Annealing-Insensitive, Alcohol-Processed MoO_x Hole Transport Layer for Universally Enabling High-Performance Conventional and Inverted Organic Solar Cells

Abstract

At present, most solution-processed molybdenum oxide (s-MoO x ) hole transport layers (HTLs) are still mainly used in conventional organic solar cells (OSCs) but unsuitable for inverted OSCs. Herein, we demonstrate for the first time an annealing-insensitive, alcohol-processed MoO x HTL that can universally enable high-performance conventional and inverted OSCs. The s-MoO x HTL is spin-coated from the MoO x nanoparticle dispersion in alcohol, where the MoO x nanoparticles are synthesized by simple nonaqueous pyrolysis conversion of MoO2(acac)2. The MoO x nanoparticles possess uniform and very small sizes of less than 5 nm and can be well dispersed in alcohol, so the s-MoO x HTLs on ITO and active layer both show an overall uniform and smooth surface, suitable for conventional and inverted OSCs. In addition, the s-MoO x HTL possesses decent optical transmittance and appropriate work function. Utilizing the s-MoO x HTL annealed between room temperature and 110 °C and PM6:Y6 active layer, the conventional OSCs show an excellent power conversion efficiency (PCE) of 16.64–17.09% and the inverted OSCs also show an excellent PCE of 15.74–16.28%, which indicate that the s-MoO x HTL could be annealing-insensitive and universal for conventional and inverted OSCs. Moreover, conventional and inverted OSCs with the s-MoO x HTLs annealed at 80 °C both exhibit optimal PCEs of 17.09 and 16.28%, respectively, which are separately superior than that of the PEDOT:PSS-based conventional OSCs (16.94%) and the thermally evaporated MoO3 (e-MoO3)-based inverted OSCs (16.03%). Under light soaking and storage aging in air, the unencapsulated inverted OSCs based on the s-MoO x HTL show similarly excellent ambient stability compared to the e-MoO x -based devices. In addition, the s-MoO x HTL also shows a universal function in conventional and inverted OSCs with PBDB-T:ITIC and PM6:L8-BO active layers. Notably, the s-MoO x -based conventional and inverted OSCs with the PM6:L8-BO active layer exhibit very excellent PCEs of 18.21 and 17.12%, respectively, which are slightly higher than those of the corresponding PEDOT:PSS-based device (18.17%) and e-MoO3-based device (17.00%). The annealing-insensitive, alcohol-processed MoO x HTL may be very promising for flexible and large-scale processing conventional/inverted OSCs.

Tetrabutylammonium Bromide Functionalized Ti3C2Tx MXene as Versatile Cathode Buffer Layer for Efficient and Stable Inverted Perovskite Solar Cells

“…Figure 5h displays the fitting curves of V oc and P light according to the Equation of V oc ∝ nkT/q lnP light , where n is the ideal factor, k is the Boltzmann constant, T is the Kelvin temperature, and q is the elementary charge. [40] When the n value is close to 2, the trap-assisted Shockley-Read-Hall recombination is dominant in the devices. [41] Compared with the n value (1.87) of the control device without CBL, all of PVSCs employed CBL show a lower fitted slope.…”

A robust and thickness-insensitive hybrid cathode interlayer for high-efficiency and stable inverted organic solar cells

“…3d shows the electrostatic surface potential (ESP) distributions for PDINN and a repeating unit of PFOPy at the B3LYP/6-31G(d,p) level using density functional theory (DFT) calculations. The distinct differences in the energy levels 32,[34][35][36] Compared with the PFOPy modied ITO, the PFOPy-N modied ITO can form better energy level alignment with acceptors, which is benecial for electron transport and extraction from the active layer to the ITO cathode.…”

“…5c, the PFOPy and PFOPy-N based devices both show weak bimolecular recombination with a values of 0.96 and 0.97, respectively. Charge extraction properties of inverted OSCs can be evaluated by analyzing the relationship between the photocurrent density (J ph ) versus the effective voltage (V eff ) of the devices, 32,34 and the J ph -V eff curves of the devices with PFOPy and PFOPy-N CILs are shown in Fig. 5d.…”

“…1 and S1 † displays the chemical structures of active layer materials, including PBDB-T, PM6, ITIC, Y6, L8-BO, and BTP-eC9. 32,[34][35][36] The PFOPy-N CIL retains the crosslinking characteristic of PFOPy and shows strong solvent resistance properties. The n-type self-doping characteristic of PDINN and the charge transfer between PFOPy and PDINN synergistically facilitate electron transport in the PFOPy-N CIL.…”

Solution-processed and thickness-insensitive hole transport layer for high efficiency organic solar cells

“…25,26 Several transition metal oxides, such as nickel oxide (NiO x ), vanadium oxide (V 2 O 5 ) and molybdenum oxide (MoO x ), have been investigated as HTL materials owing to their excellent optical and electrical characteristics. [27][28][29][30][31] Among them, MoO x possesses superior hole extracting/electron blocking properties and has been widely utilized as HTLs in inverted OSCs. However, some drawbacks still limit its practical application in solutionprocessed OSCs.…”