Addressing the toxicity issue in lead-based perovskite compounds by seeking other nontoxic candidate elements represents a promising direction to fabricate lead-free perovskite solar cells. Recently, Cs 2 AgBiBr 6 double perovskite achieved by replacing two Pb 2+ with Ag + and Bi 3+ in the crystal lattice has drawn much attention owing to the convenient substitution of its chemical compositions. Herein, the dependence of the optoelectronic properties and corresponding photovoltaic performance of Cs 2 AgBiBr 6 thin films on the deposition methods of vacuum sublimation and solution processing is investigated. Compared to the vacuum sublimation based one, the solution-processed Cs 2 AgBiBr 6 shows inherently higher crystallinity, narrower electronic bandgap, longer photoexcitation lifetime, and higher mobility. The excellent optoelectronic properties are attributed to the accurate composition stoichiometry of Cs 2 AgBiBr 6 films based on solution processing. These merits enable the corresponding perovskite solar cells to deliver a champion power conversion efficiency (PCE) of 2.51%, which is the highest PCE in the Cs 2 AgBiBr 6based double perovskite solar cells to date. The finding in this work provides a clear clue that a precise composition stoichiometry could guarantee the formation of high quality multicomponent perovskite films.

Solution-processable organometal halide perovskites have been emerging as very promising materials for light-emitting diodes (LEDs) because of their high color purity, low cost, and high photoluminescence quantum yield. However, their electroluminescent performance is still limited by incomplete surface coverage and inefficient charge injection into the perovskite. Here, we demonstrate highly efficient perovskite LEDs (PeLEDs) incorporating full film coverage and bipolar charge injection within the active layer by introducing perovskite precursor poly(9-vinylcarbazole):1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (PVK:TPBi) toluene solution into CHNHPbBr N,N-dimethylformamide solution. Both the film coverage and the charge injections were simultaneously improved by antisolvent of toluene and PVK:TPBi matrix, respectively. After the film morphology and weight ratio of PVK:TPBi were carefully adjusted, the optimal PeLEDs gave efficient emission with turn-on voltage of ∼2.8 V, maximum luminance of ∼7263 cd/m, maximum current efficiency of ∼9.45 cd/A, and maximum external quantum efficiency of ∼2.28%, which are among the best results based on MAPbBr reported to date.

Hole‐transporting materials (HTMs) play a significant role in hole transport and extraction for perovskite solar cells (PeSCs). As an important type of HTMs, the spiro‐architecture‐based material is widely used as small organic HTM in PeSCs with good photovoltaic performances. The skeletal modification of spiro‐based HTMs is a critical way of modifying energy level and hole mobility. Thus, many spiro alternatives are developed to optimize the spiro‐type HTMs. Herein, a novel carbazole‐based single‐spiro‐HTM named SCZF‐5 is designed and prepared for efficient PeSCs. In addition, another single‐spiro HTM SAF‐5 with reported 10‐phenyl‐10H‐spiro[acridine‐9,9′‐fluorene] (SAF) core is also synthesized for comparison. Through varying from SAF core to SCZF core as well as comparing with the classic 9,9′‐spiro‐bifluorene, it is found that the new HTM SCZF‐5 exhibits more impressive power conversion efficiency (PCE) of 20.10% than SAF‐5 (13.93%) and the commercial HTM spiro‐OMeTAD (19.11%). On the other hand, the SCZF‐5‐based device also has better durability in lifetime testing, indicating the newly designed SCZF by integrating carbazole into the spiro concept has good potential for developing effective HTMs.

The disparity of hole and electron behavior is a ubiquitous issue in methylammonium lead halide perovskites. The carrier mobility imbalance, which will result in a built‐in electric field thus increase the device resistance, is regarded as one of main limiting factors for the further improvement of device performance in perovskite solar cells (PSCs). Here, we realized an n‐doped organic‐inorganic hybrid perovskite by directly incorporating AgI into the CH3NH3PbI3 precursor solution, to fabricate high‐performance PSCs. AgI doping resulted in a balanced charge transporting owing to a remarkable increase in the electron mobility, which was attributed to the aligned orientation of MA+ ions owing to the Ag+‐influenced distribution of electron cloud density. Meanwhile, AgI could act as an additive to control the perovskite crystallization with improved crystallinity and film morphology. Consequently, a maximum power conversion efficiency of over 20% is achieved. The finding in this work provides a direction to fabricate high‐performance PSCs by controlling the charge balance via intensive doping technique.

High performance quasi-2D PeLEDs with maximum current efficiency of 35.5 cd A−1, by introducing α-cyclodextrin (α-CD) with a cage-type structure as an additive and TFB/PVK bilayer as a hole transport layer, are demonstrated.