Dual Interfacial Design for Efficient CsPbI₂Br Perovskite Solar Cells with Improved Photostability

Abstract

A synergic interface design is demonstrated for photostable inorganic mixed‐halide perovskite solar cells (PVSCs) by applying an amino‐functionalized polymer (PN4N) as cathode interlayer and a dopant‐free hole‐transporting polymer poly[5,5′‐bis(2‐butyloctyl)‐(2,2′‐bithiophene)‐4,4′‐dicarboxylate‐alt‐5,5′‐2,2′‐bithiophene] (PDCBT) as anode interlayer. First, the interfacial dipole formed at the cathode interface reduces the workfunction of SnO2, while PDCBT with deeper‐lying highest occupied molecular orbital (HOMO) level provides a better energy‐level matching at the anode, leading to a significant enhancement in open‐circuit voltage (Voc) of the PVSCs. Second, the PN4N layer can also tune the surface wetting property to promote the growth of high‐quality all‐inorganic perovskite films with larger grain size and higher crystallinity. Most importantly, both theoretical and experimental results reveal that PN4N and PDCBT can interact strongly with the perovskite crystal, which effectively passivates the electronic surface trap states and suppresses the photoinduced halide segregation of CsPbI2Br films. Therefore, the optimized CsPbI2Br PVSCs exhibit reduced interfacial recombination with efficiency over 16%, which is one of the highest efficiencies reported for all‐inorganic PVSCs. A high photostability with a less than 10% efficiency drop is demonstrated for the CsPbI2Br PVSCs with dual interfacial modifications under continuous 1 sun equivalent illumination for 400 h.

Cesium Lead Inorganic Solar Cell with Efficiency beyond 18% via Reduced Charge Recombination

“…[14] Furthermore, from the relationship between V OC and light intensity shown in Figure S4b (Supporting Information), it can be seen that the SnO 2 -based device shows a slope of 1.94 K B T/q, while LiF-introduced device shows a smaller slope of 1.59 K B T/q. [30] Thus, these results further confirmed that the optimized SnO 2 layer could effectively suppress the recombination in PSCs. [30] Thus, these results further confirmed that the optimized SnO 2 layer could effectively suppress the recombination in PSCs.…”

“…[27] Recently, an outstanding efficiency of 17.06% with V OC of 1.1 V was realized by Zhao et al via using HPbI 3 as a precursor combined with the PTABr surface modification. [10,14] Most recently, Yip et al applied PN4N as cathode interlayer to reduce the work function of the SnO 2 electron transporting layer (ETL) for tuning the electron extraction property and combing with poly[5,5′-bis(2-butyloctyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-5,5′-2,2′-bithiophene] (PDCBT) as hole transporting layer, leading to a significant enhancement in V OC of the CsPbI 3-x Br x PVSCs from 1.06 to 1.3 V [30] ; however, the V oc loss is still as high as 0.62 V .Here, we develop an inorganic shunt-blocking layer lithium fluoride (LiF) between SnO 2 and CsPbI 3-x Br x perovskites, which push forward the conduction band of the electron transport Cesium-based inorganic perovskite solar cells (PSCs) are promising due to their potential for improving device stability. [29] It can be found that the opencircuit voltage loss (V oc loss) is still the main reason of low performance of inorganic perovskite solar cells, which strongly related to energy band matching and defects at the interface or in the bulk of perovskite.…”

Controlled n‐Doping in Air‐Stable CsPbI2Br Perovskite Solar Cells with a Record Efficiency of 16.79%

“…In order to improve the V oc of a CsPbI 2 Br device, Chen et al applied a gradient thermal annealing and antisolvent method to retard the crystallization process of CsPbI 2 Br film, resulting in a uniform and high‐quality perovskite film and an improved V oc of 1.23 V 19. Tian et al introduced an amino‐functionalized polymer, PN4N, as a novel cathode interlayer, demonstrating that the PN4N interlayer is conducive to the quality of the perovskite film, and the conduction‐band alignment between the electron transport layer and perovskite resulted in an improved V oc of 1.30 V 20. Our group has developed a precursor engineering method using Pb(Ac) 2 as an additive to enhance the built‐in potential in CsPbI 2 Br PSCs, leading to a significant enhancement of V oc from 1.22 to 1.30 V 21.…”

Tailoring C60 for Efficient Inorganic CsPbI2Br Perovskite Solar Cells and Modules

“…We investigated the peaks of F1s, C1s, and B1s in the XPS spectra (Figure c). It can be observed that the C1s peak from C 60 is shifted toward higher binding energy while the F1s and B1s peaks belonging to the TPFPB are shifted to lower binding energy after the incorporation of TPFPB into C 60 film, suggesting that the electron density around the boron atom was increased, due to the donation of electrons to the carbon atom . Moreover, the HOMO and LUMO energy levels of C 60 without or with TPFPB doping have been calculated to understand the changes of frontier electron orbitals, as the molecular orbital configurations are depicted in Figure d.…”