Organic-inorganic halide perovskites (OIHPs) have emerged as a promising semiconductor for the fabrication of efficient optoelectronic devices such as photodetectors (PDs). Among all perovskite composition, the mixed-halide MAPb(BrxI1−x)3 formulations have...

promising light absorber materials, demon strating low-cost solution processing, ease of fabrication, and outstanding optoelectronic properties. [1,2] Since the first report on the perovskite solar cells (PSCs) employing methylammonium lead iodide (MAPbI 3 ), [3] their power conversion efficiency (PCE) has now exceeded 25% for small-area cells. [4,5] The high efficiency of PSCs is achieved by tuning the perovskite layer through compositional engineering, [6][7][8] surface passivation, [9][10][11][12][13] and/or by using various additives. [14][15][16] Besides component engineering of the perovskite layer, a lot of works have been devoted to the development of efficient charge transport layers. [17][18][19][20][21] Particularly, the electron transport layers (ETLs) play an important role in realizing efficient and stable PSCs. [22,23] Thus far, titanium dioxide (TiO 2 ) is a widely applied ETL in PSCs but it suffers from low conductivity and high surface defect density. [24] Among alternative ETLs, zinc oxide (ZnO) has been regarded as a convenient candidate due to its high electron mobility and well-matched energy level with perovskite material. [25,26] This Atomic layer deposition (ALD) has been considered as an efficient method to deposit high quality and uniform thin films of various electron transport materials for perovskite solar cells (PSCs). Here, the effect of deposition sequence in the ALD process of aluminum-doped zinc oxide (AZO) films on the performance and stability of PSCs is investigated. Particularly, the surface of AZO film is terminated by diethylzinc (DEZ)/H 2 O (AZO-1) or trimethylaluminum (TMA)/H 2 O pulse (AZO-2), and investigated with surface-sensitive X-ray photoelectron spectroscopy technique. It is observed that AZO-2 significantly enhances the thermal stability of the upcoming methylammonium lead iodide (MAPbI 3 ) layer and facilitates charge transport at the interface as evidenced by photoluminescence spectroscopes and favorable interfacial band alignment. Finally, planar-type PSC with AZO-2 layer exhibits a champion power conversion efficiency of 18.09% with negligible hysteresis and retains 82% of the initial efficiency after aging for 100 h under ambient conditions (relative humidity 40 ± 5%). These results highlight the importance of atomic layer engineering for developing efficient and stable PSCs.

Additive engineering in perovskites precursor solution is one of the most effective methods to fabricate high-quality perovskite films. Finding proper additives for morphology improvement and passivation of the perovskite defects is critical to fabricate highly efficient and stable perovskite solar cells (PSCs). In this work, 1,3-disubstituted urea additives are employed to study the effect of different substituents at −NH moiety on the quality of the perovskite layer and device performance. By adding 1,3-diphenyl urea (Ph-urea) or 1,3-di(tert-butyl)urea (tBu-urea) into the precursors, the crystallization process leads to the formation of perovskite films with larger grains and lower defect densities as compared to the nonsubstituted urea additive. Using density functional theory (DFT) calculations and experimental spectroscopic measurements, we found that the selected 1,3-disubstituted ureas are prone to form stronger coordination interaction with undercoordinated Pb2+ ions than the urea. Applying this additive engineering to the devices reduced the current density–voltage (J–V) hysteresis and improved the photovoltaic performance, resulting in maximum power conversion efficiencies of 21.7 and 21.2% for the Ph-urea and tBu-urea modified devices, respectively. In addition, the device with Ph-urea enhanced long-term stability, where it remains at 90% of its initial efficiency, while the device with tBu-urea degrades fast reaching 20% of its initial efficiency after aging for 90 days due to the high moisture permeability of tBu-urea.