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A polymer-based hole-transporting layer (HTL) with a tunable work function and highest occupied molecular orbital (HOMO) position was demonstrated to effectively optimize the anode junctions of optoelectronic devices. Herein, the perfluorinated ionomer (PFI) was utilized to realize the synthesis of a well-dispersed poly(3,4-ethylene dioxythiophene) (PEDOT) colloid solution, which could be subsequently cast into an efficient HTL. According to the time-of-flight secondary-ion mass spectroscopy and ultraviolet photoelectron spectroscopy analysis, a uniform, interpenetrating PEDOT network with a deep-lying HOMO position could be obtained in the PEDOT:PFI layer. For solar cells, since a deep-lying HOMO position of the HTL was favorable for minimizing the hole injection barrier, a superior organic photovoltaic efficiency of 15.1% and a perovskite solar cell efficiency of 17.8% were achieved. As for organic photodetectors, a deep-lying HOMO position of the HTL was able to reduce the dark current density (JD) by blocking the leakage current under a reverse bias. Utilizing the PEDOT:PFI with an optimized PFI content, an extremely low JD of 6.2 nA cm−2 with an external quantum efficiency of 67% at 1000 nm wavelength was achieved, which sets a benchmark for the emerging near infrared sensing technologies.

Technological implementation of organolead trihalide perovskite (OTP) photovoltaics requires suppression of the surface ionic defects and grain boundaries of OTP films. These surface ionic defects have a detrimental effect on the power conversion efficiency (PCE), are notorious for introducing hysteresis into the current density–voltage (J–V) characteristics, and decrease the stability of perovskite solar cells (PSCs). Here, we report the use of core/shell quantum dots (QDs) as passivation layers on the OTP surfaces to decrease the trap density and, simultaneously, stabilize the OTP chemical structure and extend the charge carrier lifetime. Density functional theory (DFT) calculations indicated that the OTP surface defects and grain boundaries were effectively suppressed by the presence of the CdSe/ZnS QDs. We attribute the lower trap density of the OTP to the Se2− anions from the CdSe/ZnS passivation layer, inducing van der Waals interactions between the organic and inorganic components of the framework. For PSCs featuring CdSe/ZnS QD passivation, the PCE reached close to 20% with diminishing hysteresis of the J–V characteristics and fill factor (FF) of 81.44%. Moreover, the PSCs incorporating the CdSe/ZnS QD passivation layer exhibited long-term stability, retaining 75 and 80% of their initial performance after 2400 and 720 h, respectively. This facile interfacial strategy appears highly applicable for preparing high-performance durable OTP-based high optoelectronic devices.

Anatase titanium dioxide (an-TiO2) is often used as the electron transporting material (ETM) in planar-heterojunction perovskite solar cells (PSCs) because of its excellent semiconductor characteristics, outstanding optical transmittance, and suitable band structure. Herein, we report an inexpensive method for mass-scale production of TiO2 ETMs at room temperature (RT ∼ 30 °C), involving the grinding of large clumps of an-TiO2 to form a suspension of TiO2 nanoparticles (NPs) in isopropyl alcohol for meso-superstructured PSCs. This process does not involve any chemical synthesis; it is a purely physical process. The lowest unoccupied molecular orbital (LUMO) of ground an-TiO2 NPs, estimated using ultraviolet photoelectron spectroscopy (UPS), was ca. 4.06 eV, which is a salient feature for the active layer. A regular perovskite solar cell (PSC) based on a CH3NH3PbI3 absorber and ground an-TiO2 ETL exhibited a champion power conversion efficiency (PCE) of 17.43% with an active area of 0.1 cm2. The same ground an-TiO2 NPs were used to fabricate a large-area (designated area: 25.2 cm2) PSC and a PCE of 14.19% was achieved. PSC devices incorporating the ground an-TiO2 NP ETLs exhibited an attractive long-term device stability, with the PCE retaining approximately 85% of the initial values after 80 days.