Perovskite Quantum Dots as Multifunctional Interlayers in Perovskite Solar Cells with Dopant-Free Organic Hole Transporting Layers

Abstract

Perovskite solar cells (PSCs) with organic hole transporting layers (o-HTLs) have been widely studied due to their convenient solution processing, but it remains a big challenge to improve the hole mobilities of commercially available organic hole transporting materials without ion doping while maintaining the stability of PSCs. In this work, we demonstrated that the introduction of perovskite quantum dots (QDs) as interlayers between perovskite layers and dopant-free o-HTLs (P3HT, PTAA, Spiro-OMeTAD) resulted in a significantly enhanced performance of PSCs. The universal role of QDs in improving the efficiency and stability of PSCs was validated, exceeding that of lithium doping. After a deep examination of the mechanism, QD interlayers provided the multifunctional roles as follows: (1) passivating the perovskite surface to reduce the overall amount of trap states; (2) promoting hole extraction from perovskite to dopant-free o-HTLs by forming cascade energy levels; (3) improving hole mobilities of dopant-free o-HTLs by regulating their polymer/molecule orientation. What is more, the thermal/moisture/light stabilities of dopant-free o-HTLs-based PSCs were greatly improved with QD interlayers. Finally, we demonstrated the reliability of the QD interlayers by fabricating large-area solar modules with dopant-free o-HTLs, showing great potential in commercial usage.

Perovskite Quantum Dots in Solar Cells

“…Till now, CsPbI 3 PQDs, [ 118 , 119 ] CsPbBr 3 PQDs, [ 132 ] CsPbI x Br 3− x PQDs, [ 120 , 121 ] MAPbI 2.1 Br 0.9 PQDs, [ 122 ] Cs 0.57 FA 0.43 PbI 3 PQDs, [ 123 ] Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 PbBr 3 PQDs [ 124 ] were introduced between the perovskite layers and the HTLs as interface layers, markedly enhancing the PCE and stability of PSCs. By virtue of their multifunctional properties, [ 139 ] the key reason was revealed.…”

“…For example, CsPbI 1.85 Br 1.15 PQDs was used between perovskite and kinds of dopant‐free HTL interfaces which was also extended to large‐area solar modules that the solar module presented an obvious upgrade in V OC and FF with the PQD interlayer and 17.6% efficiency was achieved at an 18.0 cm 2 active area. [ 121 ] Moreover, Cs 0.57 FA 0.43 PbI 3 PQDs were deposited on the surface of Cs‐lean FAPbI 3 perovskite films to circumvent the issue that only a limited amount of Cs can be alloyed owing to the intrinsically low solid‐solubility of Cs. [ 123 ] The PQDs modification not only improves the charge dynamics in the devices but also significantly enhances the ambient stability.…”

Critical Role of Removing Impurities in Nickel Oxide on High‐Efficiency and Long‐Term Stability of Inverted Perovskite Solar Cells

“…However, their complicated fabrication process, intrinsic chemical volatility, poor stability, and high cost hinder the large‐scale application toward commercialization. By comparison, several inorganic HTMs such as CuSCN, [7, 8] NiO x , [9–12] CuI, [13, 14] VO x and WO 3 have been used as substitutes for organic HTMs [15–17] . Among those, NiO x has attracted extensive attention because of its high optical transmittance, appropriate work function and inherent stability [18–22] .…”

“…By comparison, several inorganic HTMs such as CuSCN, [7,8] NiO x , [9][10][11][12] CuI, [13,14] VO x and WO 3 have been used as substitutes for organic HTMs. [15][16][17] Among those, NiO x has attracted extensive attention because of its high optical transmittance, appropriate work function and inherent stability. [18][19][20][21][22] Currently, NiO x HTL can be produced by sputtering, electrodeposition, or pulsed laser deposition technologies.…”

Inorganic CsPbBr3 Perovskite Nanocrystals as Interfacial Ion Reservoirs to Stabilize FAPbI3 Perovskite for Efficient Photovoltaics

“…[18,26] So far, the incorporation of perovskite nanocrystals to the bulk perovskite film of solar cells has shown good potential on improving the band alignment in cell structure, [27][28][29] passivating the bulk and surface defects, [30,31] and enhancing overall device performances. [32,33] However, the mechanisms that govern the NC modification strategy are still unclear and need more systematic investigations. [34,35] For example, many of the previous studies have interpreted the NC incorporation as a one-way process.…”