High-efficiency hole transport layer free perovskite solar cells (HTL-free PSCs) with economical and simplified device structure can greatly facilitate the commercialization of PSCs. However, eliminating the key HTL in PSCs results usually in a severe efficiency loss and poor carrier transfer due to the energy-level mismatching at the indium tin oxide (ITO)/perovskite interface. In this study, we solve this issue by introducing an organic monomolecular layer (ML) to raise the effective work function of ITO with the assistance of an interface dipole created by Sn–N bonds. The energy-level alignment at the ITO/perovskite interface is optimized with a barrier-free contact, which favors efficient charge transfer and suppressed nonradiative carrier recombination. The HTL-free PSCs based on the ML-modified ITO yield an efficiency of 19.4%, much higher than those of HTL-free PSCs on bare ITO (10.26%), comparable to state-of-the-art PSCs with a HTL. This study provides an in-depth understanding of the mechanism of interfacial energy-level alignment and facilitates the design of advanced interfacial materials for simplified and efficient PSC devices.

Precursor engineering toward enhanced Voc and stability of inverted perovskite solar cells with a champion power conversion efficiency of 20.7%.

Perovskite solar cells (PSCs) have developed rapidly in the past few years. However, highly efficient PSCs prepared in ambient air have remained intractable, since the crystallization and film morphology of perovskite are highly sensitive to moisture. Here, a thermal radiated hot-cast method (THCM) to prepare high quality perovskite films in ambient air is introduced. The proposed THCM not only eliminates the temperature gradient across the perovskite film, but also forms a significantly reduced and constant relative humidity field at the local space above the substrate (ca. 6%); these conditions result in a smooth, compact, oriented perovskite film with largely reduced grain boundaries. THCM is a universal protocol, based on the application to the devices with both inverted and regular architectures, and it enables improved J-V performance with largely reduced hysteresis. The champion power conversion efficiencies of 17.2% for inverted and 19.1% for regular devices are achieved by THCM. These are comparable to the top efficiencies of fully air-processed PSCs, demonstrating that THCM is a promising protocol for commercialization of PSCs in the near future.

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Coal gasification wastewater (CGW) contains high concentrations of pollutants and varying chemical components and thus is difficult to treat. CGW slurry (CGWS), which is prepared by blending coal, CGW, and additives, is a new wastewater utilization technology that can be used to efficiently and conveniently treat CGW. This work mainly investigated the slurryability, rheology, stability, and combustion properties of CGWS prepared from Shenhua and Yima coals. Results showed that (a) the maximum solid loading of CGWS was slightly lower than that of ordinary coal-water slurry (CWS), but CGWS exhibited better pseudoplastic rheology and stability than CWS; moreover, increasing the solid loading of CGWS resulted in an increasingly pseudoplastic trend and enhanced stability; (b) CGW strengthened the combustion capacity of coke and CGWS demonstrating better ignition, burning, and burnout properties than CWS. These findings suggest that the use of CGWS technology in CGW treatment is beneficial economically and environmentally.