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A novel ball milling method was used to prepare TiO2 ETMs at RT ∼ 30 °C for large and small area perovskite solar cells.

A novel ball milling method was used to prepare TiO2 ETMs at RT ∼ 30 °C for large and small area perovskite solar cells.

An exquisite, engineering of two poor hole transporting materials (HTMs, SnO, and PDTON) to form an excellent double‐layered HTL (SnO/PDTON) for inverted tin‐perovskite solar modules (TPSMs) is developed. SnO/PDTON has better photovoltaic performance than the commonly used PEDOT:PSS HTM when large‐area TPSMs are fabricated. Thermally evaporated SnO (that is a simple, available oxide with high hole mobility, good transparency, and adjustable frontier orbitals energy levels) film is used as a main hole transporting layer (HTL). Amphiphilic polymer PDTON (having the amine and ether groups on the side chains) film is used as a Co‐HTL, cross‐linker, passivator, and interface modification agent, as unveiled various physicochemical studies. Double‐layered SnO/PDTON with a flat morphology and good affinity toward perovskite precursor solution creates also a proper surface for depositing large‐area, high‐quality TPsk film. Therefore, TPSM (25.2 cm2 active area on 10 cm × 10 cm ITO substrate) based on double‐layered SnO/PDTON HTL achieving an efficiency over 10% with a negligible current hysteresis is reported for the first time. This study emphasizes not only the exquisite design of combining the specific characteristics of two prosaic HTMs to become a good double‐layered HTL but also gives a direction toward fabricating TPSMs to be applied in all‐perovskite tandem solar module. [ABSTRACT FROM AUTHOR]

Low‐temperature sol‐gel prepared ZnCo2O4 spinel‐based thin films are developed as high‐performance hole transporting layer (HTL) for coating perovskite film (NA‐Psk) from the basic MAPbI3/ACN/CH3NH2 solution in air without using anti‐solvent. Inverted PSC based on 2 mole% (vs Zn) Cu2+ doped ZnCo2O4 (2%Cu@ZnCo2O4) HTL and NA‐Psk absorber exhibit the maximum power conversion efficiency (PCE) of 20.0% with no current hysteresis while the cell based on ZnCo2O4 and PEDOT:PSS HTL (using NA‐Psk absorber) achieves the PCE of 15.79% and 12.3% with a current hysteresis index of 9.8% and 32.4%, respectively. Without encapsulation, PSCs based on 2%Cu@ZnCo2O4, ZnCo2O4, and PEDOT:PSS HTLs maintain 90%, 77%, and 12%, respectively of the original efficiency by standing in ambient atmosphere (temperature: 20–25 °C, RH:30%–40%) for 1800 h. Large area (10 cm × 10 cm substrate) perovskite mini‐module (PSM) with PCE over 15% is also demonstrated by using sol‐gel prepared 2%Cu@ZnCo2O4 HTL. The poor photovoltaic performance of PEDOT:PSS HTL is due to the basic MAPbI3/ACN/CH3NH2 solution will deprotonate the acidic PEDOT:PSS to reduce its conductivity whereas ZnCo2O4 HTL are not affected by basic perovskite precursor solution. [ABSTRACT FROM AUTHOR]

The oxide/nitride passivation and the flip‐chip package technology are developed for the perovskite solar cells. The heat resulting from the physical vapor deposition decomposes the active perovskite layer and degrades the efficiency of the perovskite solar cells down by more than 45%. Remarkably, with Si‐nitride passivation processed by plasma‐enhanced vapor deposition, the efficiency of the perovskite solar cell only decays about 9.1%. It is because that the plasma‐enhanced vapor deposition causes much less external energy on the perovskite solar cell. Using the exponential efficiency‐decay curves of the flip‐chip packaged perovskite solar cells, the characteristic time of the reliability‐tested solar cell can be calculated to be 145.8, 390.7, and 4864 h for air‐ambient, glove chamber, and water‐ambient tests, respectively. It is concluded that the concentration of O2(g) in the reliability test ambient is the root cause for the efficiency degradation of the perovskite solar cells. The low mobility of O2(g) under the water‐ambient reliability test results in the low probability of the adsorption of O2(g) on the surface of the flip‐chip package, which is the key factor for the least efficiency degradation of the perovskite solar cells among the three reliability tests. [ABSTRACT FROM AUTHOR]

Room‐temperature‐processed TiO2 (R‐Lt‐TiO2) electron transporting layers (ETLs) possess low conductivity and connectivity, resulting in poor photovoltaic performance. Herein, an ethanol (EtOH)‐soluble, highly conducting fullerene derivative, C60RT6, was used as an additive for Lt‐TiO2 ETLs. Room‐temperature processed nanocomposite ETL (R‐Fu/Lt‐TiO2) is prepared simply by spin coating a C60RT6 and G‐TiO2 NPs (TiO2 nanoparticle prepared by grinding the bulk TiO2 powder) mixture. R‐Fu/Lt‐TiO2 has better aligned with the frontier orbitals of the FAxMA1−xPbI3, better continuity, conductivity, flatness, and higher surface hydrophilicity compared to Lt‐TiO2 ETL. Perovskite films spin coated on R‐Fu/Lt‐TiO2 ETLs also have slightly larger grains and thickness compared to those deposited on Lt‐TiO2. Perovskite solar cells (PSCs) based on a R‐Fu/Lt‐TiO2 ETL possess higher power conversion efficiency (PCE, up to 20% on glass substrate), less (negligible) current hysteresis, and better long‐term stability compared to those using R‐Lt‐TiO2 as an ETL. The flexible PSC (used indium tin oxide/polyethylene terephthalate (ITO/PET) as a substrate) with a R‐Fu/Lt‐TiO2 ETL achieves a PCE of 18.06% and retains 90% of the initial PCE after 500 bending cycles with a bending radius of 6 mm. The PCE of the flexible cell with a Lt‐TiO2 ETL is only 8.2%, and loses 60% of the initial value after 500 bending cycles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]