By the introduction of an organic silane self-assembled monolayer, an interface-engineering approach is demonstrated for hole-conductor-free, fully printable mesoscopic perovskite solar cells based on a carbon counter electrode. The self-assembled silane monolayer is incorporated between the TiO2 and CH3NH3PbI3, resulting in optimized interface band alignments and enhanced charge lifetime. The average power conversion efficiency is improved from 9.6% to 11.7%, with a highest efficiency of 12.7%, for this low-cost perovskite solar cell.

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Additives are widely adopted for efficient, stable, and hysteresis‐free perovskite solar cells and play an important role in various breakthroughs of perovskite solar cells (PSCs). Herein the various additives adopted for PSCs are reviewed and their functioning mechanism and influence on device performance is described. The main roles of additives, modulating morphology of perovskite films, stabilizing phase of formamidinium (FA) and cesium (Cs)‐based perovskites, adjusting energy level alignment in PSCs, suppressing nonradiative recombination in perovskites, eliminating hysteresis, enhancing operational stability of PSCs, are summarized.

Perovskite solar cells (PSCs) usually suffer an anomalous hysteresis in current-voltage measurements that leads to an inaccurate estimation of the device efficiency. Although ion migration, charge trapping/detrapping and accumulation have been proposed as a basis for the hysteresis, the origin of hysteresis has not been apparently unraveled. Herein we reported a tunable hysteresis effect based uniquely on open-circuit voltage variations in printable mesoscopic PSCs with a simplified triple-layer TiO2/ZrO2/Carbon architecture. The electrons are collected by the compact TiO2/mesoporous TiO2 (cTiO2/mp-TiO2) bilayer, and the holes are collected by the carbon layer. By adjusting the spray deposition cycles for the cTiO2 layer, we achieved hysteresis-normal, hysteresis-free, and hysteresis-inverted PSCs. Such unique trends of tunable hysteresis are analysed by considering the polarization of the TiO2/perovskite interface, which can accumulate positive charges reversibly. Successfully tuning the hysteresis effect clarifies the critical importance of the c-TiO2/perovskite interface in controlling the hysteretic trends observed, providing important insights towards the understanding of this rapidly developing photovoltaic technology.

Perovskite solar cells (PSCs) have achieved high power conversion efficiency on the lab scale, rivaling the other commercialized photovoltaic technologies. However, stability issues have made it difficult for PSCs to achieve comparable or practical lifetimes in outdoor applications. Here, three different types of hot melt films (polyurethane, PU; polyolefin, POE; and ethylene vinyl acetate, EVA) together with glass sheets are employed to encapsulate printable PSCs. The influence of thermal stress and the encapsulation (lamination) process on cell performance is investigated. It is found that POE and EVA, which are the typical encapsulants for silicon and thin film solar cells, are not suitable for the encapsulation of PSCs due to a high laminating temperature (>130 °C) or corrosion of the perovskite absorber. By contrast, encapsulation with PU can be carried out at a relatively mild temperature of 80 °C, and significantly enhance the thermal stability of the cells. When this encapsulation method is applied to largearea (substrate area 100 cm 2 ) printable PSC submodules, the submodules can maintain 97.52% of the initial efficiency after 2136 h under outdoor conditions (location: 39°19′48″N 114°37′26″E). This work demonstrates the potential of industrially relevant encapsulation techniques to enable the commercial viability of PSCs.

Mixed‐anion perovskite CH3NH3PbI(3−x)(BF4)x has been developed and optimized to enable a highly efficient hole‐conductor‐free fully printable mesoscopic solar cell. The employment of BF4− in hybrid organic–inorganic halide perovskite significantly improves its optical and electric properties, such as light harvesting ability, carrier concentration, and conductivity, leading to an enhanced power conversion efficiency of 13.24%.

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Lead halide perovskite solar cells have recently emerged as a very promising photovoltaic technology due to their excellent power conversion efficiencies; however, the toxicity of lead and the poor stability of perovskite materials remain two main challenges that need to be addressed. Here, for the first time, we report a lead-free, highly stable CHNHCuBrI compound. The CHNHCuBrI films exhibit extraordinary hydrophobic behavior with a contact angle of ∼90°, and their X-ray diffraction patterns remain unchanged even after 4 h of water immersion. UV/vis absorption spectrum shows that CHNHCuBrI compound has an excellent optical absorption over the entire visible spectrum. We applied this copper-based light absorber in printable mesoscopic solar cell for the initial trial and achieved a power conversion efficiency of ∼0.5%. Our study represents an alternative pathway to develop low-toxic and highly stable organic-inorganic hybrid materials for photovoltaic application.