,¹⁰ a remarkable number of papers were published between 2002 and 2010. After a decade, there is still interest in P3HT:PCBM-based devices due to their novel properties and useful aspects compared to NFA-based solar cells.^{11 – 13} Due to the polymers versatile properties, many organic materials have been developed for photovoltaic applications over the last 20 years of applications.^{14 – 17} With the development of novel NFAs that match well with the old P3HT, efficiencies in the range of 10% and beyond are within sight. One of the greatest benefits that P3HT offers over the novel mid-bandgap polymers is that it can be synthesized with a high yield at relatively low costs. Generally speaking, the more complex the synthesis, the higher the associated costs, making it very hard to reach the same economics as with P3HT production.¹⁸ In addition, NFAs that are tailor-made for P3HT nicely complement its limited absorption range and may thus be the perfect partner for P3HT. Moreover, there is still ongoing research for materials that can boost P3HT-based OSCs over the 10% efficiency limit. Despite significant advancements concerning OSC power conversion efficiency (PCE) over the past decade, there is still an ongoing debate over the physical processes restraining the device performance.^19,20

The use of organic halide salts to passivate metal halide perovskite (MHP) surface defects has been studied extensively. Passivating the surface defects of the MHP is of critical importance for realizing highly efficient and stable perovskite solar cells (PSCs). Here, the successful application of a multifunctional organic salt, methyltriphenylphosphonium iodide (MTPPI), used as a passivation additive for grain boundary defects and as a molecular sealing layer in terms of stabilization, has been used to stabilize the mixed cation perovskite RbCsMAFA-PbIBr. To assess the passivating and stabilizing effects of MTPPI on RbCsMAFA-PbIBr PSCs, maximum power point tracking (MPPT) was applied as the most realistic and closest-to-application condition for the ageing test. Here, perovskite solar cells were aged under a light source yielding an excitation intensity corresponding to one sun with maximum power point tracking, which was interrupted periodically by current–voltage sweeps. This allowed for the extraction of all photovoltaic parameters necessary for a proper understanding of the ageing process. The MTPPI additive can donate iodine anions to halide vacancies and compensate a negative surface excess charge with cation interactions. On top of this, the large and bulky methyltriphenylphosphonium (MTPP⁺) cation may block both the escape of volatile perovskite components and the ingress of oxygen and water vapour. These collective roles of MTPPI have improved both the efficiency and stability of the solar cells compared to the reference without passivation additives.

Herein, a simple, low‐cost, solution‐processed, and parallel fabrication method to form metal halide perovskite (MHP) poly and single‐crystalline films confined in ordered micrometer‐sized domains is reported. A cross‐linked polydimethylsiloxane (PDMS) stamp featuring 25 µm side squares is used to pattern their substrates. The substrate is microcontact printed on the PDMS inked with self‐assembled monolayers (SAMs) of alkanethiol to form a molecular template, resulting in hydrophilic (gold) and hydrophobic (alkanethiol) domains. The subsequent deposition of lead bromide (PbBr₂) and methylammonium bromide (MABr) precursor solutions on the pre‐patterned substrate resulted in poly and single‐crystalline films of methylammonium lead bromide (MAPbBr₃) confined to the hydrophilic domains. Two deposition methods: drop‐casting and two‐step spin‐coating are systematically investigated to find well confined and large‐sized single‐crystal MAPbBr₃. Casting proves to be more effective than two‐step spin‐coating to achieve better confinement of MAPbBr₃. The patterning process is monitored in dependence of the a) deposition methods used to b) precisely control the MAPbBr₃ crystal growth in a pre‐defined site which leads to c) grow poly and single‐crystals in a periodic arrangement. Their nondestructive and less energy processable fabrication method will have its own contribution in transferring patterns to desired substrates that enables them to fabricate different types of MHP optoelectronic devices and integrated electronic systems with more complex architectures.