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Moving away from the high-performance achievements in organometal halide perovskite (OHP)-based optoelectronic and photovoltaic devices, intriguing features have been reported in that photocarriers and mobile ionic species within OHPs interact with light, electric fields, or a combination of both, which induces both spatial and temporal changes of optoelectronic properties in OHPs. Since it is revealed that the transport of photocarriers and the migration of ionic species are affected not only by each other but also by the inhomogeneous character, which is a consequence of the route selected to deposit OHPs, understanding the nanostructural evolution during OHP deposition, in terms of the resultant structural defects, electronic traps, and nanoscopic charge behaviors, will be valuable. Investigation of the film-growth mechanisms and strategies adopted to realize OHP films with less-defective large grains is of central importance, considering that single-crystalline OHPs have exhibited the most beneficial properties, including carrier lifetimes. Critical factors governing the behavior of photocarriers, mobile ionic species, and nanoscale optoelectronic properties resulting from either or all of them are further summarized, which may potentially limit or broaden the optoelectronic and photovoltaic applications of OHPs. Through inspection of the recent advances, a comprehensive picture and future perspective of OHPs are provided.

Organic-inorganic hybrid perovskite solar cells have emerged as promising candidates for next-generation solar cells. To attain high photovoltaic efficiency, reducing the defects in perovskites is crucial along with a uniform coating of the films. Also, evaluating the quality of synthesized perovskites via facile and adequate methods is important as well. Herein, CHNHPbI perovskites were synthesized by applying second solvent dripping to nonstoichiometric precursors containing excess CHNHI. The resulting perovskite films exhibited a larger average grain size with a better crystallinity compared to that from stoichiometric precursors. As a result, the performance of planar perovskite solar cells was significantly improved, achieving an efficiency of 14.3%. Furthermore, perovskite films were effectively analyzed using a conductive AFM and noise spectroscopy, which have been uncommon in the field of perovskite solar cells. Comparing the topography and photocurrent maps, the variation of photocurrents in nanoscale was systematically investigated, and a linear relationship between the grain size and photocurrent was revealed. Also, noise analyses with a conductive probe enabled examination of the defect density of perovskites at specific grain interiors by excluding the grain-boundary effect, and reduced defects were clearly observed for the perovskites using CHNHI-rich precursors.

Studies of organometallic perovskite solar cells have remarkably progressed within several years, but there still remain concerns of poor stability and insufficient power conversion efficiency (PCE). To overcome these limitations, modification of the perovskite material should be addressed. Herein, imidazole (C3H4N2) is demonstrated as an A‐site solute for the conventional methyl‐ammonium lead iodide (CH3NH3PbI3). As an aromatic hydrocarbon and diamine species with a small ionic radius, imidazole is appropriately alloyed and the bond interactions within the ABX3 lattice are increased. Also, the nature of delocalized π bonding and the unique structure of imidazole allow the formation of an unprecedented kind of hybrid perovskite exhibiting favorable band alignment and optical propertie with high electrical conductivity. Optimal content of imidazole incorporated into CH3NH3PbI3 with architectural optimization of the device leads to improved PCEs approaching 20.2% (reverse) with small hysteresis (forward PCE = 19.0%). Furthermore, properly alloyed imidazole into the A‐site of CH3NH3PbI3 leads to extra stability against air, light, and heat. Lastly, devices with a large active area of 2 cm2 exhibit PCEs as high as 16.8%, further addressing the effect of imidazole on the formation of high quality nanostructured perovskite and devices.