Highly Efficient Perovskite Light-Emitting Diodes Incorporating Full Film Coverage and Bipolar Charge Injection

Abstract

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.

Metal Halide Perovskites: From Crystal Formations to Light‐Emitting‐Diode Applications

“…In MHP NCs, electron‐hole pairs can be easily dissociated in film states due to the close proximity of the NCs; this process decreases the LE. Inspired by the progress of OLEDs, we suggest that dopant‐in‐host (MHP PC or NC‐in‐organic) systems have potential to improve the EL efficiency of PeLEDs because these systems may further reduce the grain size, passivate surface defects in grain boundaries, and prevent dissociation of electron‐hole pairs. Inspired by the progress of QD LEDs, core–shell or gradient–alloy (MHP NC–inorganic) system may also further confine the electron‐hole pairs in their core perovskites and improve the EL efficiency.…”

“…Mixing two organic molecules (PEO with polyvinylpyrrolidone (PVP) or PVK with 1,3,5‐tris(1‐phenyl‐1 H ‐benzimidazol‐2‐yl)benzene (TPBI)) can further improve the uniformity of MHP PC films, facilitate charge injection from the HIL/EML and EML/EIL interfaces due to the in situ‐formed p–i–n junction in the EML or efficient charge‐transport properties of PVK (hole mobility ≈ 4.8 × 10 −9 cm 2 V −1 s −1 ) and TPBI (electron mobility ≈ 5.14 × 10 −5 cm 2 V −1 s −1 ), and thus achieve an efficient EL in PeLEDs (EQE ≈ 5.7%, power efficiency PE ≈ 14.1 lm W −1 , L ≈ 593 178 cd m −2 for PeLEDs based on PEO:PVP:CsPbBr 3 ; EQE ≈ 2.28%, CE ≈ 9.45 cd A −1 , L ≈ 7263 cd m −2 for PeLEDs based on PEO:PVP:MAPbBr 3 ).…”

In Situ Fabricated Perovskite Nanocrystals: A Revolution in Optical Materials

“…[68] It is also possible to blend the polymeric charge transporting materials such as polyvinyl carbazole (PVK) [134,135] into the perovskite films to control the film morphology and facilitate the charge transport.…”

High Photoluminescence Quantum Yields in Organic Semiconductor–Perovskite Composite Thin Films

“…Radiative recombination and hence PLQY can be substantially enhanced through spatial confinement of charges, which can be obtained in passivated perovskite nanostructures, such as colloidal nanocrystals . Another way of obtaining nanostructured perovskites is the use of a scaffold, which can be a metal oxide, a polymer, or even a small molecular weight compound (small molecules) that can be blended and solution‐processed with the perovskite precursors . In this way, the crystal/grain growth of the perovskite is limited by of the dielectric scaffold, and highly luminescent perovskite composite films can be readily prepared.…”

“…[12][13][14] Another way of obtaining nanostructured perovskites is the use of as caffold, which can be am etal oxide, [15,16] ap olymer, [17][18][19][20][21][22] or even a small molecular weightc ompound (smallm olecules) that can be blended and solution-processed with the perovskite precursors. [23,24] In this way,t he crystal/graing rowth of the perovskite is limited by of the dielectric scaffold, and highly luminescent perovskite composite films can be readily prepared. Onei mportant condition that must be met to ensure ah igh PLQY is the passivation of perovskite crystals.…”