Reciprocally Photovoltaic Light-Emitting Diode Based on Dispersive Perovskite Nanocrystal

Synergistic Optimization of Buried Interface by Multifunctional Organic-Inorganic Complexes for Highly Efficient Planar Perovskite Solar Cells

For the further improvement of the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs), the buried interface between the perovskite and the electron transport layer is crucial. However, it is challenging to effectively optimize this interface as it is buried beneath the perovskite film. Herein, we have designed and synthesized a series of multifunctional organic-inorganic (OI) complexes as buried interfacial material to promote electron extraction, as well as the crystal growth of the perovskite. The OI complex with BF4- group not only eliminates oxygen vacancies on the SnO2 surface but also balances energy level alignment between SnO2 and perovskite, providing a favorable environment for charge carrier extraction. Moreover, OI complex with amine (- NH2) functional group can regulate the crystallization of the perovskite film via interaction with PbI2, resulting in highly crystallized perovskite film with large grains and low defect density. Consequently, with rational molecular design, the PSCs with optimal OI complex buried interface layer which contains both BF4- and -NH2 functional groups yield a champion device efficiency of 23.69%. More importantly, the resulting unencapsulated device performs excellent ambient stability, maintaining over 90% of its initial efficiency after 2000 h storage, and excellent light stability of 91.5% remaining PCE in the maximum power point tracking measurement (under continuous 100 mW cm-2 light illumination in N2 atmosphere) after 500 h.

Self-Generated Buried Submicrocavities for High-Performance Near-Infrared Perovskite Light-Emitting Diode

Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency (LOCE) for planar perovskite light-emitting diodes (PeLEDs). In this work, we employ phenethylammonium iodide (PEAI) to trigger the Ostwald ripening for the downward recrystallization of perovskite, resulting in spontaneous formation of buried submicrocavities as light output coupler. The simulation suggests the buried submicrocavities can improve the LOCE from 26.8 to 36.2% for near-infrared light. Therefore, PeLED yields peak external quantum efficiency (EQE) increasing from 17.3% at current density of 114 mA cm-2 to 25.5% at current density of 109 mA cm-2 and a radiance increasing from 109 to 487 W sr-1 m-2 with low rolling-off. The turn-on voltage decreased from 1.25 to 1.15 V at 0.1 W sr-1 m-2. Besides, downward recrystallization process slightly reduces the trap density from 8.90 × 1015 to 7.27 × 1015 cm-3. This work provides a self-assembly method to integrate buried output coupler for boosting the performance of PeLEDs.

High Efficiency Near-Infrared Perovskite Light Emitting Diodes With Reduced Rolling-Off by Surface Post-Treatment

The rolling-off phenomenon of device efficiency at high current density caused by quenching of luminescence in perovskite light-emitting diodes (PeLED) is challenging to be solved. Here, 2-amino-5-iodopyrazine (AIPZ) is dissolved in a mixed solvent of chlorobenzene (CB)/isopropanol (IPA) (7:3 volume ratio) for surface post-treatment of FAPbI₃ perovskite film. The interaction of AIPZ and perovskite surface not only balances the charge injection but also passivates defects to enhance radiative recombination in PeLED. Therefore, the PeLED champion yields peak external quantum efficiency reaching 23.2% at the current density of 45 mA cm^-2 with a radiance brightness of 290 W sr^-1 m^-2 . More importantly, the rolling-off of device efficiency is significantly reduced. The lowest rolling-off devices can maintain 80% of peak EQE (22.1%) at a high current density of 460 mA cm^-2 , whereas the control device only retains 25% of the peak EQE value. This work provides an effective strategy to improve performance and reduce the EQE rolling-off of PeLED for practical application.

Improved Performance of All-Inorganic Perovskite Light-emitting Diodes via Nanostructured Stamp Imprinting

Halide perovskites are emerging emitters with excellent optoelectronic properties. Contrary to the large grain fabrication goal in perovskite solar cells, perovskite light-emitting diodes (PeLEDs) based on small grain enable efficient radiative recombination because of relatively higher charge carrier densities due to spatial confinement. However, achieving small-sized grain growth with superior crystal quality and film morphology remains a challenge. In this work, we demonstrated a nanostructured stamp thermal imprinting strategy to boost the surface coverage and improve the crystalline quality of CsPbBr₃ film, particularly confine the grain size, leading to the improvement of luminance and efficiency of PeLEDs. We improved the thermal imprinting process utilizing the nanostructured stamp to selectively manipulate the nucleation and growth in the nanoscale region and acquire small-sized grain accompanied by improved crystal quality and surface morphology of the film. By optimizing the imprinting pressure and the period of the nanostructures, appropriate grain size, high surface coverage, small surface roughness and improved crystallization could be achieved synchronously. Finally, the maximum luminance and efficiency of PeLEDs achieved by nanostructured stamp imprinting with a period of 320 nm are 67600 cd/m² and 16.36 cd/A, respectively. This corresponds to improvements of 123 % in luminance and 100 % in efficiency, compared to that of PeLEDs without the imprinting.